Remember cholinergic receptors
are activated by acetylcholine.
Now, we've got a lot of information
here for you about receptors.
Here's what I want you to keep in
mind before we even start this.
This is the whole key to understanding
the peripheral nervous system drugs.
Okay, first we're gonna look
at the cholinergic receptors.
If you know the name of the receptor we
call the subtype, where it's located
and then what happens when that receptor is
stimulated, that means an agonist went on it.
Okay, so you're with me?
Let's start with the first
Now these are located in all the autonomic
nervous system ganglia and the adrenal medulla.
Okay, so that's where
nicotinic-Ns are located.
Now when these receptors, the nicotinic-N
are hit when they're mediated,
their response is stimulation of both the parasympathetic
and the sympathetic postganglion nerves.
Okay, that's a mouthful.
But really what happens here, it releases
epinephrine from the adrenal medulla.
Okay, underline that, release
epinephrine from the adrenal medulla.
So nicotinic-N, when it's response, it
releases epinephrine from the adrenal medulla,
that's the most important point.
Uh, stimulation of both parasympathetic and sympathetic
postganglion nerves and release of epineph-
okay, that's a lot.
So I want you to zero-in on
the most important point which is,
it releases epinephrine
from the adrenal medulla.
Okay, so there's the
Nicotinic-M is the
second receptor subtype.
Now nicotinic-M is a cholinergic receptor,
that means it's mediated by acetylcholine.
Now these guys work the neuromuscular junction and
they help with contraction of skeletal muscle.
Alright, so we've got N, which gives us
epinephrine from the adrenal medulla,
we've got nicotinic-M that causes
contraction of the skeletal muscle.
Now are you ready
for the big one?
this is muscarinic and you have muscarinic
receptors, all kinds of places.
You have them on your eyes, your heart, the lungs, the
GI tract, your sweat glands and your urinary bladder.
That's a lot of places, so let's
kinda walk slowly through that.
We eased you into it that nicotinics
that aren't very many places
and then we introduce you to
muscarinic which is all those places.
So when the receptor subtype muscarinic is
stimulated, what happens in your eyes is that
the ciliary muscles focus
the lens for near vision.
Okay so, it's contraction of the iris
sphincter muscle and it causes miosis.
Now that's a lot to remember, so you might
just wanna circle "contraction of the pupil",
that's what we're looking for.
Now in the heart, this is
gonna decrease the rate.
Oh, that should kind of start to be a clue to you,
right? this would be more of a parasympathetic response.
When a muscarinic receptor is stimulated with an
agonist, we have more of a parasympathetic response.
So your lungs, are they gonna
need to bronchodilate?
Nope, that would be sympathetic.
So, in this response, you have a constriction
of the bronchi, you have increase secretions.
What about your GI tract?
Well, knowing what you know about
the parasympathetic response,
you would expect right
what we have there.
You're gonna have increased saliva, increased gastric
secretions, increased intestinal tone and mobility
because I'm getting ready
to eat a big, fat, meal.
Your sweat glands, you might
have some generalized sweating
and then you're gonna have
increased bladder pressure.
Now remember, if I'm in
a sympathetic response,
I'm getting ready to run, so I don't have
that time to stop and eat or to pee.
That's why all those things would slow
down in the sympathetic response.
Muscarinic receptors are the opposite,
they're more of a parasympathetic response.
That's why, my heart rate is slower, my lungs are not needing
to bronchodilate, my GI tract is getting ready to eat,
I'm a little sweaty and I have
increased bladder pressure
because I'm getting ready and I have all
the time I need to to take a potty break.
Okay, those are three cholinergic
receptors subtype functions.
Now, adrenergic is
the opposite system.
You've got Alpha-1s, Alpha-2s, Beta-1s
and we'll talk about the Beta-2s.
Okay, alpha-1s are located on your
eyes, your arteries and veins,
your male sex organs, your postate
capsule and your bladder.
Okay, now we're gonna expect kind
of opposite responses here, right?
So these pupils are going to dilate, arteries
and veins are gonna constrict, right?
because it's gonna try and shunt
all the blood to where I need it.
This is that,
So, my blood vessels are gonna constrict.
This is also what allows males to have an
ejaculation, the prostate capsule will contract
and the bladder and sphincter are gonna
contract because we don't have time to pee.
That's what happens
Now alpha-2, they're in the presynaptic nerve
terminals, we're not gonna talk about these a whole lot
but they inhibit nerve
So alpha-2 is not gonna be our top priority
but we just want to introduce you to it.
Now let's look at beta-1s, they're located
on your heart and on your kidneys.
Now, a little bit later we're gonna talk
about beta-2s, those are on your lungs.
So beta-1s, you have one heart,
beta-2s you have two lungs.
So beta-1 is located on your heart and your
kidneys because I need my heart to step it up,
my heart rate is gonna increase and
it's gonna pump faster and harder.
Now the kidneys, when they're
responding, will put out renin.
Remember what renin does - those kidneys put
that out and it's the first step in the rest.
The renin angiotensin aldosterone system
which will raise your blood pressure.
So when beta-1s are stimulated, the heart and
the kidneys respond by increasing the rate,
the force of the heart contracts
and the kidneys put out renin.
Now beta-2s are also included in the adrenergic, remember
we talked about those, those are located on your lungs.
But there's a few other places so let's
back it up and talk about those.
Now they're located on the arterioles
of the heart, lung and skeletal.
Okay, why that's an issue is because your
arterioles are little tiny branches of the arteries
and when those guys are vasoconstricted,
holy cow! that would really ramp things up.
But what happens with these when an adrenergic
receptor is stimulated, they dilate.
They dilate because they are getting ready to deliver a lot
more blood because they know your body is gonna need it.
Now the muscles of the bronchi, the uterus, the
skeletal, they dilate, relax and increase contraction.
Let's break that down.
Now, if i have a beta-2 receptor in my
lungs, those muscles will relax and dilate.
Oh, that makes sense because I'm
gonna need a lot more oxygen.
But what are you talking about my uterus
for? I mean, why is my uterus gonna relax?
Well, just picture this, if I was getting ready
to run, I don't have time to drop a kid, right?
So, I don't want a uterus that pushes a kid out, I want it to
relax and so that's how you can remember why the uterus relaxes
because in a sympathetic response or in an adrenergic
receptor is stimulated, the uterus will relax.
Sometimes we use drugs
like that to slow labor.
Now skeletal, we want increased contraction
because I'm getting ready to, you know, run!
Now the liver, this is the glycogenolysis that
just says my liver is gonna make energy for me,
it's gonna release that stored
energy so I can use it for running.
Now finally, dopamine.
That's a type of receptor,
it's located in the kidneys
and that will just cause dilation of the kidney
vasculature so it gets more blood flow to it.