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A circadian rhythm (/ s ər ˈ k eɪ d i ə n /), or circadian cycle, is a natural oscillation that repeats roughly every 24 hours.Circadian rhythms can refer to any process that originates within an organism (i.e., endogenous) and responds to the environment (is entrained by the environment).
The first published usage of the term "phase response curve" was in 1960 by Patricia DeCoursey. The "daily" activity rhythms of her flying squirrels, kept in constant darkness, responded to pulses of light exposure. The response varied according to the time of day – that is, the animals' subjective "day" – when light was administered.
A circadian clock, or circadian oscillator, also known as one’s internal alarm clock is a biochemical oscillator that cycles with a stable phase and is synchronized with solar time. Such a clock's in vivo period is necessarily almost exactly 24 hours (the earth's current solar day). In most living organisms, internally synchronized circadian ...
Jet lag occurs when one’s circadian rhythm is out of sync with the environment, and this is usually caused by travel across time zones. People with jet lag experience symptoms such as fatigue, insomnia, headaches, etc. Light therapy has been hypothesized to help mitigate these symptoms.
Circadian literally translates to "about a day" in Latin. This refers to the human 24-hour cycle of sleep and wakefulness. This cycle is driven by light. The human body must photoentrain or synchronize itself with light in order to make this happen. The rod cells are the photoreceptor cells in the retina capable of sensing light. However, they ...
Biological rhythms are endogenous; they persist even in the absence of environmental cues as they are driven by an internal mechanism, the circadian clock being the best characterized. Of the several possible cues, known as zeitgebers (German for 'time-givers'), which can contribute to entrainment of the circadian clock, light has the greatest ...
A study published in the journal BMJ showed a 24-percent jump in heart attack risk the Monday after daylight saving time kicked off, ... go up after the time ... circadian rhythms to the new time ...
The physiological changes that follow these clocks are known as circadian rhythms. Because the endogenous period of these rhythms are approximately but not exactly 24 hours, these rhythms must be reset by external cues to synchronize with the daily cycles in the environment. [1] This process is called entrainment. One of the most important cues ...