ssrpk
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increase in ICP --> evokes sympathetic discharge to the heart --> increase blood pressure --> baroreceptor reflex activation --> bradycardia!
in short bradycardia in the face of head trauma etc. is an ominous sign!
now why does it happen? whenever intracranial pressure rises, it compreses the arterioles of chemoreceptor trigger zone, thus resulting in local hypoxia and low po2 is a very potent mediator of cerebral blood flow thats why it leads to inc. sympathetic outflow!
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| Luckyall
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Agree with you till the part where you explained " why"
Central ChemoRec are responsible for Cushing reaction but these Central ChemoRec dont direcly respond to PO2, they resp. to PCO2 and PH of brain interstit fluid wich in turn are influenced by arterial Pco2. So incr ICP---> compression of cerebr vessels-->cerebr ischemia and incr PCO2. The vasomotor center directs and incr S and incr PS, so incr BP and decr HR
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| ssrpk
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hmnmmm thanks for the correction!
yeah PO2 is monitored by the peripheral chemoreceptors not central!
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| Ig F
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wow..thnx for making it easy......
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