Editing Sleep cycle (section)

{{short description|Oscillation between the slow-wave and REM phases of sleep}}
{{For|the album|Sleep Cycle}}
[[File:Hypro zyklus 1 en 103.svg|thumb|345px|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 sleep|slow-wave]] and [[rapid eye movement sleep|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 rhythm|circadian]] alternation between sleep and [[wakefulness]]. In humans, this cycle takes 70 to 110 minutes (90 ± 20 minutes).<ref>{{Cite web|title=What Happens During Sleep? {{!}} UPMC Sleep Medicine Resources|url=https://www.upmc.com/services/pulmonology/our-services/sleep-medicine/resources/during-sleep|access-date=2021-09-24|website=UPMC {{!}} Life Changing Medicine|language=en}}</ref>  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. <ref>{{Cite journal |url=https://publications.aap.org/pediatrics/article/43/1/65/44911/SLEEP-CYCLE-CHARACTERISTICS-IN-INFANTS?autologincheck=redirected |access-date=2023-11-18 |journal=Pediatrics |doi=10.1542/peds.43.1.65 |title=Sleep Cycle Characteristics in Infants |date=1969 |last1=Stern |first1=Evelyn |last2=Parmelee |first2=Arthur H. |last3=Akiyama |first3=Yoshio |last4=Schultz |first4=Marvin A. |last5=Wenner |first5=Waldemar H. |volume=43 |pages=65–70 |url-access=subscription }}</ref>