DrSal

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Hey y'all,

i just wandered over from the MCAT forum b/c i got a Q that's really bugging me.

Is epinephrine a hormone or a neurotransmitter?

It's produced by the adrenal MEDULLA which, according to my physiology book, is modified sympathetic ganglion...yet it's secreted into the blood...

what a horrible question!!!! but please let me know if you know a definitive answer to this Q.

thanks!
 

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DrSal said:
Hey y'all,

Is epinephrine a hormone or a neurotransmitter?
The answer to the question is yes. It fits the standard definition of a nuerotransmitter (made in pre-syn cell. has effect in post syn cell. if released at post cell, will have effect) and also fits the definition of hormone (made in the adrenal medulla, released into blood stream, affects distant sites)

What was the question you had??
 

DrSal

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Well, i got that as an MCAT question, and both hormone and neurotransmitter were answer choices. I picked NT b/c it seemed to fit in better with the passage...

my question is...is there a "real" answer? What were the mcat folks thinking? what are the med students taught?

thanks!
 
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Kalel

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Most people call it a "neuro-hormone", because it really does both. What was the context that the question was being asked in? If forced to choose, I think that I would choose hormone because I think that most NT receptors (in the CNS) that bind to epi are more specific for nor-epinephrine.
 

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I would also say both a neurotransmitter and a hormone. A great example of the conservative nature of biology. One compound to perform multiple jobs.
Like the previous poster said, it depends upon the context of the question. But then is it a trick question? Who knows. It is only one question. If you let this one question bother you now you might have some problems in med school. But anyway, you know the real answer but the answer that the MCAT people want will be as mysterious as the other end of a black hole. Good luck in your search.
 

southerndoc

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It's been a while since I studied neuro, but I thought epinephrine was a hormone only. Norepinephrine, however, was both a hormone and a neurotransmitter.

Am I missing something?
 

KyGrlDr2B

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Just for kicks, I looked this up in stedman's. It says neuro-hormone. This could always be one of those experimental questions that don't even count toward your score. Don't sweat it.
 

southerndoc

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KyGrlDr2B said:
Just for kicks, I looked this up in stedman's. It says neuro-hormone. This could always be one of those experimental questions that don't even count toward your score. Don't sweat it.
OK, enlighten someone who has forgotten his neuro.

Where is epi acting as a neurotransmitter? (Which receptors?) I'm familiar with norepi, but not epi acting in this way.
 

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southerndoc said:
OK, enlighten someone who has forgotten his neuro.

Where is epi acting as a neurotransmitter? (Which receptors?) I'm familiar with norepi, but not epi acting in this way.
beta-adrenergic receptors on cardiac tissue. i think it works the same way as norepi, in that it binds its receptor, upregulating cAMP production, activating PKA,
1) pinning open v-gated L-type Ca2+ channels on the t-tubule membrane
2) increasing calmodulin turnover
3) upregulating ATPase-Ca2+ pumps on sarcoplasm membrane
 

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uclacrewdude said:
beta-adrenergic receptors on cardiac tissue. i think it works the same way as norepi, in that it binds its receptor, upregulating cAMP production, activating PKA,
1) pinning open v-gated L-type Ca2+ channels on the t-tubule membrane
2) increasing calmodulin turnover
3) upregulating ATPase-Ca2+ pumps on sarcoplasm membrane
Yea, I knew the beta- and alpha-adrenergic stimulation, but I didn't consider that a neurotransmitter function as much as a hormone function. By neurotransmitter, I was thinking of things like GABA, glutamate, norepi, histamine, serotonin, etc. in the brain.

I guess technically it could be considered one since it's activating the sympathetic system. I can go for it though.
 
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