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A zeitgeber (/ ˈ (t) s aɪ t ɡ eɪ b ər, ˈ z aɪ t-/ (T)SYTE-gay-bər, ZYTE-, German: [ˈtsaɪtˌɡeːbɐ]) is any external or environmental cue that entrains or synchronizes an organism's biological rhythms, usually naturally occurring and serving to entrain to the Earth's 24-hour light/dark and 12-month cycles.
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 ...
Endogenous: Growing or working from within an organism; intrinsic. Entrainment: The process an organism undergoes when synchronizing endogenous rhythms to a Zeitgeber. Free-Running Period (FRP): The length of time it takes for an organism's endogenous rhythm to repeat without Zeitgebers in constant conditions (LL or DD).
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).
Within each cycle, the time period during which the process is more active is called the acrophase. [4] When the process is less active, the cycle is in its bathyphase or trough phase. The particular moment of highest activity is the peak or maximum; the lowest point is the nadir. How high (or low) the process gets is measured by the amplitude.
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]
Colin Stephenson Pittendrigh (October 13, 1918 – March 19, 1996) [1] was a British-born biologist who spent most of his adult life in the United States. Pittendrigh is regarded as the "father of the biological clock," and founded the modern field of chronobiology alongside Jürgen Aschoff and Erwin Bünning.
Central pattern generators (CPGs) are self-organizing biological neural circuits [1] [2] that produce rhythmic outputs in the absence of rhythmic input. [3] [4] [5] They are the source of the tightly-coupled patterns of neural activity that drive rhythmic and stereotyped motor behaviors like walking, swimming, breathing, or chewing.