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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." It is regulated by circadian clocks.
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.
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).
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 ...
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.
In the study of chronobiology, entrainment refers to the synchronization of a biological clock to an environmental cycle. An example is the interaction between circadian rhythms and environmental cues, such as light and temperature. Entrainment helps organisms adapt their bodily processes according to the timing of a changing environment. [1]
Entrainment to environmental cycles is a trait with advantages, and is thus found in nearly all organisms. Many ecological relationships such as predator-prey interactions, pollinator behaviors, migration timing all require the synchronization of an organism’s biological clock with the 24-hour rhythm of planet. [12]
These rhythms are influenced by variable environmental cues, and in some species are influenced by internal cues. In a study conducted by Catalina Reyes, the authors took a further look into how red-eared sliders showed circadian and circannual rhythms in metabolism, and if metabolic rates overall influenced the circadian and circannual cues.