What effect does cerebral ischemia have on CBF autoregulation?

What effect does cerebral ischemia have on CBF autoregulation?

• A. CBF autoregulation is ablated
• B. CBF autoregulation is ablated at low cerebral perfusion pressures but remains intact at high cerebral perfusion pressures
• C. CBF autoregulation is ablated at high cerebral perfusion pressures but remains intact at low cerebral perfusion pressures
• D. The CBF autoregulatory curve is shifted to the right

Answer: (A)

Autoregulation of cerebral blood flow keeps brain perfusion steady by adjusting vessel diameter in response to changes in perfusion pressure. When cerebral ischemia occurs, energy failure depletes ATP in vascular smooth muscle and endothelium, impairing their ability to constrict or dilate in response to pressure or metabolic cues. With this loss of responsiveness, CBF no longer stays constant as perfusion pressure changes; it becomes pressure-passive. In other words, the autoregulatory mechanism is ablated, so blood flow tracks the systemic pressure rather than remaining stabilized.

Autoregulation of cerebral blood flow keeps brain perfusion steady by adjusting vessel diameter in response to changes in perfusion pressure. When cerebral ischemia occurs, energy failure depletes ATP in vascular smooth muscle and endothelium, impairing their ability to constrict or dilate in response to pressure or metabolic cues. With this loss of responsiveness, CBF no longer stays constant as perfusion pressure changes; it becomes pressure-passive. In other words, the autoregulatory mechanism is ablated, so blood flow tracks the systemic pressure rather than remaining stabilized.