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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).
Awake craniotomy is a neurosurgical technique and type of craniotomy that allows a surgeon to remove a brain tumor while the patient is awake to avoid brain damage.During the surgery, the neurosurgeon performs cortical mapping to identify vital areas, called the "eloquent brain", that should not be disturbed while removing the tumor.
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.
mPer1 and mPer2 are necessary for clock function in the brain, while mPer3 only plays a discernible role in the circadian rhythms of peripheral tissues. Knocking out either mPer1 or mPer2 causes a change in period, with mPer1 knockouts free-running with a shorter period and mPer2 knockouts free running with a longer period compared to the ...
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.
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The symptoms are caused by a circadian rhythm that is out of sync with the day–night cycle of the destination, [8] as well as the possibility of internal desynchronisation. Jet lag has been measured with simple analogue scales, but a study has shown that these are relatively blunt for assessing all the problems associated with jet lag.
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.