Question

If the arterial blood pressure in the brain is suddenly decreased, the flow through arterioles in the brain will immediately fall and then which of these will occur next

A. Brain arterioles will constrict to accelerate blood flow through the brain capillaries
B. Brain arterioles will dilate due to a decrease in levels of CO2
C. Blood flow will remain at the new, lower level due to reactive hyperemia
D. Blood flow will rise to levels above normal due to excess O2 levels
E. Blood flow will return toward its original level due to flow autoregulation

Answer 1

The correct answer is option E. Following a decrease in arterial blood pressure in the brain, blood flow initially falls and then returns toward its original level due to flow autoregulation, which triggers dilation of brain arterioles.

Step-by-step explanation:

When arterial blood pressure in the brain suddenly decreases, the initial response involves a physiological mechanism known as autoregulation.

After an immediate fall in flow through the arterioles due to the decreased pressure, autoregulatory mechanisms will rapidly respond to restore adequate blood flow. Thus, in answer to the student's question, what occurs next is that brain arterioles will dilate to increase blood flow and compensate for the reduced arterial pressure.

This process is driven by local factors in response to the reduced availability of oxygen and nutrients, as well as the increased presence of metabolic waste products like carbon dioxide (CO2). So the correct option, in this case, is E. Blood flow will return toward its original level due to flow autoregulation.