Review of Acetylcholine and Muscarinic Receptors (Nursing)

by Rhonda Lawes

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    00:00 Okay so we’re back to that word, what activates cholinergic activity in the lungs? Well, remember which part we asked you to circle - choline, right?p So what activates the cholinergic activity in the lungs? Yep, there's the answer - acetylcholine.

    00:20 so that's what makes it cholinergic activity, it's because acetylcholine is the agonist, That's the main ones that makes things happen.

    00:29 So acetylcholine is the substance that makes cholinergic activity happen.

    00:35 So acetylcholine activate cholinergic and muscarinic receptors in the lungs.

    00:43 Okay, I threw you a curveball, right? I'll put another one in there.

    00:46 Really I promise, it's straight forward.

    00:48 Acetylcholine is the substance or an agonist.

    00:53 Remember an agonist makes things happen, right? It makes those receptors do what they're fired to do.

    00:59 An antagonist will bind to the receptor and block the action but acetylcholine occurs in your body and it is the substance that activates both cholinergic and muscarinic receptors in the lungs.

    01:15 Now I'm going over that slowly because it's important that you get it and sometimes information comes at you so fast, it's hard to process it.

    01:23 So what makes a receptor cholinergic? is if it is fired up or activated or by acetylcholine, that's why we call it cholinergic Now two types of receptors that are cholinergic or activated by acetylcholine are cholinergic - that one's easy! and muscarinic receptors.

    01:46 That one's a little harder to remember but since we've make sure you make a special note of it so it will make sense as we continue moving through the rest of the section Okay, so when the muscarinic receptors - you might want to write that, muscarinic receptors right above it, acetylcholine activates so when the muscarinic receptors on the airway smooth muscle are activated, the smooth muscle will cause bronchoconstriction.

    02:12 Yes! all the work you just put in with me from the beginning part of this pays off here, so your brain already knows, like oh, pffft this is easy.

    02:21 Smooth muscle, I know where that is, that's in the walls of the airway, that's around the airways, so when these muscarinic receptors are hit with acetylcholine, they're activated.

    02:34 What's the job of a muscarinic receptor in the airway?p Well it's to makebronchoconstriction happen by constricting the smooth muscle.

    02:44 Now we already know that smooth muscle is all over the body, right, in the hollow organs but we're focusing in on this video right on airway.

    02:54 So cholinergic activity in the lungs, two types of receptors, they're cholinergic receptors and muscarinic receptors.

    03:03 Did you get that name? because they're activated by acetylcholine.

    03:08 So when the muscarinic receptors in the airway smooth muscle activated, that's when they cause broncoconstriction meaning, "I can't breathe very well".

    03:22 Okay, so muscarinic receptors, we got two types, there's muscarinic receptors and nicotinic receptors.

    03:29 Okay,woah! she's going rogue now, no no no - I promise just stay with me.

    03:34 So these cholinergic receptors that bind to acetylcholine, we've got muscarinic and nicotinic.

    03:40 Now in healthy lungs, muscarinic receptors, said that one wrong, didn't I? In your healthy lungs, muscarinic receptors control smooth muscle tone, right? They also control mucus secretion, vasodilation, and inflammation See it's really important that I slow down there because I'm adding another layer to your understanding.

    04:05 So you already know muscarinic receptors are activated by acetylcholine.

    04:12 In healthy lungs, muscarinic receptors control smooth muscle tone.

    04:16 Yeah, yeah, yeah - we already knew that part.

    04:20 Okay, but they also do vasoconstriction, vasodilation and inflammation.

    04:26 Okay cool, so that makes sense that's why when we look at those airways when they are all swollen, that's because, look it's vasodilating.

    04:39 That makes those tissues all swollen so the vasodilation, and then it fills up with the gunk - that's the mucus secretion.

    04:48 so that makes sense why when those muscarinic receptors are activated and the normal control - you have the smooth muscle control, the muscle tone right, the mucus being secreted, vasodilation and inflammation.

    05:03 When it is out of control, now its the airway you look at that, it was all really too much of, and gunk and tightening down of the muscles.

    05:14 So in chronic obstructive pulmonary dosease and asthma, the cholinergic mechanisms are the ones,they're responsible for making the increased bronchoconstriction and mucus secretions that's why it's hard to breathe.

    05:31 Okay, one more time from the top as they say.

    05:34 Okay so we've got muscarinic receptors, we're focusing in on the muscarinic receptors that are activated by acetylcholine in your lungs right now, hopefully, you're not sick.

    05:44 But in healthy lungs, muscarinic receptors do things that are good, they control smooth muscle tone, they control mucus secretion, vasodilation and inflammation.

    05:55 When it's out of control in one of these diseases like asthma or COPD, those same things are not in the approppriate balance.

    06:03 So, just like we talked about, you've got muscle tone that clamped down, you've got extra mucus, think of it like trying to walk through Jell-O, you've got extra vasodilation so those tissues are really really swollen and you've got inflammation.

    06:22 Now I want to hit that vasodilation point again.

