FIG. 3.

Potential mechanisms involving the autonomic nervous system that might attempt to restore homeostasis in the context of cerebral blood flow (CBF) and cerebral perfusion pressure (CPP) derangement. A decrease in CPP and/or CBF might activate the two branches of the autonomic nervous system (ANS). The parasympathetic system causes brain vessel vasodilatation focused on maintaining brain CBF. At the same time, the sympathetic system increases arterial blood pressure (ABP) and therefore CPP. These assumptions could be considered in the context of not deranged ANS. HR, heart rate.