The blood vessels supplying the tissues of the brain. The brain derives most of its energy from OXYGEN and GLUCOSE supplied via the bloodstream. Under normal conditions, cerebral blood flow and energy use are tightly coupled, and the brain must adapt to local alterations in energy requirement by regulating the amount of bloodflow accordingly.
Blood reaches the brain via the carotid and basilar arteries, which surround the brain in a complete arterial circle, known as the CIRCLE OF WILLIS.
This circular arrangement may preserve perfusion to the entire brain in the event that one artery becomes blocked. From this circle arise the anterior, middle and posterior cerebral arteries, which divide into pial arteries. These run over the surface of the brain, and subdivide into short arterioles, which give rise to a high density of capillaries that ultimately supply nerve cells with blood. These capillaries are highly responsive to local changes in potassium ions, resulting in increased blood flow during neuronal activity. Because cerebral blood flow and neuronal activity are inherently linked, studies of cerebral blood flow employing radiolabelled tracers have been used both clinically to estimate disruptions of blood flow in disease or injury, and experimentally to examine the effects of cognition and pharmacological intervention on neuronal activity.
