Sleep Cycle

A Sleep Cycle is a biological pattern that ...

• See: Wakefulness, Slow-Wave Sleep, Rapid Eye Movement Sleep, Sleep, Ultradian, Circadian Rhythm.

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References

2018

• (Wikipedia, 2018) ⇒ https://en.wikipedia.org/wiki/sleep_cycle Retrieved:2018-1-8.
  • The sleep cycle is an oscillation between the slow-wave and REM (paradoxical) phases of sleep, 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 1–2 hours.

2018b

• (Wikipedia, 2018) ⇒ https://en.wikipedia.org/wiki/sleep_cycle#Characteristics Retrieved:2018-1-8.
  • Electroencephalography readily shows the timing of sleep cycles by virtue of the marked distinction in brainwaves manifested during REM and non-REM sleep. Delta wave activity, correlating with slow-wave (deep) sleep, in particular shows regular oscillations throughout a good night’s sleep. Secretions of various hormones, including renin, growth hormone, and prolactin, correlate positively with delta-wave activity, while secretion of thyroid-stimulating hormone correlates inversely. Heart rate variability, well-known to increase during REM, predictably also correlates inversely with delta-wave oscillations over the ~90-minute cycle.

     Homeostatic functions, especially thermoregulation, occur normally during non-REM sleep, but not during REM sleep. Thus, during REM sleep, body temperature tends to drift away from its mean level, and during non-REM sleep, to return to normal. Alternation between the stages therefore maintains body temperature within an acceptable range. In humans the transition between non-REM and REM is abrupt; in animals, less so. Researchers have proposed different models to elucidate the undoubtedly complex rhythm of electrochemical processes that result in the regular alternation of REM and NREM sleep. Monoamines are active during NREMS but not REMS, whereas acetylcholine is more active during REMS. The reciprocal interaction model proposed in the 1970s suggested a cyclic give and take between these two systems. More recent theories such as the "flip-flop" model proposed in the 2000s include the regulatory role of in inhibitory neurotransmitter gamma-aminobutyric acid (GABA).

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