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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).
In addition to mood, learning and memory become impaired when the circadian system shifts due to light stimuli, [6] [20] which can be seen in studies modeling jet lag and shift work situations. [4] Frontal and parietal lobe areas involved in working memory have been implicated in melanopsin responses to light information. [20]
Circadian rhythms have been documented for centuries. For example, French astronomer Jean-Jacques d’Ortous de Mairan noted the periodic 24-hour movement of Mimosa plant leaves as early as 1729. However, science has only recently begun to uncover the cellular mechanisms responsible for driving observed circadian rhythms.
A circadian clock, or circadian oscillator, also known as one’s internal alarm clock is a biochemical oscillator that cycles with a stable phase and is synchronized with solar time. Such a clock's in vivo period is necessarily almost exactly 24 hours (the earth's current solar day). In most living organisms, internally synchronized circadian ...
The Rev-Erb proteins are members of the nuclear receptor (NR) superfamily of intracellular transcription factors and key regulatory components of the circadian clock. There are two forms of the receptor, Rev-Erb alpha and Rev-Erb beta, which are each encoded by a separate gene (NR1D1 and NR1D2, respectively). [1] [2]
The SCN of the hypothalamus contains an endogenous pacemaker that regulates circadian rhythms. [4] The zeitgeber found to have the most profound effect on the SCN is light, which is the form of stimulation of which conversion is needed for it to be processed by the brain. Neurotransmitters that travel the RHT are responsible for delivering this ...
It also regulates several physiological processes under circadian control, including metabolic and immune pathways. [ 6 ] [ 7 ] Rev-Erbɑ mRNA demonstrates circadian oscillation in its expression, and it is highly expressed in mammals in the brain and metabolic tissues such as skeletal muscle , adipose tissue , and liver .
The circadian clock refers to a biological mechanism that governs multiple biological processes causing them to display an endogenous, entrainable oscillation of about 24 hours. These rhythms have been widely observed in plants, animals, fungi and cyanobacteria.