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Circadian Rhythm is the daily activity cycle that drives the rhythms of our body- from digestion to hormone secretions to our ability to sleep.
The timing of human sleep is governed by the length of time since a person last slept and by their internal body clock. The body clock or circadian clock controls the timing of human sleep with a rhythm that is regulated by a tiny region of the brain called the suprachiasmatic nucleus (SCN). The SCN is located in the hypothalamus and signals from the SCN help us stay awake and counteract the effects of fatigue. These signals peak in the evening, when the drive for sleep is high, and then diminish when bedtime approaches1.
In most people, circadian rhythms match the 24-hour day by adjusting to environmental cues, like light. When a person's body clock is mismatched with their sleeping and waking schedule, it may create a circadian rhythm sleep disorder.
References
- C. A. Czeisler and S. B. Khalsa, in Principles and Practice of Sleep Medicine, M. H. Kryger, Roth T., W. C. Dement, Eds. (W.B.Saunders Company, Philadelphia, 2005).
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