Circadian rhythm's or 24-hour cycles are driven by the body's "biological clock." The "biological clock" is regulated by light or darkness, which can make the body think it is time to sleep or wake up.

The 24-hour circadian rhythm controls functions such as:

ByHealthwise Staff
Primary Medical ReviewerKathleen Romito, MD - Family Medicine
Specialist Medical ReviewerAlfred Lewy, MD, PhD - Psychiatry
Last RevisedJuly 7, 2010

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