Why does it take approximately 24 hr for a full ventilatory ...

[jman1234]

Why does it take approximately 24 hr for a full ventilatory response to develop to acute hypox-emia?
 
  a. Initial cerebrospinal fluid alkalemia blunts the hypoxic ventilatory stimulus.
  b. Peripheral chemoreceptors are slow to re-spond to decreased blood O2 levels.
  c. Renal compensation for respiratory alkalo-sis increases chemoreceptor sensitivity.
  d. A full ventilatory response is not possible until after the muscles become fatigued.

Question 2

Which respond more rapidly to high levels of CO2?
 
  a. Aortic chemoreceptors
  b. Carotid chemoreceptors
  c. Central chemoreceptors
  d. Ventral respiratory centers

[l.stuut]

Answer to Question 1

ANS: A
High altitude causes a healthy person's ventilation to increase because low barometric pressure decreases the inspired PO2, and thus the arterial PO2, which in turn raises the sensitivity of pe-ripheral chemoreceptors to hydrogen ions. The resulting increase in ventilation is less than ex-pected though, because hyperventilation lowers the PaCO2 and raises arterial pH. The increased pH depresses the medullary respiratory center, counteracting the excitatory effect of a low PaO2 on peripheral chemoreceptors.

Answer to Question 2

ANS: B
The carotid chemoreceptors respond to increased arterial hydrogen ion concentration more rapid-ly than do the central chemoreceptors.