Sleep and Circadian Systems

The suprachiasmatic nucleus of the brain is the body’s “master clock”. However, all of the cells of our body signal time. Our daily habits are zeitgebers “time givers”. Light, meals, exercise, social life signal alertness. Our time spent alert and awake generate adenosine that creates the sleep pressure that puts us to sleep at night (process S). When process S is not competing with process C (dictated by light), the body knows it is physiologic night – time to sleep.