Physiological mechanisms controlling cerebral blood flow.

The major conceptions of cerebral blood flow (CBF) control developed in the 19th and 20th centuries are listed. The systems of CBF regulation are considered from the viewpoint of automatic control. In the classification of CBF regulation mechanisms, 4 types are identified. The effectors of CBF regulation, i.e. the specific arterial segments through which each type of regulation is accomplished, were found to be mainly the major arteries of the brain and the small pial arteries rather than the intracerebral arterioles. Review of controlling influences on these effectors of regulation, (myogenic, humoral and neurogenic), show that priority should be given to neurogenic mechanisms. Several criteria governing efficiency of CBF regulation are proposed. Review of interactions of different types of CBF regulation shows that there may be both synergistic and antagonistic relationships. Information about the processes is important for medical practice.