Datasets:

sidovic
/

LearningQ-qg

LearningQ, a challenging educational question generation dataset containing over 230K document-question pairs by [Guanliang Chen, Jie Yang, Claudia Hauff and Geert-Jan Houben]. It includes 7K instructor-designed questions assessing knowledge concepts being taught and 223K learner-generated questions seeking in-depth understanding of the taught concepts. This new version collected and corrected from over than 50000 error and more than 1500 type of error by Sidali Lamri

Use the dataset

from datasets import load_dataset
lq_dataset = load_dataset("sidovic/LearningQ-qg")
lq_dataset["train"][1]
len(lq_dataset["train"]),len(lq_dataset["validation"]),len(lq_dataset["test"])

Supported Tasks and Leaderboards

[Question generation]

Languages

[English]

Dataset Structure

Data Instances

An example of example looks as follows.

{
    
    "context": "This is a test context.",
    "questionsrc": "test context",
    "question": "Is this a test?"
}

Data Fields

The data fields are the same among all splits.

context: a string feature.
questionsrc: a string feature.
question: a string feature.

Data Splits

name	train	validation	test
LearningQ	188660	20630	18227

Dataset Creation

Curation Rationale

[More Information Needed]

Source Data

Initial Data Collection and Normalization

[More Information Needed]

Who are the source language producers?

[More Information Needed]

Annotations

Annotation process

[More Information Needed]

Who are the annotators?

[More Information Needed]

Personal and Sensitive Information

[More Information Needed]

Considerations for Using the Data

Social Impact of Dataset

[More Information Needed]

Discussion of Biases

[More Information Needed]

Other Known Limitations

[More Information Needed]

Additional Information

Dataset Curators

[More Information Needed]

Licensing Information

[More Information Needed]

Citation Information

{
  author = {Sidali Lamri},
  title = {new LearningQ version for Question generation in transformers},
  year = {2023}
}
@paper{ICWSM18LearningQ,
    author = {Guanliang Chen, Jie Yang, Claudia Hauff and Geert-Jan Houben},
    title = {LearningQ: A Large-scale Dataset for Educational Question Generation},
    conference = {International AAAI Conference on Web and Social Media},
    year = {2018}
}

Contributions

[More Information Needed]

Downloads last month: 35

Edit dataset card

Repository:

GitHub

Paper:

LearningQ: A Large-scale Dataset for Educational Question Generation

Point of Contact:

s.lamri@univ-bouira.dz

Size of downloaded dataset files:

43.5 MB

Size of the auto-converted Parquet files:

57.8 MB

Number of rows:

