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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).
Polar night is a phenomenon that occurs in the northernmost and southernmost regions of Earth when the Sun remains below the horizon for more than 24 hours. This only occurs inside the polar circles. [1] The opposite phenomenon, polar day or midnight sun, occurs when the Sun remains above the horizon for more than 24 hours.
Polyphasic sleep is the practice of sleeping during multiple periods over the course of 24 hours, in contrast to monophasic sleep, which is one period of sleep within 24 hours. Biphasic (or diphasic , bifurcated , or bimodal ) sleep refers to two periods, while polyphasic usually means more than two. [ 1 ]
Waking up earlier in the morning increases the response. [11]Shift work: nurses working on morning shifts with very early awakening (between 4:00–5:30 a.m.) had a greater and prolonged cortisol awakening response than those on the late day shift (between 6:00–9:00 a.m.) or the night shift (between 11:00 a.m.–2:00 p.m.). [12]
Reactive hypoglycemia, postprandial hypoglycemia, or sugar crash is a term describing recurrent episodes of symptomatic hypoglycemia occurring within four hours [1] after a high carbohydrate meal in people with and without diabetes. [2] The term is not necessarily a diagnosis since it requires an evaluation to determine the cause of the ...
[24] A feature that hypnagogia shares with other stages of sleep is amnesia . But this is a selective forgetfulness, affecting the hippocampal memory system, which is responsible for episodic or autobiographical memory , rather than the neocortical memory system, responsible for semantic memory . [ 6 ]
Occasional noncircadian days may occur (i.e., sleep is "skipped" for an entire day and night plus some portion of the following day), followed by a sleep period lasting 12 to 18 hours. The symptoms do not meet the criteria for any other sleep disorder causing inability to initiate sleep or excessive sleepiness.
Studies on rodents show that the response to neuronal injury due to acute sleep deprivation is adaptative before three hours of sleep loss per night and becomes maladaptative, and apoptosis occurs after. [35] Studies in mice show neuronal death (in the hippocampus, locus coeruleus, and medial PFC) occurs after two days of REM sleep deprivation.