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PHGY 210 (301)
Ann Wechsler (112)
Lecture 14

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PHGY 210
Ann Wechsler

Lecture 14 Neural control of the heart and vessels: The parasympathetic control of the heart rate, medulla oblongata to a ganglion, through acetylcholine transduction, nicotinic receptor. Post-ganglionic nerve transduce Ach onto S.A. node cells, muscarinic receptor. Atropine will collect at the clefts between S.A. nodes and post-ganglionic nerve cells, will speed up heart rate as parasympathetic system control is removed. Sympathetic control of the heart rate is controlled by acetylcholine and then norepinephrine at the beta-adrenergic receptor. Beta-agonist would speed up the heart rate by making it more sensitive, an antagonist would competitively bind. If norepinephrine is dumped on the ventricular muscle would increase calcium inflow like on the S.A. nodes and increase contraction force. Sympathetic contractions do not follow the normal EDV/SV ratios, they have their own curves. Most of the vessels in the bodies (all the way down to venules and arterioles), are controlled by the sympathetic vessels, using an alpha-adrenergic receptor. Activation would lead to constrictions of the vessels. Adrenal Glands: cells of the adrenal glands are ganglion cells that lost their axon, and symthesize norepinephrine and epinephrine. 2/3 epi and 1/3 norepi, epi to the SV nodes and norepi to the smooth muscles of vessels to constrict. Blood Pressure Control: Baroreceptors ensure that when postures change, one does not faint, functions in 1-2seconds. The kidneys, on the other hand, takes hours to days to change. Maximum feedback gain is an indicator of how strong the reflex is. When BP drops, different pathways have different effects, e.g. baroreceptors cannot function any better at 40 than at 50, and h
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