Blood Flow Velocity in the Middle Cerebral Artery

The brain of an adult person constitutes approximately only 2% of the body mass. Disproportionately, it receives roughly 15% of cardiac output and consumes nearly 20% of the total oxygen utilization at rest. Through the evolution of the human brain, the need for oxygen in brain tissue has been increasing with increasing cerebral tissue mass. In the mass of the brain relative to the body, a disproportionately large blood flow to the brain may be originally related to a delicate situation of or an adaptation of the cardiovascular system to the orthostatic stress in standing posture. Since the brain tissues are extremely fragile in oxygen deficiency, an adequate and continuous supply of oxygenated blood flow to the cerebral tissues is essential for sustaining the brain function as well as for keeping tissues alive. The blood flow in the middle cerebral artery (MCA) maintains about 80% of the flow volume arriving at the cerebral hemisphere. Changes in blood flow are also closely related to changes in cerebral metabolism.