Under normal conditions, all he energy used by the brain cells is supplied by glucose derived from the blood. Only about a 2-minutes supply oi glucose normally stored as glycogen m the neurons at any given time. A special feature of glucose delivery to the neurons is that its transport into the neurons through the cell membrane is not dependent on insulin, even though insulin is required for glucose transport into most other body cell. GUYTONp767
The brain is quite different from most other tissues of the body in that insulin has little effect on uptake or use of glucose. Instead, the brain cells are permeable for glucose and can use glucose without the intermediation of insulin. The brain cells are also quite different from most other cells of the body in that they normally use only glucose for energy and can use other energy substitutes, such as fats, only with difficulty. Therefore, it is essential that the blood glucose level always be maintained above a critical level, which is one of the most important functions of the blood glucose control system. GUYTONP965
|