The Endocrine System

Hi. It’s Mr. Andersen and welcome
to the Endocrine System podcast. If you look way up there at that guy, his name is Robert
Wadlow and that guy, I have not idea what his name is because he’s not Robert Wadlow.
Robert Wadlow is the tallest man that we have in modern day. He was something like 8 feet
11.5 inches at the time of his death and he was that tall because he was a pituitary giant.
In other words, he had a tumor, we now know, that was pushing on his pituitary. It was
making it produce a hormone called growth hormone which made him get as tall as he eventually
was. And so that wasn’t normal. It does put pressure, and he died young just mostly I
think due to circulation problems. He started to get blood clots. And so basically it talks
a little bit about the endocrine system. When I’m talking about the endocrine system, the
other system that’s really important to talk about is called the nervous system. So the
nervous system remember is basically going to be made up of neurons. So you have all
these dendrites that come into the cell bodies. So the cell body looks like this and then
you have an axon that comes way down here and then you’re going to have another neuron
down here that’s connected with a bunch of dendrites to a cell body and it’s going to
move here. Now this distance right here, or excuse me, the separation between the two
is called a synapsis. A synapsis is going to be a gap between neuron 1 and neuron 2.
Now why is the synapse important? Well, we get control over the chemicals that we send.
But this podcast isn’t about the nervous system and the reason why is that nerves just travel
in one direction, from this neuron to another neuron onto another neuron. They just go in
one direction. And so my analogy is it’s like Gmail. When you send an email from one person
to another person or they send it from one person to another person, that’s like the
nervous system. You’re sending a message from one person with a clear destination and that’s
the nervous system. It goes really fast and it’s going to target a specific cell. And
so when do we use the nervous system? When he have to do something really quick. So if
somebody were to throw something at me and I were to dodge it, that would be my nervous
system that is acting. So the endocrine system is more like Facebook. If I were to post to
my Facebook status update that I am working on a cell communication podcast by myself.
Ironic. And I just put it out there, there’s going to be a delay. There’s going to be time
before other people look at it and dislike it or like it or respond to it. And so that’s
going to be more like the endocrine system. I’m sending it out to everybody and whoever
wants to respond to it can. And so basically keep that in the back of your mind. What are
some terms that you should understand? First of all anything that is going to send out
these messages in the endocrine system is called a gland. And we’ll go over ten important
glands. The chemical that they send out is called a hormone. And then it’s going to target
cells or not. It may target certain cells or it may not target other cells. And so we
could send for example follicular stimulating hormone from the pituitary. It’s only going
to effect the ovaries and the testes, but if we send out growth hormone that’s going
to effect all the cells in your body. So what do those hormones do? They simply diffuse
throughout your body. They’re going to spread throughout your body. And so they are going
to bump into cells or not. They’re going to spread throughout your whole body and that’s
why if you’ve ever felt like adrenaline, you almost get in a car accident, you just feel
like almost something coursing through your body, that’s going to be your endocrine system.
Now when they find cells one of two things can happen. If they are a water soluble hormone,
an example could be epinephrine or adrenaline, they’re water soluble, basically what they’re
going to do is they’re going to dock with a protein on the surface of their cell. Since
they’re water soluble they can’t gain entry to the cell. And so usually what they’ll do
is they’ll set up some kind of signal transduction pathway to have some kind of an action out
here or have another action inside the nucleus where we could make certain specific genes
or certain proteins, transcribe certain genes. But that would be water soluble. We also have
what are called lipid soluble. Testosterone’s an example of that. Basically since it’s lipid
soluble it’s going to move right through that lipid by layer that is the cell membrane and
it also can target with the cell and move right into the nucleus, because again there’s
going to be a lipid by layer here as well. And so lipid soluble hormones are going to
move all the way into the cell. Water soluble are just going to dock with the receptor protein
on the surface. And so here’s our endocrine system. The endocrine system is not as tightly
linked together like the circulatory system, but again it doesn’t have to be because it’s
sending hormones through out the whole body. And so basically we’ve got glands going all
the way up to the top from the pineal gland all the way down to the ovaries and testes
on the bottom. And so basically what I want to do is I’ve chose ten glands in the endocrine
system, ten that I think are pretty important. There are more than that. And then I’ve just
chosen one hormone for each of these and we’re going to talk about that. So let’s talk, let’s
start at the top. The first one is going to be the pineal gland. The pineal gland is right
here. Basically what the pineal gland is going to secrete is a chemical called melatonin.
