Adrenergic VS Cholinergic

[NUNS2016]

Ok...I've been spinning my brain in circles here...one minute I've got it, the next I'm so lost I could die.

Let me see if I have this...at all...and if any or all of this is wrong, please feel free to correct or tweak anything!!

So, within the Autonomic NS, there's the parasympathetic NS and sympathetic NS.

The parasympathetic is the rest and digest.

The sympathetic is fight-or-flight.

Very simply, these two systems are in constant opposition of each other. When one is activated, the other is "off", and vice-versa.

Within the body, there are different types of receptors.

There are adrenergic receptors, for which there are adrenergic agonists (activating the receptor) and adrenergic antagonists (which block the receptor).

There are also cholinergic receptors, for which there are cholinergic agonists (activating the receptor) and anticholinergic (blocking the receptor)

The difference between adrenergic and cholinergic are the fibers by which the "travel"? The ways in which they...act on their receptors? The adrenergic uses the Alpha and Beta receptors. The cholinergic uses AcH.

BUUUUTTTTT:

Whats the reaaaalll difference?? They both work on both para and sympathetic nervous systems, yes?

Is the difference just WHAT they mimic? Which neurotransmitters they mimic??

Even though they can potentially create the same effect...??

For instance...Epinephrine, an adrenergic agonist (?), increases HR, BP, etc., but technically, an anticholinergic does the same thing...but they are different somehow? HOW??!

OR: is it:

Cholinergic agonists increase the "resting and digesting", like lowering HR, lowering BP, increasing GI motility

Cholinergic antagonists decrease the "resting and digesting" (activating SNS??), like raising HR and BP, and decreasing GI motility?

Adrenergic agonists increase "fight-or-flight" and antagonists decrease it?

So if something is a Beta blocker, it "stops" or decreases the SNS thereby decreasing the fight or flight response, lowering HR, BP, etc.?

Ugh, this is all probably gibberish.

HELLPPPPP. Everytime I have it, I spin myself back around. I know its more simple than I'm making it, but this is seriously stalling studying for my patho exam!!!!

Thanks!

[NUNS2016]

And then, what the hell are catecholemines!?!?! My books says "catecholemines produce sympathomimetic responses" and that "noncatecholemines simulate adrenergic receptors"----WTH??!?! So now theres something else that does the same damn thing that I can't figure out already?!

[Esme12, ASN, BSN, RN]

Check out this thread....https://allnurses.com/nursing-student-assistance/please-help-cholinergic-951125.html

[NUNS2016]

OK, so despite what my brain wants me to believe, I think I understand it enough for now, as I study more, it will get better. However, what I'm having trouble with right now seems to be the fact that....some drugs are in one category, but do the same function as a drug in the opposite category? Or is that not true? So I feel like there are lots of drugs that increase the HR, but they're not all Beta 1 agonists, right? So, how are they different and the same?

[MSNce1]

Are you thinking just the opposite or the opposite within that opposite category like

when you spoke of alpha and beta with the sympathetic and parasympathetic within each category. Writing this down in z picture like format will help you a lot:)

[NUNS2016]

I'm not sure I know what you mean. I guess I feel like...there are drugs that are called adrenergic agonists, therefore they "activate" the sympathetic NS, yes?

Then how are there drugs that also deactivate the parasympathetic NS, and are anticholinergics, but aren't adrenergic agonists?

So, what I mean is, an adrenergic agonist and an anticholinergic do, or do not, in fact do the SAME thing?? If something activates the PNS, it therefore deactivates the SNS.......? Or no.?

OR: is it that if the PNS is activated, and the SNS needs activating, it can either do it by blocking the receptors for the PNS (anticholinergics), so the binding to PNS stops, stopping the PNS effects- OR you can choose a drug that actually activates the SNS, by binding with an adrenergic receptor, therefore "deactivating" the PNS..?

[NUNS2016]

So like this…

PNS activated—>block PNS receptor sites (anticholinergic)—>deactivates PNS—>activate SNS

Or you can…

PNS activated—>send adrenergic neurotransmitters to adrenergic sites—>deactivates PNS—>activate SNS

[NUNS2016]

This is some sort of joke! The books says epinephrine act on Alpha 1, Alpha 2, Beta 1 and Beta 2. But, then on the other page, it says that Alpha 1 increases BP and Alpha 2 decreases BP! Uuuuuuuuuugh.

[mrsboots87]

It can be very confusing at first, and I still have a little trouble with it. But some of the things to simplify for you.

Sympathetic nervous system HAS adrenergic receptors. Parasympathetic HAS cholinergic receptors. SO adrenergic and cholinergic are the equivalent of SNS and PNS. There are not adrenergic receptors in the PNS and no cholinergic receptors in the SNS. Also, both systems "run" at the same time. The activation of one, does not necessarily deactivate the other. Just during certain situations the receptors will receive more or less signal.

Also and adrenergic antagonist only blocks adrenergic receptors. It does not activate cholinergic receptors. And adrenergic agonists only increase adrenergic activity, they don't deactivate the cholinergic receptors. Same for cholinergic antagonist/agonist. Neurotransmitters will activate and deactivate each system when signaled to do so by various stimulations. If a tiger is chasing you, your adrenergic receptors will be sent signal to activate and start the fight or flight response. This will not deactivate your cholinergic receptors. It just wont excite them either. Then when you are getting ready to sleep, your cholinergic receptors will get sent the signal to activate, but your adrenergic system will not be shut down. It just wont get excited. If that makes sense.

Then, your drugs are used when you have a disease process that requires whichever receptors to be agonized or antagonized. This does not have affect on both systems. Just one. What I think is confusing you, is that when you antagonize the adrenergic response, it has similar affect to some of the effects of the cholinergic response. But it is not actually sending any signal to the cholinergic receptors. ONLY blocking the adrenergic receptor(s).

This will come with time. Up above, I just how I understand and have simplified the basics. You will find what works best for you.

I would suggest making two charts. One for SNS and one for PNS. Then add in your alpha and beta responses to the SNS and your muscarinic and nicotinic(if you are studying nicotinic) responses to the PNS chart. Then add in your medications and what receptor they affect. This will help keep things a little more organized for simpler learning.

[mrsboots87]

And alpha 2 mostly decreases GI motility. Its effect on BP is not really noteable. Or at least for as much as I have learned. But alpha 2 is also like the black sheep of the SNS in that its effects are not quite in line with the effect of the rest of the alphas and betas.

[mrsboots87]

Also, for a drug example. When you use a beta 2 blocker to reduce BP. Lowering BP is a cholinergic effect. HOWEVER, a beta 2 antagonist is not stimulating any cholinergic receptors. It is merely blocking beta 2 receptors. Since Beta 2 receptors play a large role in increasing BP, by blocking it from receiving any neurotransmitters, BP will drop. There are time when a patient may be prescribed a drug from both the adrenergic and cholinergic antagonist/agonist pool. Because one does not have any affect on the other. But cholinergic drugs have some nasty side effects, so they are generally less common. Hope some of this helps you along.

[NUNS2016]

Awesome awesome. Thank you. You hit the nail on the head with what was confusing me. And you explained it beautifully, and simply. I appreciate you taking the time to see where I was stuck, instead of just running the whole system down for me. I have a book to do that for me! Haha. I have the beginnings of the chart, I will definitely finish it now.

Thank you immensely,

NUNS2016