Sleep cycle

Sample hypnogram showing one sleep cycle (the first of the night) from NREM through REM

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] Within the sleep of adults and infants there are cyclic fluctuations between quiet and active sleep. These fluctuations may persist during wakefulness as rest-activity cycles but are less easily discerned. [2]

  1. ^ "What Happens During Sleep? | UPMC Sleep Medicine Resources". UPMC | Life Changing Medicine. Retrieved 2021-09-24.
  2. ^ Stern, Evelyn; Parmelee, Arthur H.; Akiyama, Yoshio; Schultz, Marvin A.; Wenner, Waldemar H. (1969). "Sleep Cycle Characteristics in Infants". Pediatrics. 43: 65–70. doi:10.1542/peds.43.1.65. Retrieved 2023-11-18.

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