Search results
Results From The WOW.Com Content Network
Light resets the biological clock in accordance with the phase response curve (PRC). Depending on the timing, light can advance or delay the circadian rhythm. Both the PRC and the required illuminance vary from species to species, and lower light levels are required to reset the clocks in nocturnal rodents than in humans. [104]
In vertebrates, the master circadian clock is contained within the suprachiasmatic nucleus (SCN), a bilateral nerve cluster of about 20,000 neurons. [10] [11] The SCN itself is located in the hypothalamus, a small region of the brain situated directly above the optic chiasm, where it receives input from specialized photosensitive ganglion cells in the retina via the retinohypothalamic tract.
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
While circadian rhythms are defined as regulated by endogenous processes, other biological cycles may be regulated by exogenous signals. In some cases, multi-trophic systems may exhibit rhythms driven by the circadian clock of one of the members (which may also be influenced or reset by external factors).
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, most notably the circadian clock. Of the several possible cues (known as zeitgebers, German for 'time-givers') that can contribute to entrainment of the circadian clock, light has the greatest impact.
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.
This results in changes in the expression of the various clock proteins is what allows the organism to undergo photoentrainment. [9] In single celled organisms, circadian rhythms are believed to be generated without the use of a TTFL, but rather with a 3 protein complex called the KaiABC Complex. The mechanism of entrainment in this system is ...