Review: Cholinergic Receptors and Anticholinergic Medications (Nursing)

by Rhonda Lawes, PhD, RN

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    00:00 Now let's talk about cholinergic receptors. Now, in order to be a cholinergic receptor, we've talked in other videos but just in case you haven't caught those, let's go back over it one more time as a review. Now cholinergic receptors are activated by acetylcholine. So you see we've bolded the letters there in choline, underline the letters choline and the receptors. That will help you just kind of review that again. Now, muscarinic and nicotinic receptors are activated by acetylcholine. That's why we call them cholinergic receptors. Remember, adrenergic receptors are activated by...Right, norepinephrine and epinephrine. And we hit those beta-2 adrenergic receptors when we need to rescue the patient who is in trouble. Cholinergic receptors are activated by acetylcholine. So the muscarinic and nicotinic receptors are activated by acetylcholine that's why they're called cholinergic. So in healthy lungs when everything is in balance, muscarinic receptors control smooth muscle tone, mucus secretion, vasodilation, and inflammation. Okay, whew. They do a lot of things. Under normal circumstances, this is good. Muscarinic receptors, they control the smooth muscle tone so you do need some muscle tone, your mucus can play a role, a vasodilation is appropriate and inflammation as needed. Well, hey now we're starting to get into some problems. Right? Because if there's so much of this going on in the lungs we're going to need to block some of that. Because what if we have more smooth muscle tone constriction than we wanted? What if you have more mucus than you need? What about this vasodilation and inflammation? That all leads to airways that are difficult to breathe through. Because we think of examples COPD and asthma, the muscarinic receptors are the ones that contribute to increased bronchoconstriction. Okay, so the muscarinic receptors when they're hit with acetylcholine and remember that can be made by the parasympathetic nerves, that can be made from the epithelial lining cells. So there is a lot of it available to the patient. If the patient has COPD or asthma, they have this problem with bronchoconstriction and mucus secretion that narrow the airways. So look at our graphic. You've got a normal airway at the top then we've got an inflamed airway that you might see in COPD or asthma. See this muscarinic receptors are hit with acetylcholine and they're going crazy. They're making extra bronchoconstriction. They're making extra mucus than you would normally see in a normal airway. That's why patients with COPD and with asthma have a difficult time breathing. Because they airways are actually smaller and filled with thick mucus. So, how does an anticholinergic medication work? Well, look you still got choline in there. Right? That's cool so we know that acetylcholine is involved, but the word anti means against. So this is against acetylcholine. Oh, that's what anticholinergics do. So, anticholinergic medications, they're bronchodilators because they block those cholinergic receptors. Well I know when a cholinergic receptor, like the muscarinic ones in the respiratory system are activated, when they come they connect and bond to acetylcholine, what happens? Bronchoconstriction? Mucus production? So you give me an anticholinergic medication, that's a medication that mimics acetylcholine. So it will attach to a cholinergic receptor, the muscarinic ones, in the airway. Now, it won't let acetylcholine attach to that receptor.

    04:01 So even when the body puts out acetylcholine, you've got less receptors available. An acetylcholine and a muscarinic receptor have to connect in order to have that bronchoconstriction and excess mucus. So if I've got a cholinergic receptor and I've got an anticholinergic medication bound to that, when acetylcholine comes swimming by, there's nothing it can do.

    04:26 Right? It can't get to that receptor because the medication is already bound to that receptor.

    04:31 So you have less bronchoconstriction and mucus production. That's why an anticholinergic is considered a bronchodilator. Because it's blocking the action of muscarinic receptors in the respiratory tract. So, anticholinergic are bronchodilators because there's less bronchoconstriction, you also will have probably less mucus because they bind to those muscarinic receptors, they block the action of what they would normally do if acetylcholine had got there. Hence the name, anticholinergic medications. Okay so let's look at some of these. They block acetylcholine from binding to the muscarinic receptors, you already got that. Cholinergic reflexes is bronchoconstriction, it's blocked. Now, the muscle bands around the airways are blocked from tightening and clamping down in a quick way. So some example drugs like ipratropium bromide, so you'll see this used also as a rescue inhaler. That's why an anticholinergic medication can help the patient who's in breathing distress. Now, you heard me go on about that. I want you to pause a video and answer a couple questions in your notes. Here's the questions I want you to consider. What makes a SABA a SABA? What receptors are involved? How quickly does a SABA act? What makes an anticholinergic medication, anticholinergic? Which receptors are involved? Isn't anticholinergic an agonist or an antagonist? Okay, which one I use in an emergency? A SABA or a LABA? Okay, spend some time with those questions.

    About the Lecture

    The lecture Review: Cholinergic Receptors and Anticholinergic Medications (Nursing) by Rhonda Lawes, PhD, RN is from the course Obstructive Respiratory Disorders (Nursing).

    Included Quiz Questions

    1. Acetylcholine
    2. Epinephrine
    3. Norepinephrine
    4. Short-acting 2 beta-agonists
    1. Smooth muscle tone
    2. Mucus secretion
    3. Inflammation
    4. Gas exchange
    5. Vasodilation
    1. Chronic obstructive pulmonary disease (COPD)
    2. Asthma
    3. Persistent dry hacking cough
    4. Respiratory syncytial virus (RSV)
    5. Influenza

    Author of lecture Review: Cholinergic Receptors and Anticholinergic Medications (Nursing)

     Rhonda Lawes, PhD, RN

    Rhonda Lawes, PhD, RN

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