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Circadian clock

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noun, plural: circadian clocks

A molecular mechanism resulting in a circadian rhythm in a living organism


A circadian clock regulates the circadian rhythm in organisms. Circadian rhythm is a biological rhythm involving a 24-hour cycle. The biological and behavioural pattern of an organism is in sync with the day-night cycle. The term circadian came from the Latin term circa meaning about and diem meaning a day. Under normal conditions, the body oscillates with a period of about 24 hours. It falls into synchronism upon receiving sufficient daily signals from environmental cues, particularly daylight and darkness. The circadian clock in humans and other mammals is located in the suprachiasmatic nuclei, which in turn is a tiny cluster of about ten thousand nerve cells in the hypothalamus.1

The circadian clock is typically comprised of the following components: (1) a central biochemical oscillator with a period of about 24 hours that keeps time, (2) a series of input pathways to the central oscillator in order to allow the clock to fall into synchronism, and (3) a series of output pathways associated with the phases of the oscillator regulating rhythms in biochemistry, physiology, and behavior in an organism.2


  • circadian oscillator

See also:

1 Hedge, A. (2013). Biological Rhythms. Retrieved from [[1]]
2 Circadian clock. Retrieved from [[2]].