Question

multiple choice question
what is directly monitored by the central chemoreceptors?
o blood o₂ levels
o ph of the brain
o ph of the blood
o blood co₂ levels

Explanation:

Central chemoreceptors are located in the brain. They are sensitive to changes in the pH of the cerebrospinal fluid (which is related to the pH of the brain's extracellular fluid). When blood \(CO_2\) levels change, \(CO_2\) can cross the blood - brain barrier and affect the pH of the brain's extracellular fluid (through the reaction \(CO_2 + H_2O
ightleftharpoons H_2CO_3
ightleftharpoons H^+ + HCO_3^-\)). But the direct parameter they monitor is the pH of the brain (extracellular fluid). Blood \(O_2\) levels are mainly monitored by peripheral chemoreceptors (like the carotid and aortic bodies). The pH of the blood is not directly monitored by central chemoreceptors as the blood - brain barrier affects the access of some blood - borne substances. While blood \(CO_2\) can influence the central chemoreceptors' environment, it is the resulting pH change in the brain that is directly sensed.

Answer:

pH of the brain