What does the brain need to work properly?

To work at its best, the brain needs a constant supply of oxygen and glucose, which is carried to the brain by the blood. Because a constant supply of blood is so essential, the arteries supplying blood to the brain have the ability to narrow and widen as needed to ensure adequate oxygen and nourishment. Likewise, blood vessels within the brain widen and narrow to regulate the flow of blood to those areas of the brain working hardest.