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Although circadian rhythms are endogenous, they are adjusted to the local environment by external cues called zeitgebers (from German Zeitgeber (German: [ˈtsaɪtˌɡeːbɐ]; lit. ' time giver ')), which include light, temperature and redox cycles. In clinical settings, an abnormal circadian rhythm in humans is known as a circadian rhythm sleep ...
A circadian rhythm is an entrainable, endogenous, biological activity that has a period of roughly twenty-four hours. This internal time-keeping mechanism is centralized in the suprachiasmatic nucleus (SCN) of humans, and allows for the internal physiological mechanisms underlying sleep and alertness to become synchronized to external environmental cues, like the light-dark cycle. [4]
These variants occur near genes known to be important in photoreception and circadian rhythms. [37] The variant most strongly associated with chronotype occurs near RGS16, which is a regulator of G-protein signalling and has a known role in circadian rhythms. In mice, gene ablation of Rgs16 lengthens the circadian period of behavioural rhythm.
Because circadian clocks synchronize human sleep-wake cycles to coincide with periods of the day during which reward potential is highest – that is, during the daytime [16] – and recent studies have determined that daily rhythms in reward activation in humans are modulated by circadian clocks as well, [16] external influences on those ...
The term polyphasic sleep was first used in the early 20th century by psychologist J. S. Szymanski, who observed daily fluctuations in activity patterns. [2] It does not imply any particular sleep schedule. The circadian rhythm disorder known as irregular sleep-wake syndrome is an example of polyphasic sleep in
These disorders are caused by discrepancies between one’s circadian rhythm and the light/dark cycle of the environment. People with a sleep disorder experience insomnia or hypersomnia. There are a number of sleep disorders that light therapy are effective in treating, such as delayed sleep phase type (DSPT) and advanced sleep phase type (ASPT ...
According to the International Classification of Sleep Disorders, Revised (ICSD-R, 2001), [10] the circadian rhythm sleep disorders share a common underlying chronophysiologic basis: The major feature of these disorders is a misalignment between the patient's sleep-wake pattern and the pattern that is desired or regarded as the societal norm...
The best studied rhythm in chronobiology is the circadian rhythm, a roughly 24-hour cycle shown by physiological processes in all these organisms. The term circadian comes from the Latin circa, meaning "around" and dies, "day", meaning "approximately a day." It is regulated by circadian clocks.