The sympathetic cholinergic system dilates thermoregulatory vessels in the
skin. Blushing I believe is also sympathetic cholinergic (probably the same
vessels are involved in both). Since beta 2 receptors are much more
responsive to Epi than to NE, coronary vessels and bronchioles dilate in
response to stimulation by Epi. The outer coronary vessels contain alpha
receptors and will constrict in response to binding NE. The myocardial
vessels have beta 2 receptors and dilate in response to binding Epi.
Excessive NE release (due to stress, anxiety, etc.) can cause angina due to
the vasoconstriction. Now these vessels are also subject to local metabolic
controls. An increase in tissue CO2 or decrease in O2 can override the
nervous system effects.
Dayton J. Ford, Ph.D.
Associate Professor of Biological Sciences
St. Louis College of Pharmacy
4588 Parkview Place
St. Louis, MO 63110
dford@xxxxxxxxxx
314-446-8463 voice
314-446-8460 FAX
-----Original Message-----
From: HAPS-L-owner@xxxxxxxxxxx [mailto:HAPS-L-owner@xxxxxxxxxxx] On Behalf
Of Donna White
Sent: Tuesday, March 07, 2006 9:45 AM
To: HAPS-L@xxxxxxxxxxx
Subject: RE: [HAPS-L] Norepi effects on beta receptors
I thought that vasodilation, at least peripherally, was mediated by
cholinergic sympathetic postganglionic fibers activating muscarinic
receptors in blood vessels. Please please please correct me if I am
wrong.
Donna White
Professor of Biology
Marketing Manager, Human Anatomy and Physiology Society
972-881-5889 phone
972-881-5619 fax
>>> mweck@xxxxxxxxxx 03/06/06 6:36 PM >>>
"Andere Lander, andere Sitten" Different countries different customs,
or in this case different tissues, different receptors. I was always
under the impression that vasodilation was mediated by beta receptor
activation and vasoconstriction was mediated by alpha receptor
activation.
Margaret Weck
________________________________
From: HAPS-L-owner@xxxxxxxxxxx on behalf of Harbut, Chester
Sent: Mon 3/6/2006 5:49 PM
To: HAPS-L@xxxxxxxxxxx
Subject: [HAPS-L] Norepi effects on beta receptors
Hapsters,
The dilation that NE causes when it binds to beta-2 receptors on
coronary and skeletal muscle blood vessels confuses me a bit. If, when
smooth muscle such as is found in blood vessels is stimulated by NE
binding to alpha receptors causes it to contract, then how does NE cause
it to dilate? Does NE simply cause it to relax (reduction of vascular
tone)? It was one of those things that popped into my head WHILE I was
lecturing on it but I went right ahead and didn't introduce my ignorance
of the topic so as not to confuse my class (and myself?!) any more.
Plus, Selma Hayek was waiting outside the class for me and that somewhat
distracted my train of thought! Right!!
Thanks in advance for the input,
Chet
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