The brain is "Command Central" for most of the body's major functions. It controls body temperature, blood pressure, heart rate and breathing. It processes input from the five senses: sight, smell, touch, taste, and sound. And it controls physical motion, thinking, dreaming, and human emotion. But while the brain can sense pain in other parts of the body, it cannot sense pain in itself. Nor can it store oxygen or blood sugar. So the brain needs a constant supply of blood in order to keep functioning.
Whenever a specific part of your brain is activated, blood vessels widen to increase blood flow to that area. Strokes, clogged arteries and brain tumors can all block or reduce the flow of blood. When this happens, brain cells can be damaged or die, leading to death or permanent disability. Scientists aren't sure exactly how increased blood flow in the brain is activated, but if they can find out, it could help them better understand and control such diseases as Alzheimer's and stroke.
Sometimes reducing the blood flow to certain areas of the brain can be a good thing. Recent studies on Chinese acupuncture have found that sticking needles in certain points on the hand decreases blood flow to certain areas of the brain associated with mood, pain, and cravings. Reducing blood flow to those areas can trigger the release of endorphins, the brain's natural pain-relieving chemicals. Some headache medicines contain caffeine for similar reasons. The caffeine not only blocks the action of a natural brain chemical associated with sleep, but it causes the blood vessels to constrict, relieving the throbbing pain associated with bad headaches.
The American Association of Physicists in Medicine provided information for the TV story that accompanies this web page.