SNS dilation of blood vessels

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SNS dilation of blood vessels

Post by angelo » Sat Jan 21, 2006 12:27 am

The sympathetic nervous system contracts blood vessels, causing a higher blood pressure. But how does an increase in pressure prime the body for a response?

And is the contraction purely by activation of smooth muscle tissue at the blood vessel?

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Post by sdekivit » Sat Jan 21, 2006 5:19 pm

the contraction of the smooth muscles in the vascular walls contract as a part of autoregulation. It protects the tissues for overperfusion and thus damage.

--> high blood pressure and low blood pressure are sensed by peripheral baroreceptors in sinus caroticus and aortic arch and also by the stretch receptors in the atria which then secrete ANP

In the case of high blood pressure:

1. baroreceptor fire less and thereby less supression of the parasympathetic impulses resulting in drecreased heart rate and cardiac output.

2. atria secrete ANP which acts on the kidneys. It results in less renine secretion by the kidney, less ADH and aldosteron secretion, thereby the body doesn't conserve water and salts maintaining blood osmolarity and lowering blood pressure.

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