Muscarinic Receptors and Drugs (Nursing)

00:00 Hi, welcome to our video on PNS medications.

00:04 Now the official title is muscarinic agonist and antagonist but what I like to call it is "how to avoid death by mushroom".

00:14 We'll get to that in just a minute.

00:16 But first let's do a quick muscarinic receptor review.

00:19 Okay, the receptor subtype is muscarinic.

00:22 This is one of those cholinergic receptor types because it's mediated by acetylcholine.

00:28 And remember we've got them on your eyes, your heart, your lungs, the GI tract, your sweat glands and urinary bladder.

00:35 Now when it says response to receptor stimulation, I want you to write the word, "agonist" above that part.

00:41 That means when an agonist or neurotransmitter like acetylcholine connects with a muscarinic receptor, this is what will happen - Those like in the eye, let's take a look at that It's contraction of the ciliary muscles that focuses the lens for near vision, so you're gonna end up with a contraction of the pupil, or a small pupil.

01:01 The heart rate - it will decrease the heart rate and so on and so on, You can read through those.

01:07 I want you to pause for just a minute and instead of listening to me go through those with you, I want you to read through them and write yourself a quick note out to the side so you can remember what happens when the muscarinic receptor in that location is hit with an agonist like acetylcholine or a drug.

01:28 Okay, now remember muscarinic drugs act like those neurotransmitters.

01:32 So they're either gonna activate or they're gonna block the muscarinic receptor in the peripheral nervous system.

01:38 So a drug can act like a neurotransmitter- it can activate it, that's what a neurotransmitter would do, or it can block it.

01:47 We give those other names.

01:48 "Agonist" is an activator, "antagonist" is a blocker.

01:54 So an agonist is a neurotransmitter.

01:56 For the muscarinic receptors, it will be like acetylcholine or a drug that can bind to the receptor and activate it.

02:04 It will do those things we just talked about in the previous slide, right? the effect on your eyes, what it does to your heart rate - that's what an agonist will do like acetylcholine it hits when it muscarinic receptor on a specific organ.

02:18 Now an antagonist is a blocker.

02:20 You're probably most familiar with an antagonist like a beta-blocker that we use to lower heart rate but we're not talking about the beta receptors, we're talking about thte muscarinic receptors.

02:31 But an antagonist will be a drug that attaches to the muscarinic receptor and bind to that receptor - it won't let anything else in there but it will prevent that receptor from doing what it's intended to do.

02:44 Meaning if we give a muscarinic antagonist, it's gonna connect to those muscarinic receptors and it won't allow that heart rate to go down like it would if an agonist's connected.

02:56 It will bring that heart rate up.

02:58 The exact opposite happens.

03:00 Now this is more interesting than you probably think right now, because this is the "key" to studying these types of drugs.

03:07 Stick wth me and I'l help you understand how this is gonna make your studying much more effective.

03:13 Okay, so muscarinic receptors and drugs.

03:16 I'm gonna talk about how they work together again.

03:18 Now muscarinic receptors are activated it by acetylcholine, right? We start talking about that right from the beginning.

03:25 So look at the muscarinic receptor there on the right-hand side.

03:29 You got an arrow that shows how acetylcholine drops into that and look, the receptor lights up and activates, it does what it's intended to do.

03:38 Now what is intended to do depends on whether receptor is in location Back to that chart where it tells you what will happen if it hits the eye or the heart or the lungs, etcetera.

03:49 So here's where it gets a little tricky because muscarinic drugs are also considered cholinergic drugs.

03:55 Okay, It's really not that tricky but I wanna slow down and make sure it's very clear to you because sometimes we use these terms interchangeably and it feels like, "woah! what are we talking about?" So muscarinic drugs can be considered cholinergic drugs because they mimic acetylcholine.

04:15 Now underline choline in acetylcholine and that will help you remember why we referenced it as cholinergic.

04:23 So muscarinic drugs are cholinergic agonists or they mimic acetylcholine Now anti-muscarinics are also considered anti-cholinergic drugs because they block acetylcholine from activating the receptor.

04:41 Now take a look at our picture, so you've got a big stop sign there.

04:45 There's the receptor.

04:47 You got the anticholinergic drug - that half red circle dropped in there and you can see it's blocking acetylcholine from getting to that receptor.

04:57 That's what antagonist or anti-muscarinic or anti-cholinergic drugs do - they block.

05:06 That's why you have the stop sign to see , "Huh, that receptor is all filled up, it's not going anywhere right now so acetylcholine can't make it to the receptor to activate it."