Sleep cycle

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The sleep cycle is the oscillation between the slow wave and the sleep phase REM (paradox) phase, sometimes called the ultradian sleep cycle, the dream-sleep cycle, or the REM-NREM cycle, to distinguish it from the circadian turnover between sleep and awake. In humans this cycle takes 1-2 hours.

Video Sleep cycle

Characteristics

Electroencephalography is ready to show the sleep cycle time based on marked differences in brain waves manifested during REM and non-REM sleep. The delta wave activity, associated with deep slow wave sleep, typically shows regular oscillation throughout a restful night's sleep. The secretion of various hormones, including renin, growth hormone, and prolactin, is positively correlated with delta wave activity, while the secretion of the thyroid-stimulating hormone is inversely related. Heart rate variability, which is notably elevated during REM, may also be inversely correlated with the oscillation of delta waves over a 90-minute cycle.

Homeostatic functions, especially thermoregulation, occur normally during non-REM sleep, but not during REM sleep. Thus, during REM sleep, the body temperature tends to move away from the average level, and during non-REM sleep, to return to normal. Therefore, alternatives between these stages maintain the body temperature within an acceptable range.

In humans, the transition between non-REM and REM is sudden; in other animals, less so.

Researchers have proposed different models to explain the undoubted rhythm of complex electrochemical processes that result in the regular shifts of REM and NREM sleep. Monoamine is active during NREMS but not REMS, while acetylcholine is more active during REMS. The proposed reciprocal interaction model in 1970 suggested the granting and cyclic distribution between these two systems. Newer theories such as the "flip-flop" model proposed in the 2000s include a regulatory role in the inhibition of gamma-aminobutyric acid (GABA) neurotransmitters.

Maps Sleep cycle

Length

The standard rate given for the average length of the sleep cycle in adult men is 90 minutes. N1 (NREM stage 1) is when the person is drowsy or awake to fall asleep. Brain waves and muscle activity begin to decrease at this stage. N2 is when people experience light sleep. The eye movement has stopped now. The frequency of brain waves and muscle tone decreases. Heart rate and body temperature drop. N3 or even N4 is the most difficult stage to be awakened. Every part of the body is now relaxed, breathing, blood pressure and body temperature is reduced. The National Sleep Foundation discusses the various stages of NREM sleep and its importance. They describe REM sleep as "The unique state, where dreams usually occur, the brain is awake and the body is paralyzed." This unique stage is usually when the person is in the deepest sleep and dream stage. The 90 minute number for the average length of the sleep cycle was popularized by Nathaniel Kleitman around 1963. Other sources provide 90-110 minutes or 80-120 minutes.

In infants, the sleep cycle lasts about 50-60 minutes; average length increases as human beings grow up. In cats the sleep cycle lasts about 30 minutes, in mice about 12 minutes, and on elephants up to 120 minutes. (In this case the sleep cycle ontogeny appears to be proportional to the metabolic process, which varies in proportion to the size of the organism.However, the shorter sleep cycle detected in some elephants complicates this theory.)

Cycles can be defined as those that last from the end of one REM period to the end of the next, or from the beginning of REM, or from the beginning of the non-REM stage 2. (The decision on how to mark the period makes a difference for research purposes due to unavoidable inclusions or exceptions The first NREM of the night or its final REM phase if it directly precedes the resurrection.)

Sleeping 7-8 hours may include five cycles, two of which tend to be longer. REM takes more cycles as the night progresses.

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Awakening

Unplanned outbreaks occur most often during or after the REM sleep period, when body temperature increases.

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Continued when awake

Humans continued the 90-minute ultrara rhythm of 24 hours a day whether they were asleep or awake. During this cycle period associated with REM, people tend to daydream more and show less muscle tone. Kleitman and others who follow call this rhythm a basic break-cycle activity, in which the "sleep cycle" will be a manifestation. The difficulty for this theory is the fact that the long non-REM phase almost always precedes REM, regardless of when in a person's cycle it falls asleep.

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Changes

The sleep cycle proved resistant to systematic changes by drugs. Although some drugs shorten the REM period, they do not abolish the underlying rhythm. Involuntary REM recovery shortens the temporary cycle, as the brain moves into a more easily REM sleep ("REM rebound") in clear corrections for deprivation.

Michel Jouvet found that cats with forebrains omitted continued displaying REM-like characteristics on a 30-minute cycle, although never entering slower wave sleep.

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References

Bibliography

• Mallick, B. N.; S. R. Pandi-Perumal; Robert W. McCarley; and Adrian R. Morrison (2011). Rapid Eye Movement Sleep: Settings and Functions . Cambridge University Press. ISBN 978-0-521-11680-0
• Nir, and Tononi, "Dreaming and Brain: from Phenomenology to Neurophysiology." Cognitive Science Trends , vol. 14, no. 2, 2010, pp.Ã, 88-100.
• Varela, F., Engel, J., Wallace, B., & amp; Thupten Jinpa. (1997). Sleep, dreaming, and dying: Exploring consciousness with the Dalai Lama .

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