Brain activity regulates brain circulation by controlling cardiac output and blood pressure. Emotions, especially anger, are strong brain events that act on the cardiovascular system; heart rate increases and blood pressure rises, often dramatically.

Cognitive tasks increase blood flow and metabolic rate in the regions of the brain that process the task. Changes in localized blood flow are the basis of functional imaging studies that reveal the modules in the brain that are active during task processing.

The cerebral microvessels have a unique feature, the blood-brain barrier, which protects sensitive brain cells from disturbing elements circulating in the blood.

Endothelial cells line blood vessel. Their behavior regulates permeability. In the brain, tight intercellular junctions limit endothelial permeability. A variety of chemical signals to and from endothelia cells control blood vessel transactions with glial cells and neurons. Cerebral vessels have nerves supplies --  sympathetic, parasympathetic, and sensory nerve fibers. Gaseous transmitters such as nitric oxide (NO) dilate small blood vessels and participate in the regulation of blood flow