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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).
A circadian rhythm is an entrainable, endogenous, biological activity that has a period of roughly twenty-four hours. This internal time-keeping mechanism is centralized in the suprachiasmatic nucleus (SCN) of humans, and allows for the internal physiological mechanisms underlying sleep and alertness to become synchronized to external environmental cues, like the light-dark cycle. [4]
A second wind may come more readily at certain points of the circadian (24hr) biological clock than others.. Second wind (or third wind, fourth wind, etc.), a colloquial name for the scientific term wake maintenance zone, is a sleep phenomenon in which a person, after a prolonged period of staying awake, temporarily ceases to feel drowsy, often making it difficult to fall asleep when exhausted.
Waking up in the middle of the night is common, ... you roll over to check the clock and find it’s 3 a.m. That’s the same time you woke up last night. And the night before.
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In regards to pupil dimensions, newborns' pupils grow from approximately 2.2 mm to an adult length of 3.3 mm. [2] A one-month-old infant can detect a light threshold only when it is approximately 50 times greater than that of an adult. By two months, the threshold decreases measurably to about ten times greater than that of an adult.
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