227,517

context stringlengths 545 71.9k	questionsrc stringlengths 16 10.2k	question stringlengths 11 563
the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .	if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode .	what would a diode look like on a circuit board ?
the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .	so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this .	what is the direction of current in a circuit ( outside of a dc battery ) ?
the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .	and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin .	electron flow vs proton flow ?
the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .	and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here .	why do n't the graphs beyond the moment that there stops being zero current ?
the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .	if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode .	ie what should the graph look like for higher voltages ?
the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .	is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is .	does the current just go to infinity because there is no resistance or something ?
the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .	is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is .	then how does holes constitute hole current ?
the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .	so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire .	how can be voltage in negative ?
the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .	the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes .	why does a photodiode require biasing ?
the diode is our first semi-conductor device , and it 's a really important one . every other semi-conductor is basically made from combinations of diodes . and here 's a picture of a diode that you can buy . this is a , just a small little glass package , and that distance right there is about four millimeters . and inside here , right inside here , is a little silicon chip , and it 's manufactured to be a diode . so the question is , what is a diode ? a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current . one way to understand how a diode works is to draw an iv curve for it . so let 's draw an iv curve for a diode . if it was a perfect diode , made in some unknown technology , what would happen is in the reverse direction , if the voltage across the diode was negative , we 'll label the voltage this way , if the voltage across the diode was negative , that is , this terminal is at a higher voltage than this terminal , there would be zero current flowing . and then for any positive voltage , basically the diode would look like a wire . so i can call that , that 's essentially model number zero of a diode . now when we build real diodes , what happens is we do n't quite get that perfect behavior , so in particular , if we build a diode out of silicon , we can go to a , i 'll go to a number one model . and a silicon diode actually does n't conduct to a slight positive voltage , and then it would go up like that , where this is around point six volts . for a lot of simple circuits that we build , this is a pretty good iv model of a diode . just as a reminder , when we have the iv curve of resistors , a resistors iv curve looks something like this , it was a line that went through zero , and had a constant slope , so a diode is a really different kind of device , it 's a non-linear device , as we can see from this . let me move up here and now we 'll go to a next level model , that is actually the one i wan na talk about most . this is the model of diode that we use most of the time , so i 'll call this model number two . this is the model that you use when you 'll simulate circuits or simulate diodes and we 're gon na talk about this a little bit more . when you have a diode , if i gave you a diode like this , and i said what 's the iv curve of it ? so what i would do is i would find some sort of box that made voltage for me , a power supply , with an adjustment on it , and then i would also have something that read current . so this is an ammeter , and this is a voltage supply . and we hook that up like that . what we 're gon na do is we 're gon na generate this iv curve by making actual measurements of i and v. so my first v setting is zero , that gives me this point here , i hope i measure a current of zero , otherwise this thing would be generating power , which it 's not gon na do . and then i turn up the voltage slightly , and what i notice is there 's no current , there 's no current when it 's at point one volts , or point two volts . and then when it gets to around point six volts , on the diode , here 's vd , and here 's , when the voltage on the diode is around point six volts what i notice is the current goes up . so it goes up to five milliamps , and then a little bit higher , it goes up to ten milliamps , like that , and i can plot out all these points along this part of the curve . now , i go back here and i change the voltage here to read the other way around , and that means i 'm traveling this way on the voltage axis . and what i 'll read , my ammeter , will read zero milliamps . zero , zero , zero , zero , zero . and so they plot in this part of the line here . now if i make this voltage really large and really negative , say i make this like minus 50 volts , that 's this point here , what happens is i see a really sharp increasing current , like that right there , and it keeps going . and that is called the breakdown , vbr is breakdown . and for silicon diodes , minus 50 volts is a typical value for that . this graph here shows a break in the scale , so this is minus one volt , minus two volts , and then we go all the way out to 50 volts , minus 50 volts , and that 's where the breakdown occurs . and most of the time when we 're using diodes , we 're using them between plus or minus one volt across their terminals . that 's how we know what the iv characteristic of a diode is . and what we can do is actually , for this section of the curve right here , for this part of the curve , i can model this with an equation . and the equation looks like this . this is the iv equation for a diode , so this is sort of like the ohm 's law for a diode . i equals is , this is the current , times e to the q , that 's the charge on an electron , times v on the diode , that 's the voltage on the diode , divided by kt minus one . k is boltzmann 's constant , and t is the temperature of the device , measured in kelvin . so this equation actually fits this part of this curve for a real diode , it 's a fitting curve . we 'll look at these constants one at a time . is is called the saturation current . saturation current . and for silicon , for silicon that 's a value of about 10 to the minus 12 amperes , which is one picoampere , that 's how much is is . q is the charge on an electron , and that equals 1.602 times 10 to the minus 19 coulombs . that 's q , vd is the voltage across the diode , k is boltzmann 's constant , that 's a small k , usually , and that equals 1.38 times 10 to the minus 23 joules per kelvin . and the last variable is t , and that 's the temperature , and that 's measured in kelvin , with a big k. kelvin is the absolute temperature scale , so zero kelvin equals minus 273 degrees celsius . very , very cold . so this right here is the diode equation , that 's the diode iv equation . and it has this exponential shape in it , it has this exponential term in it , but when we look over here , maybe this does n't look like an exponential curve , you have n't seen a curve like that . but that actually is just a trick of the scale of this drawing , so what i wan na do now is i 'm gon na zoom in really super close , right on this origin right here , and we 're gon na see how this exponential term shows up , and we 'll see what the meaning of is is . i equals is times e qv over kt minus one , and here 's a close up , here 's an extreme close-up on the origin of the diode curve . the voltage scale is blown up by about a factor of 10 , so here 's 1/10th of a volt forward across the diode , and the current scale is super blown up , this is in picoamperes now , so this is in 10 to the minus 12th amperes instead of 10 to the minus three . and you can see here , this is a more familiar looking exponential curve . and over here there 's a little bit of an offset , there 's a little tiny current in the reverse direction when the voltage is negative . and this amount here , that 's is , flowing in the negative direction in the diode . if we look at the diode equation , and you let v go negative , what happens is this term here in the diode equation becomes very , very small compared to one . and what 's left is is times one , and that 's what we 're looking at right here . this is a really small current , as you can see from the scale here , it 's down in the low picoamps area . almost all the time you can ignore this current , and just treat it as zero . whenever i wan na use a diode in a circuit , and we 'll see how we solve circuits that include these non-linear diodes in them .	a diode is something that conducts current in one direction , and does not conduct current in the other direction . and the symbol we use for a diode looks like this . it has this big arrow here , that points in the direction of the forward current .	is a transistor a diode and if it is could someone help me understand what exactly it does like how does it work ?
have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .	and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body .	isnt the posterior pituitary the one that releases oxytosin and adh ?
have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .	have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self .	what does the synthroid do ?
have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .	in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone .	what is the role of oxytocin in male ?
have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .	and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin .	what types of hormones does the pituitary gland produce ?
have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .	and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea .	is the doctor feeling for my thyroid gland ?
have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .	and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid .	and if so , why would getting a cold cause my thyroid to swell if its primary function is controlling metabolism ?
have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .	and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea .	why is the thyroid gland larger and more protrusive in males ?
have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .	have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self .	which term refers to bulging eyeballs ?
have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .	it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally .	if the hypothalamus secretes paracrine hormones , why is it included in the endocrine system ?
have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .	and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body .	which hormone stimulates the production of thyroid hormone ?
have you ever thought about the way the different parts of our body communicate ? i think we often consider the body to be this one complete thing , this self . but really our body is composed of lots of parts . there are lots of organ systems . and each of those has organs . and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ? well , one way is through the nervous system and through the pre-laid tracks of nerves . but not every part of the body is connected by nerves . i mean how , for example , would part of the brain go about communicating with part of the kidney ? well , to talk about that we 're going to have to talk about the endocrine system . and the endocrine system is a system of organs that are called glands . and these glands secrete little chemical messages that are called hormones . and they release those little chemical messages called hormones into the bloodstream so that they can circulate from one part of the body to another part of the body in order to initiate an effect . and there are many parts of the body that use these hormones to communicate . but certain organs are really defined by this method of communication and we call them endocrine glands . and so one of the major endocrine glands is the hypothalamus . and the hypothalamus is located right here . it 's a member of the forebrain . and as a member of the brain , it receives a lot of those signals that we talked about from the nervous system . so those nerve signals are funnelling into the brain . and the hypothalamus then , as a kind of dual member of the endocrine system , funnels those signals into the pituitary gland . and so because it plays that dual role between the endocrine system and the nervous system , it often gets taglined as the control center of the endocrine system . in addition to stimulating the pituitary gland , the hypothalamus actually make some hormones itself also . and so it makes adh and oxytocin . and adh is antidiuretic hormone . and it 's a main regulator of our fluid volume in our body . and then oxytocin is a hormone that stimulates the uterus to contract for females during pregnancy . and so that 's the hypothalamus , member of the brain and member of the endocrine system where it all begins , the control center . and then right below the hypothalamus is the pituitary gland . and the pituitary gland is located right here , dangling right below . and so the hypothalamus is about the size of a grape . and the pituitary gland is actually about the size of a green pea . but this little green pea is so important that it 's called the master gland . and it 's called the master gland because the pituitary gland takes that stimulation from the hypothalamus and it directs it to all of the other endocrine glands , or at least almost all of the other endocrine glands , such that their function is ultimately dependent on the pituitary gland to work well . and so that little green pea is a really important part of the endocrine system . and so one of the endocrine glands that the pituitary directs is the thyroid gland . and the thyroid gland is