- [Voiceover] Every hormone in the body is either
categorized as a steroid or a nonsteroid.
Now these steroid hormones are gonna be lipid
soluble, that means they can go right
through the cell membrane.
Really they're pretty close to cholesterol.
While the nonsteroid hormones are really
looking like proteins, and these proteins
are water soluble.
They can not go through the cell membrane.
Now let's do a little more information
on steroid hormones.
Mentioned they're lipid soluble, which means
they go right through the cell membrane.
They're actually made from cholesterol.
That's why they're similar to cholesterol.
They're able to enter right into the target cell.
Once they enter in, they can activate specific
genes to make a protein.
So the hormone itself can actually activate
the gene inside the cell.
Now these are slower than the nonsteroid
because they go through the membrane,
find the right gene, and activate it.
So we're talking minutes to hours for an activation here.
Here we're looking at, that blue up top is
the fluid between two cells.
The top part says capillary, that's the blood.
So the hormone, in this case the steroid-based
hormone, can come through blood and get into
the interstitial fluid, the fluid
between the cell and capillary.
It can then diffuse right through the cell membrane.
That's because the steroid hormones are lipid soluble.
Well it goes in, eventually activates a gene,
but activating a gene is gonna start protein synthesis.
With protein synthesis, you make a new protein.
That new protein can alter that cell's activity,
it could be transported to another cell,
but there's some reason why the body triggered
the production of this protein.
It's really four steps here: hormone diffuses
through membrane, hormone activates the gene,
which then triggers protein synthesis,
and the protein then will change this cell
or some other cell's activity or even be
a structural, help to build something.
The nonsteroid hormones, well, remember
they're water soluble.
That means they cannot go through the cell membrane.
And since they can't go through the cell
membrane, they must bind to receptors
on top of the cell membrane.
So the nonsteroid hormones will stay outside
the cell but bind to an external receptor.
Once they bind to this external receptor,
they then go through pretty much this intermediate
mechanism, referred to as a secondary messenger.
So it takes the message from the hormone,
which is outside the cell, that message is
translated to the internal mechanism,
and that internal mechanism carries it along.
This is usually the faster method because those
internal mechanisms have very specific processes.
So here we go.
This is gonna be your nonsteroid hormone.
Same basic stuff, the blood capillary's up top,
interstitial fluid's the middle, then you see
the target cell membrane is a double-faced
lipid dilator.
We can notice that the receptors now
are facing outside the cell.
So the hormone binds to the receptor.
The receptor, then, can go through and activate
a secondary messenger because the primary
messenger or first messenger was the actual hormone.
The hormone couldn't come in so it's transferred
its information to a secondary messenger.
That secondary messenger could then activate
an enzyme which might activate another enzyme
which might activate another enzyme,
and eventually the final product is there.
So you might have three different enzymes,
you might have two, you might have five.
It's not an exact always three enzymes.
Depends on the cycle.
The important part here is they're using
a secondary messenger.
The hormone never came in.
Now these hormones, those may physically be
a steroid-based or nonsteroid-based, whether it's
lipid soluble or water soluble.
A large amount of these hormones are dealing
with homeostatic control of the mechanisms
in your body.
They're helping to keep them working,
helping to keep them safe, and making sure
everything runs like clockwork.
Next is where these negative feedback
loops come in.
In the case of the endocrine, the endocrine gland
can be the control center, can send information
out, in this case sending the hormones out,
and get information back.
The hormones travel from the endocrine gland,
control center, and then travel to the effector,
whatever is going to make a change.
The target tissues or organs, whatever is making
that change, that is the effector.
Once an action has been performed, it'll then
send information back to the endocrine glands.
But it will be in communication the entire time.
There's always a little bit of feedback
bouncing back, saying "we need more hormone,"
"we need less hormone."
So helping to control the amounts of hormone.
You can pretty much think of a negative feedback
loop as a self-correcting loop.
If something's going wrong, you send back
the negative information.
The control center fixes it, sends it back
forward, hopefully it's right this time.
So negative feedback loops are trying
to correct problems.
Here we have a basic idea of what we're looking at.
Controlled variable, very simplistic.
If that particular variable ends up being too low,
the entering gland or control center
will get that information.
It could then send a hormone to a target cell,
target tissues, whatever's not working properly,
which then, once the hormone's there, it can
reverse it and go back up to proper set point.
So the endocrine glands can tell us about
what is going on in the body, send hormones out
to correct what's wrong.