Cholinergic and Adrenergic Receptors (Nursing)

00:01 Remember cholinergic receptors are activated by acetylcholine.

00:06 Now, we've got a lot of information here for you about receptors.

00:10 Here's what I want you to keep in mind before we even start this.

00:14 This is the whole key to understanding the peripheral nervous system drugs.

00:20 Okay, first we're gonna look at the cholinergic receptors.

00:24 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.

00:34 Okay, so you're with me? Let's start with the first group, Nicotinic-N.

00:39 Now these are located in all the autonomic nervous system ganglia and the adrenal medulla.

00:45 Okay, so that's where nicotinic-Ns are located.

00:48 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.

01:00 Okay, that's a mouthful.

01:02 But really what happens here, it releases epinephrine from the adrenal medulla.

01:08 Okay, underline that, release epinephrine from the adrenal medulla.

01:12 So nicotinic-N, when it's response, it releases epinephrine from the adrenal medulla, that's the most important point.

01:23 Uh, stimulation of both parasympathetic and sympathetic postganglion nerves and release of epineph- okay, that's a lot.

01:28 So I want you to zero-in on the most important point which is, it releases epinephrine from the adrenal medulla.

01:36 Okay, so there's the first receptor.

01:39 Nicotinic-M is the second receptor subtype.

01:43 Now nicotinic-M is a cholinergic receptor, that means it's mediated by acetylcholine.

01:49 Now these guys work the neuromuscular junction and they help with contraction of skeletal muscle.

01:54 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.

02:03 Now are you ready for the big one? this is muscarinic and you have muscarinic receptors, all kinds of places.

02:11 You have them on your eyes, your heart, the lungs, the GI tract, your sweat glands and your urinary bladder.

02:20 That's a lot of places, so let's kinda walk slowly through that.

02:24 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.

02:32 So when the receptor subtype muscarinic is stimulated, what happens in your eyes is that the ciliary muscles focus the lens for near vision.

02:42 Okay so, it's contraction of the iris sphincter muscle and it causes miosis.

02:47 Now that's a lot to remember, so you might just wanna circle "contraction of the pupil", that's what we're looking for.

02:55 Now in the heart, this is gonna decrease the rate.

02:58 Oh, that should kind of start to be a clue to you, right? this would be more of a parasympathetic response.

03:05 When a muscarinic receptor is stimulated with an agonist, we have more of a parasympathetic response.

03:13 So your lungs, are they gonna need to bronchodilate? Nope, that would be sympathetic.

03:19 So, in this response, you have a constriction of the bronchi, you have increase secretions.

03:25 What about your GI tract? Well, knowing what you know about the parasympathetic response, you would expect right what we have there.

03:35 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.

03:45 Your sweat glands, you might have some generalized sweating and then you're gonna have increased bladder pressure.

03:51 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.

03:59 That's why all those things would slow down in the sympathetic response.

04:04 Muscarinic receptors are the opposite, they're more of a parasympathetic response.

04:10 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.

04:26 Okay, those are three cholinergic receptors subtype functions.

04:32 Now, adrenergic is the opposite system.

04:35 You've got Alpha-1s, Alpha-2s, Beta-1s and we'll talk about the Beta-2s.

04:41 Okay, alpha-1s are located on your eyes, your arteries and veins, your male sex organs, your postate capsule and your bladder.

04:50 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.

05:01 This is that, sympathetic response.

05:04 So, my blood vessels are gonna constrict.

05:06 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.

05:16 That's what happens with alpha-1.

05:18 Now alpha-2, they're in the presynaptic nerve terminals, we're not gonna talk about these a whole lot but they inhibit nerve transmitter releases.

05:25 So alpha-2 is not gonna be our top priority but we just want to introduce you to it.

05:30 Now let's look at beta-1s, they're located on your heart and on your kidneys.

05:36 Now, a little bit later we're gonna talk about beta-2s, those are on your lungs.

05:40 So beta-1s, you have one heart, beta-2s you have two lungs.

05:46 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.

05:56 Now the kidneys, when they're responding, will put out renin.

06:00 Remember what renin does - those kidneys put that out and it's the first step in the RAAS.

06:05 The renin angiotensin aldosterone system which will raise your blood pressure.

06:11 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.

06:23 Now beta-2s are also included in the adrenergic, remember we talked about those, those are located on your lungs.

06:29 But there's a few other places so let's back it up and talk about those.

06:33 Now they're located on the arterioles of the heart, lung and skeletal.

06:37 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.

06:49 But what happens with these when an adrenergic receptor is stimulated, they dilate.

06:56 They dilate because they are getting ready to deliver a lot more blood because they know your body is gonna need it.

07:02 Now the muscles of the bronchi, the uterus, the skeletal, they dilate, relax and increase contraction.

07:08 Let's break that down.

07:10 Now, if i have a beta-2 receptor in my lungs, those muscles will relax and dilate.

07:16 Oh, that makes sense because I'm gonna need a lot more oxygen.

07:20 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.

07:46 Sometimes we use drugs like that to slow labor.

07:50 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.

08:06 Now finally, dopamine.

08:08 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.