It does that only when it’s night time. And so if your eyes are open during the day you’re
not going to be secreting melatonin. But when you close your eyes at night, it’s going to
start giving off melatonin. And so basically what that does is that it allows our brain
to tell what time of the day it is and it also allows us to figure out what season it
is. And so basically we can set up what’s called our circadian rhythm. So it’s basically
our internal clock and it’s pineal gland doing that. Next let’s move down here. This part
of our brain is actually called the hypothalamus. And the hypothalamus is kind of the connection
between the brain and the endocrine system. And so it can secrete hormones as well, but
we’re going to say it’s influencing the pituitary. We’re going to talk about what the pituitary
does. Pituitary basically, if we were to look at it like this, the pituitary let me blow
that up a little bit, so the pituitary is going to go down like this and so it’s going
to have two lobes to it. It’s going to have the anterior, anterior means towards the front
or towards the head, and then it’s going to have the posterior. Posterior is going to
be towards your rear end is the best way to think about it. And so what is the anterior
pituitary give off? Well it gives off growth hormone. It gives off a number of other things,
it gives off endorphins, it gives off follicular stimulating, it gives off all these different
hormones, but one that we’re going to talk about is growth hormone. What’s growth hormone
going to do? Growth hormone again is going to float throughout the rest of your body.
It can do that in the circulatory system or through the interstitial fluid and basically
it’s going to cause the cells to grow. So they’re going to get bigger. If we talk about
the next one, anterior, or excuse me, posterior pituitary, it gives off oxytocin but the one
important hormone we are going to talk about is anti-diuretic hormone or ADH. And so anti-diuretic
hormone, well you know what “diure” is, so what is anti-diuretic? Anti-diuretic is going
to be a hormone that holds on to fluids inside our body. Where is that going to go? It’s
going to go to our kidney because our kidney is in control of osmoregulation. What’s the
next one. The next one as we work our way down is going to be the thyroid. So we’re
going to move all the way down here this would be the thyroid gland. It sits right in here.
Basically it does two things that are important. It gives off what are called T3 and T4. Those
hormones and the numbers relate to the number of iodine atoms that are found within it.
And so basically maybe you’ve heard of a goiter, when you get an inflamed thyroid. Basically
what our thyroid does is it regulates metabolism. And so it’s going to give off these two chemicals
T3 and T4 and that’s going to speed up metabolism inside our body. And so if you have a hyperactive
thyroid you have high metabolism. If you have an inactive thyroid then you’re going to have
really slow metabolism. And so basically it’s control of that. And the other thing that
it does is it secretes something called calcitonin. And again endocrine system’s really important
in feedback loops. And so the calcium that we have in our blood, the level that we have
is super important. Especially in nerves and in muscle firing. If we don’t have the correct
amount of blood calcium, we’re going to die. And so basically what the thyroid does, is
that when you secrete the thyroid, it’s going to lower the calcium. Where’s the calcium
going to go? It’s going to go back into the, we’re going to secrete some through the kidneys,
but it’s going to go back into the bones. And so there’s another hormone that kind of
goes with that and so this looks like a butterfly, but there are going to be these tiny little
hormones in here called the parathyroid. They sit right within the thyroid. And their going
to secrete something called parathyroid hormone. What does that do? Well, if the blood calcium
level goes too low, it’s going to raise the blood calcium. And so these two, the thyroid
and the parathyroid are going to work together to basically keep the blood calcium level
correct. It’s the same way that insulin and glucagon work in the pancreas. Speaking of
which, let’s go to the next one. And so the pancreas is kind of hard to see in this diagram.
