Sleep Cycle Characteristics:
– Electroencephalography distinguishes sleep cycles through brainwave patterns.
– Delta wave activity correlates with slow-wave sleep and hormonal secretions.
– Heart rate variability increases during REM and correlates inversely with delta-wave oscillations.
– EMG distinguishes sleep phases based on muscle tone.
– EOG measures eye movement and distinguishes REM sleep.
Sleep Cycle Length and Patterns:
– Average sleep cycle length in adults is 90 minutes.
– Sleep cycle stages include N1, N2, N3, and REM.
– Different sources suggest variations in sleep cycle length.
– Sleep cycle lengths vary across species, with infants having shorter cycles than adults.
– A 7-8 hour sleep typically includes five cycles, with REM taking up more time as the night progresses.
Awakening and Body Changes:
– Unprovoked awakenings commonly occur during or after REM sleep.
– Body temperature rises during REM sleep.
– Awakening patterns can be linked to specific stages of the sleep cycle.
Continuation and Alteration of Sleep Cycle:
– Humans exhibit a 90-minute ultradian rhythm throughout the day.
– Daydreaming and muscle tone change during the REM phase.
– The sleep cycle is considered a manifestation of the basic rest-activity cycle.
– Non-REM phases typically precede REM, regardless of sleep onset time.
– Sleep cycles are resistant to systematic alterations by drugs.
– Some drugs may shorten REM periods but do not eliminate the cycle.
– REM deprivation can temporarily shorten the sleep cycle.
– Methods to control sleep cycle alterations include managing light exposure, avoiding caffeine, and relaxation techniques.
Impact of External Factors on Sleep:
– Workaholism and intensive smartphone use impact the sleep-wake cycle.
– Compensating poor sleep with coffee affects vigilance and performance.
– External factors like work demands influence sleep patterns.
– Poor sleep quality can be compensated with certain stimulants.
– Lifestyle choices and work habits can disrupt the natural sleep cycle.
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). 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.