While lecturing to a group of physiology students, the instructor asks, "What metabolic factors cause vasodilation of cerebral vessels thereby increasing cerebral blood flow to the brain?" The student with the best response would be:

Question

A) Increased oxygen saturation
B) Increased carbon dioxide level
C) Decreased serum sodium level
D) Decreased hydrogen ion concentration

Answer 1

Ans: B
Feedback:
At least three metabolic factors affect cerebral blood flow: carbon dioxide, hydrogen ion, and oxygen concentration. Increased carbon dioxide provides a potent stimulus for vasodilation—a doubling of the PCO2 in the blood results in a doubling of cerebral blood flow. Increased hydrogen ion concentrations also increase cerebral blood flow, serving to wash away the neurally depressive acidic materials. Decreased oxygen concentration also increases cerebral blood flow. Low sodium is a hypoosmolar intravascular environment that will pull sodium out of the cells—a response unrelated to blood cell volume or flow.