Epinephrine & Norepinephrine

[tennisboy85]

Hey, I have a quick question. I tried to post in the subforum but it wasn't showing for some reason, so I hope it's ok if I post it here.

Can someone go over Epinephrine and Norepinephrine - their functions and where they are secreted? Are there similarities/differences between them?

For some reason I remember that Adrenal medulla only secreted one of the two, but I was talking with someone who said that it secretes both. So now I'm a bit confused about this topic. Also, I happen to recall that there was a way to convert one form to the other one, but I don't remember what that process is exactly.

If anyone could help me out, that'd be great. Thanks!

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[TRanger]

Epinephrine and Norepinephrine both stimluate the adrenergic receptors of the sympathetic nervous system. The primary difference between the two is what type of adrenergic receptor they stimulate. Alpha 1 receptors are stimulated almost entirely (and may be entirely... might want to check on it) from norepinephrine. Alpha 2 and Beta 1 are pretty much more evenly stimulated by both of them from what I was taught, although I've seen sources that say Alpha 2 is more stimulated by norepinephrine and Beta 2 epinephrine. Finally Beta 2 is mostly stimulated by epinephrine.

BTW Alpha 1 is contracting/excitable. Beta 1 is contracting/excitable and pretty much only found in the heart. The Alpha 2/Beta 2 are both inhibitatory.

The Adrenal Medulla does secrete both, however a far majority of what it secretes is epinephrine. Norepinephrine is secreted by the terminal ends of the sympathetic nerve fibers on the target organ.

Can't tell you anything about changing one into the other though...sorry.

 

[TRanger]

Sorry for the multiple posts...

 

[TRanger]

Sorry for the multiple posts...

 

[TRanger]

Sorry...

 

[TRanger]

Sorry... I wrote the first one during the site maintanence and I didn't realize that it went through and that every single time I refreshed it, another post would appear.

 

[AppleseedCast]

hahah thats awesome. oh and ditto what the above poster said

 

[corbis11]

those two catecholamines are synthesized from the amino acid L-tyrosine. It goes L-tyrosine > L-dopa > dopamine > norepinephrine > epinephrine . I doubt you need to know the enzymes that convert them

 

[Scottish Chap]

Epinephrine and Norepinephrine both stimluate the adrenergic receptors of the sympathetic nervous system. The primary difference between the two is what type of adrenergic receptor they stimulate. Alpha 1 receptors are stimulated almost entirely (and may be entirely... might want to check on it) from norepinephrine

Norepi is actually alpha 1, alpha 2, and beta 1, and epi is all of these plus beta 2. In very low doses, the physiological effect of norepi is mostly from alpha 1 and alpha 2.

tennisboy85: you will not be expected to know every function of the adrenergic receptors and all of the signaling pathways and physiological responses of these receptors for the MCAT - in spite of what the Kaplan book says. This is far too detailed. This is a general exam that requires knowledge of general concepts, so don't worry. If specific, detailed information about receptor pharmacology turns up on the exam (quite possible), they HAVE to give you all the information for understanding and answering the relevant questions in the stem.

 

[Scottish Chap]

ignore

 

[tennisboy85]

Thanks guys. Appreciate the reponses!