[B]Catecholamine neurotransmitters[/B]

[websie]

Hello people,
Can anyone help me answering this question: adrenaline and noradrenaline are synthesised in and released from the medulla of the adrenal glands into the blood stream. These chemicals also act as neurotransmitters released by sympathetic nerves. Where I get stuck is when it comes to how NA and Adrenaline get into the nerve fibres from the blood (assuming of course, that this is how it works).

Thanks a lot for your help.

websie

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[DrTacoElf]

Total guess but I would think they simply cross the blood brain barrier and enter the nervous system there..

 

[Ankylosed]

Total guess but I would think they simply cross the blood brain barrier and enter the nervous system there..

Catecholamines for endocrine function are synthesized in the medulla of the adrenal, but for neuro function they are synthesized in the soma of the particular nerve and dragged down the axon by microtubules. Anyone else concur?

 

[websie]

Catecholamines for endocrine function are synthesized in the medulla of the adrenal, but for neuro function they are synthesized in the soma of the particular nerve and dragged down the axon by microtubules. Anyone else concur?

That means there are two different sites for the synthesis of catecholamines then? If that's the case, can anyone explain what the advantage is in having two different sites of synthesis and modes of diffusion?

Thanks.

W

 

[TucsonDDS]

Catecholamines for endocrine function are synthesized in the medulla of the adrenal, but for neuro function they are synthesized in the soma of the particular nerve and dragged down the axon by microtubules. Anyone else concur?

I concur, sounds right to me. Also remember that the medulla is very similar to nervous tissues in a lot of ways. It is derived from Ectoderm, just like the CNS. It also recieves its sympathetic stimulation directly from preganglionic fibers. This is the only place in the body (that I can think of right now) that doesn't recieve sympathetics from post ganglionic fibers. Our instuctor told us that the medulla is closer related to nervous tissue than any other tissue in the body so it would make sense that it secretes hormones that are used in the nervous system. Also the hormones that it is secreting provides for the sympathetic response; vasoconstriction in the extremities and GI, vasodilation to muscles, eyes and brain, etc.

 

[Lolita]

I agree. The chromaffin cells in the adrenal medulla are derived from neural crest cells and are the site of postganglionic synapse for sympathetic fibers releasing norepinephrine and epi.

 

[darius99]

yup, there are 2 functions: endocrine and neurotransmitter.
adrenal medulla makes them for release to the bloodstream (think of epinephrine and its effects to mobilize glucose in a manner similar to glucagon), and then the appropriate neurons synthesize them for release as neurotransmitters

 

[websie]

KxM99,
thanks for making this clearer. I was getting confused because I believed the same epinephrine and norepinephrine that are used as endocrine substances as well as being released by sympathetic nerves were synthesised by the medulla. It did not occur to me that neurons would synthesise their own epinephrine and norepinephrine.

This leads me to another question: what are the key differences between E and NE - apart from their formula, of course - both as endocrine and neurotransmitter substances?

Thanks again for your help.

Websie

 

[darius99]

well for one, epinephrine is secreted only by the adrenal medulla, but norepinepherine is secreted by the adrenal medulla and the postganglionic neurons of the sympathetic nervous system (i don't think i made that clear in my first post).
in terms of effects, they are very similar, but they have different receptors. Epinephrine binds to Beta-receptors in the heart (increased heart rate) and smooth muscle in the bronchioles (bronchodilation). Norepinephrine binds to Alpha-receptors in the arterioles. this means that norepinephrine causes decreased blood flow to the skin, gut, and some other organs, so that there is more efficient flow to the heart. i am not positive but i think epinephrine causes increased blood flow to the muscles as well.

 

[pharmacology]

All neurotransmitters are synthesized in the nerve be it NE or 5HT. For NE, tyrosine is absorbed into the nerve just like other nutrients and converted into dopamine and/or NE. There is a specific regulatory step in the synthesis pathway that is the rate-limiting step and important with respect to therapeutic use of drugs such at L-dopa or pathway inhibitors.

 

[websie]

Thanks to everyone who answered my questions. Thanks to you I now feel more confident about catecholamines.

Take care.

Websie

 

[ItsGavinC]

SDN at its finest right here. Good thread guys!