But the pancreas is going to sit right here, it’s again behind the stomach and it’s going
to empty right here into the duodenum. So it’s going to empty enzymes in here, but it’s
also on its surface it’s got beta and alpha cells that are going to secrete insulin and
glucagon. Insulin is going to be secreted if we ever need to lower the blood sugar and
glucagon if we ever need to raise the blood sugar. So basically what insulin does is when
it’s secreted it allows our cells to take in that blood sugar, that glucose. And glucagon,
when we release that it’s going to release more of that glucose from the glycogen that’s
found right here in the liver. So that’s the pancreas. On the top of our kidneys, so these
would be our kidneys right here, on the top of them we have our adrenal glands. The adrenal
glands have two parts to it. The adrenal cortex is going to be on the outside. The adrenal
cortex is basically what it does is secretes glucocorticoids. And so if you ever have an
injury and you get huge amounts of inflammation in it, they secrete anti-inflammatories. And
so if you’ve ever taken an anti-inflammatory, an example would be like Advil, basically
the glucocorticoids are going to do the same thing. They don’t need to act right away,
and so these are actually connected by hormones to the pituitary so the message can come from
the brain, we have an injury down to the pituitary and eventually to the adrenal cortex. But
that’s not what you’re familiar with in the adrenal gland. You’re familiar with adrenaline.
So there’s a nervous connection from the brain, all the way down here to the center of the
adrenal gland. That’s called the adrenal medulla. Basically what it’s going to have it do, it’s
going to secrete epinephrine. Epinephrine is adrenaline. It’s going to go throughout
your body and it’s going to trigger that fight or flight response. And so again, if you almost
get into a car accident, nervous system is going to allow you to kind of not get in that
car accident, but after that you’re going to feel this adrenaline coursing through your
body. Your metabolism is going to speed up. You’re to suppress like your digestive system.
You’re going to become more alert. And that’s all a result of the adrenal medulla. Next
we’ve got, down at the bottom, we just have the sex hormones and the sex glands. We’ve
go the ovaries, and so this would be in females, and then the testes if we’re talking about
males. Ovaries are going to give off estrogen. Testes are going to give off testosterone
among other things. But basically those are responsible for your female and male sex characteristics.
Now when you go through puberty, before you go through puberty they’re not really cranking
out a lot of estrogen and testosterone. But once you go through puberty, they’re getting
a signal from the pituitary gland that says now it’s time to make these sex hormones and
then we get those secondary sex characteristics. Okay, so how did you do? Can you remember
the ten glands? Can you remember the hormones that they secreted? And what they did? Well,
let’s try. Okay. So as we go through this . . . Testes – Where are they found? They’re
found right down here. What do they do? They give off . . . testosterone, that’s right.
What about the ovaries? Where are they found? Ovaries are going to be found right here.
What do they give off . . . estrogen, that’s right. Sorry for the awkward pauses. It’s
like Dora the Explorer. Next we’ve got the adrenal medulla. Where’s that found? Yeah,
that’s the green. What do they give off . . . that’s right, epinephrine. Let’s got to the next
one, adrenal cortex. Where is that? It’s going to be the yellow part remember around the
adrenal gland. What do they give off? I bet you’ve forgotten this, those are glucocorticoids.
They’re going to be anti-inflammatories. What’s next? That’s going to be the pancreas. Pancreas
is found right here. What’s it give off . . . insulin, glucagon. Those regulate blood sugar. Let’s
go to the next one. It’s the parathyroid. That’s right, that’s going to be within the
thyroid. They used to actually when people get goiters, they cut parts of the thyroid
out and then person would immediately die because they didn’t understand what the parathyroid
did. So a parathyroid is going to be inside here. What’s it going to secrete . . . parathyroid
hormone, that’s right. And that’s going to raise blood calcium. Right above that we’ve
got the thyroid. Thyroid is going to give off two things. Can you remember those . . . It’s
going to give off calcitonin, that’s going to lower blood calcium and it’s also going
to give off T3 and T4. Okay. Let’s go to the next one. Posterior pituitary. So that’s going
to be way up here. What does that give off . . . anti-diuretic hormone. That’s right.
That’s going to keep our body holding on to water, retaining water. And then we’ve got
the anterior pituitary in the front. That gives off a lot of things. Do you remember
what it gives off . . . thinking back to Robert Wadlow . . . right, it gives off growth hormone.
That’s going to cause our cells to grow. And finally we’ve got the pineal gland. Pineal
gland, close your eyes, you’re going to start secreting . . . melatonin, that’s right. And
that allows us to sync up our circadian rhythms. So these are the top 10 glands, top 10 hormones
and I hope that’s all helpful.


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