located right here in your neck . it wraps around your trachea . and your trachea is your windpipe . and so you can feel this thyroid gland on your neck as you swallow . if you hold your hands right around your adam 's apple and swallow , that meaty thing moving up and down , that 's your thyroid gland . and one of its main jobs is regulating your body 's metabolism . and it does that through the thyroid hormones t3 and t4 . and another name for t3 is triiodothyronine . and another name for t4 is thyroxine . but the thyroid uses these hormones , the thyroid hormones , to stimulate the body 's metabolism , which is crucial because that 's how our body gets energy . and then right behind that thyroid gland are four spots known collectively as the parathyroid . and the main role of the parathyroid is regulating our body 's blood calcium level . and the level of calcium in our blood is hugely important because calcium does a lot of stuff in our bodies . it 's involved in muscle contraction . it 's involved in bone growth . and all of those functions are really sensitive to the level of calcium that 's floating around in our blood . and so the parathyroid glands , those four spots on the back side of our thyroid , regulate calcium through the parathyroid hormone , or pth . and then moving down the torso , we have the adrenal glands . and the adrenal glands are located right on top of the kidneys here . and they 're called the adrenal glands because they 're adjacent to or right next to the kidney system , which is called the renal system in medical speak . but we really need to further divide the adrenal glands into two parts , the outer part and the inner part . so the outer part is the cortex and the inner part is the medulla . and the reason for the distinction is that the inside and the outside of the adrenal glands have two different functions . and so we 'll start with the outside or the cortex . and that 's where the steroids , the adrenal corticosteroids , are made . and two major examples of steroids made in the adrenal cortex are cortisol and aldosterone . and cortisol is one of the body 's stress hormones . so it functions to increase blood sugar in times of stress so we have energy . and it also has some anti-inflammatory functioning . and then aldosterone is one of the major regulating hormones of our body 's blood volume and how much fluid is in our veins and arteries . and so that 's the cortex . and then the medulla makes a class of hormones called catecholamines . and two major examples of catecholamines are epinephrine and norepinephrine . and i 'm going to shorten those as epi and norepi . and sometimes epinephrine is called adrenaline . and that might be a little bit more familiar to you . but these catecholamines are really involved in our body 's fight or flight response , that adrenaline response that we have to a stressful or scary situation . and so the medulla and the cortex make up the adrenal glands . but moving down the list and down the body , we have the gonads . and in females , those are the ovaries , and in males , the testes . and the gonads release the sex hormones . and so in males , the testes produce testosterone . and in females , the ovaries produce estrogen and progesterone . but these sex hormones are mainly involved in the development of our secondary sex characteristics like pubic hair , and larger frames in males , and breasts in women . but they 're also involved in progressing us through those life stages that accompany those sex characteristics , like puberty and menopause . and then last , but not least , we have the pancreas . and it 's located right here in the upper part of the abdomen . and i saved the pancreas for last because it is n't involved as directly with the pituitary glands as the other endocrine hormones were . but it still uses those hormones to stimulate an effect in a different part of the body . and the effect that the pancreas stimulates is control over the blood sugar . and it does that through the hormones insulin and glucagon . and the pancreas is vitally important because without its hormones insulin and glucagon , we ca n't regulate how much sugar is in the body 's blood versus the cells . and that can lead to major diseases like diabetes . and so with the pancreas , we can conclude our list of major endocrine glands . and so as we look at these glands and at these hormones and we think about all of the different effects that are being stimulated in our body by them , it becomes pretty clear that there are n't just a few of these circulating in our bloodstream . there are literally loads of hormones circulating through our vasculature at any given moment . and so that poses a potential problem . if , say , that you 're in the brain and you 're trying to tell something to the kidney , you 're trying to send him a message , and you put that in the bloodstream and you just float it down to him , how do you know that it 's going to get there ? i mean , is n't that what every other endocrine gland is trying to do ? well , it turns out that hormones are a lot like radio waves . in your city or in your town , there are many different radio stations and there are many different songs being played at any given time by those radio stations . and even maybe from the next town over , there are radio waves filling the air of your town . but unless you 're tuned in specifically to that station , you 're not going to pick up on the song that 's being transmitted . and in a very similar way , a hormone is not going to be received unless there 's a very specific receptor on the target cell . and so the receptor and its location are very important in determining the hormone function . and we have classes that we use to help us identify which hormones fall into which function . and so the first class are autocrine hormones . and the autocrine hormones function at the cell that makes them . an example of this is the t-cell in the immune system . it actually secretes a hormone that it makes called an interleukin , that signals the cell itself to increase its effectiveness and its immune function . and then another class of hormones are paracrine hormones . and paracrine hormones function regionally . and an example of that might be the hormones released by the hypothalamus that direct the pituitary gland . and then last , but not least , kind of the classic class of hormones are the endocrine hormones . and these are the hormones that function at a distance . and an example of this might be the pituitary gland stimulating the gonads , way far away . and so we have autocrine , paracrine , and endocrine classes that help us determine how a hormone functions . and so i know i just told you a whole lot about hormones . but this is your introduction into one of the most important ways that the 100 trillion little tiny individual parts of your body communicate .	and all of those organs are made of tissues . and all of those tissues are made of cells . and it 's crazy , but there are 100 trillion -- or at least roughly 100 trillion cells in our body . so it 's curious then how do those 100 trillion different parts communicate ?	how are there trillions of cells in our body ?