    06:25 Remember, have you ever like a, you got a cold and you can't breath in your nose, you're like "I can't breathe, I hate this. You can't eat, can't sleep cause you can't breathe, if I could just blow my nose, if I could just blow my nose one time really good, I know I could breathe".

    06:43 You blow, you blow, you blow nothing comes out - what's the problem? Well it's not mucus It's because those tissues are vasodilated and they're all swollen and that's what made your nasal passages smaller Same thing happens in your airways, those passages gets swollen from that vasodilation, that's another reason why you can't breathe.

    07:06 Okay, we've hung out a lot of time here, talking about mucus and swollen because I want you to have a crystal clear picture of what goes on in these airways and what it feels like to be that patient.

    07:21 So now you know that this is an airway out of control.

    07:24 The normal things that happen in your airway are now happening in an exaggerated extent and that's why it's so difficult to breathe.

    07:32 So back to our friend acetylcholine, remember that's the one that activates muscarinic receptors.

    07:38 So you got these parasympathetic nerves, they're the ones that synthesize or they make and release acetylcholine so were you're wondering where this stuff came from? Now you know.

    07:48 Acetylcholine is synthesized and released by the parasympathetic nerves, okay? They're the primary source of acetylcholine in the lungs.

    07:58 Okay, check! That's important that you remember.

    08:02 Where does this stuff come from? Remember acetylcholine is not bad it's just in these disease processes, it's out of control, alright? We got too much of it.

    08:13 So where does acetylcholine come from? Wow, she repeats herself a lot.

    08:18 Exactly, because I want you to do well on your exams and to be an excellent nurse.

    08:23 So where does acetylcholine come from? We know the parasympathetic nerves synthesize and release acetylcholine.

    08:32 Okay good, you got the first point.

    08:35 So acetylcholine can also be synthesized and released by the epithelial and endothelial cells in the lungs.

    08:43 Holy cow, you're like an acetylcholine factory.

    08:48 So not only do the prasympathetic nerves do it, also the epithelial and endothelial cells can do it.

    08:56 Wow, that's the potential for quite a bit of acetylcholine.

    09:01 Remember that that acetylcholine, we bolded that for you, acts directly at the muscarinic receptors on the airway smooth muscle that's what causes the bronchoconstriction and the mucus secretion in the airways.

    09:16 So anticholinergics, here's the rescue.

    09:21 Look at that word, anti- always means against, right? Anticholinergics are medications, so they're against that acetylcholine.

    09:33 Remember we talked about agonist, activator receptor.

    09:36 Anticholinergics are antagonists.

    09:40 They block the effects of acetylcholine from the muscarinic receptors.

    09:45 So those anticholinergics go racing, in they connect to the muscarinic receptors and you remember what the muscarinic receptor's job is right? It causes that smooth muscle constriction and mucus secretion.

    09:59 But if I have an anticholinergic medication there at the receptor, acetylcholine might get produced but it's all dressed up with no place to go because the receptors' dance card is already full.

    10:13 Right, the anticholinergic is on that cholinergic receptor, on that muscarinic receptor and so it takes acetylcholine connecting with the receptor in order for that smooth muscle to constrict, and the mucus to be created, got it? We have a winner.

    10:30 So now you know where acetylcholine comes from, two places, acetylcholine comes from two places: the parasympathetic nerves and it also comes from the epithelial and the endothelial cells in the nerves.

    10:44 Now what we can do to try to fix it is we can give you an anti against cholinergic so an anticholinergic will block acetylcholine's access to that receptor and make all that happen.

    10:58 So if I'm someone who has problems with my airways being inflamed and making extra mucus, if I take an anticholinergic, my airways are gonna be less constricted, right? because that smooth muscle's not going to clamp down as much and I'm not gonna have as much mucus produced as if I hadn't taken an anticholinergic medication.

    11:20 There you go, you've done great walking with me through that.

    About the Lecture

    The lecture Review of Acetylcholine and Muscarinic Receptors (Nursing) by Rhonda Lawes is from the course Lung Disorders (Nursing).

    Included Quiz Questions

    1. Acetylcholine agonist
    2. Norepinephrine antagonist
    3. Epinephrine agonist
    4. Acetylcholine antagonist
    1. Bronchospasm
    2. Inflammatory response
    3. Allergic reaction
    4. Relaxation of the smooth muscle
    1. Cholinergic receptors, specifically muscarinic
    2. Adrenergic receptors, specifically muscarinic
    3. Cholinergic receptors, specifically nicotinic
    4. Adrenergic receptors, specifically nicotinic
    1. Control smooth muscle tone
    2. Control mucus secretion
    3. Control vasodilation
    4. Control inflammation
    5. Control skeletal muscle tone
    1. Parasympathetic nerves
    2. Epithelial cells in the lungs
    3. Endothelial cells in the lungs
    4. Squamous cells in the smooth muscle
    5. Phrenic nerve
    1. Anticholinergics
    2. Analgesics
    3. NSAIDs
    4. Antibiotics

    Author of lecture Review of Acetylcholine and Muscarinic Receptors (Nursing)

     Rhonda Lawes

    Rhonda Lawes

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