Question

Central chemoreceptors detect a decrease in pH in interstitial fluids in the brain. What is the response of the medulla to maintain delivery of oxygen to cells?

a. A feedback loop is initiated that indirectly increases parasympathetic activity which results in vasoconstriction and a rise in blood pressure.
b. A feedback loop is initiated that indirectly increases parasympathetic activity which results in vasodilation and a decrease in blood pressure.
c. A feedback loop is initiated that indirectly decreases sympathetic activity which results in vasodilation and a decrease in blood pressure.
d. A feedback loop is initiated that indirectly increases sympathetic activity which results in vasoconstriction and a rise in blood pressure.

Answer 1

The medulla responds to a decrease in pH due to increased carbon dioxide by increasing sympathetic activity, resulting in increased cardiac output and peripheral vasoconstriction, which raises blood pressure to improve oxygen delivery.

Step-by-step explanation:

When central chemoreceptors detect a decrease in pH in interstitial fluids in the brain, which indicates an increase in carbon dioxide and hydrogen ion levels, a feedback loop is initiated.

This response of the medulla includes the stimulation of the cardioaccelerator and vasomotor centers, leading to an increase in cardiac output and peripheral vasoconstriction.

This process results in a rise in blood pressure, thereby enhancing the delivery of oxygen to cells and the removal of carbon dioxide from the bloodstream. The response does not involve an increase in parasympathetic activity but rather a decrease in parasympathetic influence, allowing sympathetic activity to dominate and cause these effects.