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| Description: This model, developed by Borbély and Ackerman in 1980, depicts how the circadian rhythm (process C) and homeostatic mechanism (process S) interact to regulate timing of sleep. As one spends time awake, the need for sleep builds up, creating sleep pressure (Sa). During sleep, this sleep pressure dissipates as the brain fulfills its need for sleep (Sb). The circadian process (C), by contrast, is the approximately 24-hour daily rest and activity rhythm of the body. When the circadian time for sleep onset (Co) matches a high level of sleep pressure, the individual falls asleep. (If sleep does not occur at this time, the need and drive for sleep will continue to build until it is impossible to ignore. If the setting is inappropriate for sleep, the brain will go to sleep, though for only a few seconds. These micro sleeps are momentarily restorative to the brain but not noticeable by the individual.) During sleep, both the homeostatic and circadian drives for sleep decrease, and when they reach a minimum, the person awakens. The circadian rhythm is a wave-like curve that peaks in the middle of the day and has a low point in the middle of the night. The homeostatic mechanism is also a wave-like curve, but with points at the top, instead of parabolic curves. These peak just as night time begins and are at their lowest in the morning. Picture Stats: Views: 23 Filesize: 63.58kB Height: 439 Width: 1021 Source: https://biology-forums.com/index.php?action=gallery;sa=view;id=49776 |