Brain blood flow autoregulation . a. is less sensitive to pH than to a decreased oxygen level b. causes constriction of cerebral blood vessels in response to a drop in systemic blood pressure c. is abolished when abnormally high CO2 levels persist d. is controlled by cardiac centers in the pons

b. causes constriction of cerebral blood vessels in response to a drop in systemic blood pressure

Explanation:

No matter what happens or fluctuations occur in the blood pressure of body the blood pressure to the brain is always kept constant by the necessary changes and means possible. The blood value is always maintained at 50mL per 100g of Brain Tissue. The constriction of blood vessel keep the blood pressure normal to the brain in case of low blood pressure. Otherwise, it can have deadly consequences.

Answer is C. Is abolished when abnormal high CO2 levels persist.

Explanation:

Autoregulation can be described or explained as an ability of some organs in the body, especially the brain in maintaining relatively constant blood flow despite changes in a pressure known as perfusion pressure.

Note that, the word 'perfusion' can be explained as the delivery of blood to a tissue through the circulatory system. The pressure that operate in this, i.e , that brings about the delivery of blood to a tissue is known as perfusion pressure.

In this case, it should be understood that, the persistence of abnormal high CO2 levels is one of the states that can abolished brain blood flow autoregulation. Others are brain tumor or stroke.