In very simplistic terms, sleep is regulated by two body systems: the homeostatic sleep drive and the circadian biological clock.
Homeostatic sleep drive is a fancy way of saying that we get tired when we have been awake for a long period of time. If this were to only process regulating our sleep patterns, then it would mean that we would be most alert as our day was starting out, and that the longer we were awake, the more we would feel like sleeping.
But it’s obviously not as simple as this, as anyone who has struggled to fall asleep at night has experienced, and that is in part due to the fact that our circadian biological clock regulates the timing of periods of sleepiness and wakefulness throughout the day. So if you’ve ever felt more sleepy at noon than midnight, that’s most likely a result of your circadian rhythm. (more…)