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The sleep cycle is an oscillation between the slow-wave and REM (paradoxical) phases of sleep. It is sometimes called the ultradian sleep cycle, sleep–dream cycle, or REM-NREM cycle, to distinguish it from the circadian alternation between sleep and wakefulness. In humans, this cycle takes 70 to 110 minutes (90 ± 20 minutes). [1]
The basic rest–activity cycle (BRAC) is a physiological arousal mechanism in humans proposed by Nathaniel Kleitman, [1] hypothesized to occur during both sleep and wakefulness. Empirically, it is an ultradian rhythm of approximately 90 minutes (80–120 minutes [ 2 ] ) characterized by different levels of excitement and rest.
Another study found that one night of sleep deprivation causes the hypermethylation of circadian clock genes–CLOCK and CRY1. [4] The circadian clock is a biochemical oscillator in organisms that is in sync with the 24 hour cycle of the Earth's rotation and has been found to impact gene expression and behavior. [ 5 ]
Known as slow-wave sleep or stage 3 non-REM sleep, this is the deepest stage of sleep and the hardest to wake up from. Brain activity slows down, muscles and bones strengthen, hormones regulate ...
Shop the best loud alarm clocks for heavy sleepers on Amazon and more that are recommended by our editor, who tested several of them, and a sleep psychologist. 7 Best Alarm Clocks for Heavy ...
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 ]
This ability to align behaviors such as feeding and activity to the external environmental cycle is a process called entrainment. [5] Biological rhythms, including cycles related to sleep and wakefulness, mood, and cognitive performance, are synchronized with the body's internal circadian clock. [6]
NREM Stage 1 (N1 – light sleep, somnolence, drowsy sleep – 5–10% of total sleep in adults): This is a stage of sleep that usually occurs between sleep and wakefulness, and sometimes occurs between periods of deeper sleep and periods of REM. The muscles are active, and the eyes roll slowly, opening and closing moderately.