TYK34

Under normal conditions, the MAIN control of respiration in the body responds to changes in what substance?

A. CSF hydrogen ion concentration

B. Arterial oxygen concentration

C. Arterial carbon dioxide concentration

D. Arterial bicarbonate concentration

Answer

The answer is A. The central, chemoreceptors, located near the surface of the ventrolateral medulla, are anatomically separated from the medullary respiratory center. They respond to changes in hydrogen ion concentration in the adjacent cerebrospinal fluid rather than to changes in arterial Pco2 or pH. Since CO2 rapidly equilabrates through the blood-brain barrier into the cerebrospinal fluid, the central chemoreceptors are quickly stimulated by systemic hypercarbia. Ventilatory responses of the chemoreceptors to acute metabolic acid base distrubances are not as robust. Response to changes in metabolic components are limited because changes in the hydrogen ion concentration in arterial blood are not as quickly transferred to the CSF. In chronic acid-base disturbances the pH of the CSF does not change very much to ventilatory changes. Under these circumstances, ventilation becomes more dependent on the hypoxic response of peripheral chemoreceptors.

Notes

Pappenheimer, J. R., et al. "Role of cerebral fluids in control of respiration as studied in unanesthetized goats." American Journal of Physiology--Legacy Content 208.3 (1965): 436-450.[1]

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