how long do brain cells typically live
Skin cells live about two or three weeks. Colon cells have it rough: They die off after about four days. Sperm cells have a life span of only about three days, while brain cells typically last an entire lifetime (neurons in the cerebral cortex, for example, are not replaced when they die). There's nothing special or significant about a seven-year cycle, since cells are dying and being replaced all the time.