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Old 02-12-2011
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Question Carotid Sinus to Medulla Pathway

I was wondering if anyone can explain the carotid sinus mechanism to me?
I understand that its a dilation in the internal carotid that has baroreceptors in it which monitor blood pressure. Increases in BP will lead to increased firing which is carried by cranial nerves 9 and 10 to the medulla.
Increased firing will lead to an increase in parasympathic response which will decrease the blood pressure by decreasing HR etc.
But I am missing some pieces of the puzzle--which receptor in medulla receives this info? Is it solitary nucleus or the dorsal motor nucleus? Also what increases the parasympathetic firing?
Sorry for the long question but I have read this so long ago and I can't remember the details, can't even find the info in my notes

Would really appreciate any help I can get on this.

Thanks!
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Old 02-12-2011
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Ok so finally found it, the info goes to tractus solitarius of the medulla, which sends secondary signals to inhibit the vasoconstrictor center of medulla and excite the vagal parasympathetic center (assuming there was an increase in firing). Net effects--
-vasodilation of arterioles and veins
-decreased heart rate and strength of contraction
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Old 02-23-2011
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The baroreceptors in the aortic arch and the carotid sinus travel via the depressor nerve and the Hering's nerve, in the vagus and glossopharyngeus, respectively. They terminate (form synapse) in the NTS, which is the most important relay centre where fibers from baro and chemoreceptors form synapses. Increase firing of the above mentioned nerves causes the NTS, primarily to stimulate the caudal portion of the ventrolateral medulla (CVLM) which in turn inhibits the rostral ventrolateral medulla (RVLM, pressor area, has bulbospinal neurons that project to the sympathetic preganglionic neurons-SPN). Decreased firing of the RVLM results in restriction of sympathetic outflow to SPN causing vasodilation of small blood vessels, reduced cardiac output and finally fall in blood pressure. This is the main baroreceptor traffic. Other pathway is from the NTS to the nucleus ambiguus which increases the vagus tone and additionally helps lowering BP.
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Cardiovascular-, Nervous-System-, Physiology-

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