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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."
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).
Overview, including some physiological parameters, of the human circadian rhythm ("biological clock"). Chronobiology is a field of biology that examines timing processes, including periodic (cyclic) phenomena in living organisms, such as their adaptation to solar- and lunar-related rhythms. [1] These cycles are known as biological rhythms.
Any biological process in the body that repeats itself over a period of approximately 24 hours and maintains this rhythm in the absence of external stimuli is considered a circadian rhythm. [4] It is believed that the brain's suprachiasmatic nucleus (SCN), or internal pacemaker, is responsible for regulating the body's biological rhythms ...
Theories published state the equations for the cycles as: physical: (/), emotional: (/), intellectual: (/), where indicates the number of days since birth. Basic arithmetic shows that the combination of the simpler 23- and 28-day cycles repeats every 644 days (or 1 3 ⁄ 4 years), while the triple combination of 23-, 28-, and 33-day cycles repeats every 21,252 days (or 58.18+ years).
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.
Circadian clock, a molecular mechanism that results in a circadian rhythm in a living organism; Circadian rhythm, biological process that displays an oscillation about 24 hours, such as the human sleep-wake cycle (the "body clock") Epigenetic clock, a set of DNA sites whose methylation levels can be used to measure aging throughout the body
In contrast, circadian rhythms complete one cycle daily, while infradian rhythms such as the menstrual cycle have periods longer than a day. The Oxford English Dictionary 's definition of Ultradian specifies that it refers to cycles with a period shorter than a day but longer than an hour.