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Old 05-20-2011
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Question Chemoreceptor Response to Increased PCO2!

An anxiety induced hyperventilation can often be successfully treated by the individual rebreathing the expired air from a paper bag held over the mouth region. Rebreathing this air can increase tehe arterial PCo2 toward the normal range. Which of the following is the mechanism by which the increased PCo2 would first be detected?

A) Central chemoreceptors responding directly to the increased arterial PCo2
B) Central chemoreceptors responging to increases in cerebrospinal PCo2
C) Increased cerebral blood flow increasing the diffusion gradient for CO2 toward the central chemoreceptors
D) Peripheral chemoreceptors responding directly to the increased arterial PCo2
E) Peripheral chemoreceptors responding directly to the increased systemic venous PCo2

can some one plz explain clearly!!! thanks in advance :-)
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Old 05-20-2011
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OK, we have the carotid bodies which contain a baroreceptor and a chemoreceptor.
and we have the aortic arch which also contain a baroreceptor and a chemoreceptor.
-the receptors in the aortic arch respond only to increase in blood pressure and its respond is only to decrease blood pressure b/c the aortic arch receptors transmit to medula via the vagus nerve which is under parasympathetic control.
-the receptors in the carotid sinus and body respond to increase and to decrease in blood pressure.

OK. the question ask about the first receptor to respond.
the answer is D
1- peripheral chemoreceptors respond to decrease in po2, to increase in pco2 and to decrease in PH of BLOOD.
2. central chemoreceptors respond to changes in PH, pco2 of BRAIN INTERSTITIAL FLUID.
3-this response of the chemoreceptor is influenced by ARTERIAL CO2, so can not be the first to respond.
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The above post was thanked by:
drgsarunprasath (05-20-2011), Taiwan_Guy (05-21-2011)



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Nervous-System-, Physiology-, Respiratory-, Step-1-Questions

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