Journal of Sleep Disorders: Treatment and CareISSN: 2325-9639

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Opinion Article, J Sleep Disor Treat Care Vol: 12 Issue: 1

The Internal Mechanisms of Sleep and Awakening

Oleg Stalder*

Department of Neurosurgery, University of Amsterdam, Meibergdreef, Amsterdam, The Netherlands

*Corresponding Author: Oleg Stalder
Department of Neurosurgery, University of Amsterdam, Meibergdreef, Amsterdam, The Netherlands

Received date: 07 February, 2023, Manuscript No. JSDTC-23-96141;

Editor assigned date: 10 February, 2023, PreQC No. JSDTC-23-96141 (PQ);

Reviewed date: 24 February, 2023, QC No. JSDTC-23-96141;

Revised date: 03 March, 2023, Manuscript No. JSDTC-23-96141 (R);

Published date: 10 March, 2023, DOI: 10.4172/2325-9639.23.12.109

Citation: Stalder O (2023) The Internal Mechanisms of Sleep and Awakening. J Sleep Disor Treat Care 12:1.


Sleep and awakening are fundamental physiological processes that play vital roles in maintaining overall health and well-being. The internal mechanisms that govern these states are complex and involve intricate interactions between various physiological systems in the body.

Stages of sleep

Sleep is a dynamic process with distinct stages, including Rapid Eye Movement (REM) sleep and Non-Rapid Eye Movement (NREM) sleep, which is divided into three stages: N1, N2, and N3, each characterized by unique physiological and brainwave patterns.

N1 (Stage 1): N1 sleep is the lightest stage of sleep that occurs during the transition from wakefulness to sleep, characterized by slow eye movements, reduced muscle tone, and decreased brainwave activity. It may involve fleeting or fragmented thoughts and muscle jerks or twitches.

N2 (Stage 2): N2 sleep is a deeper stage of sleep marked by sleep spindles and K-complexes on the EEG, which are believed to be involved in memory consolidation and information processing. Sleep spindles are short bursts of high-frequency brainwave activity, while K-complexes are large, slow waves.

N3 (Stage 3): N3 sleep, also known as Slow-Wave Sleep (SWS) or delta sleep, is the deepest stage of sleep characterized by slow delta waves on the EEG, and is essential for physical restoration and growth, including tissue repair, hormone regulation, and immune system modulation.

Role of the circadian rhythm

The circadian rhythm, a 24-hour internal biological clock regulated by the Suprachiasmatic Nucleus (SCN) in the brain, influences the timing of sleep and awakening, and is synchronized by external cues, such as light and darkness, received by the eyes.

Melatonin: Melatonin, synthesized and released by the pineal gland in response to darkness, plays a vital role in circadian rhythm regulation and sleeps promotion, with increased levels during the evening and peak levels at night, promoting sleepiness and facilitating sleep onset.

Cortisol: Cortisol, a diurnally regulated stress hormone, promotes wakefulness and alertness during the day with high levels in the morning and gradually declining in the evening, preparing the body for sleep.

Neurochemical and neurophysiological processes during sleep and awakening

The internal mechanisms of sleep and awakening also involve complex neurochemical and neurophysiological processes that are regulated by various neurotransmitters, hormones, and brain regions.

Neurotransmitters: Neurotransmitter levels and activity, including serotonin, norepinephrine, dopamine, and acetylcholine, fluctuate during sleep and awakening, with serotonin and norepinephrine maintaining wakefulness, and dopamine and acetylcholine promoting REM sleep and regulating sleep stage transitions.

Sleep homeostasis: Sleep homeostasis, also known as “sleep debt” or “sleep pressure,” is the process by which the body regulates sleep amount and intensity based on prior wakefulness, with adenosine, a neurotransmitter that accumulates during wakefulness, playing a key role in promoting sleepiness and the need for sleep.

Brain regions: The hypothalamus (specifically the Ventrolateral Preoptic nucleus (VLPO)) is known as the “sleep-promoting center,” releasing inhibitory neurotransmitters, while the brainstem (specifically the Reticular Activating System (RAS)) promotes wakefulness through excitatory neurotransmitters.

REM sleep regulation: The regulation of REM sleep involves complex interactions between neurotransmitters like serotonin, acetylcholine, and norepinephrine, where acetylcholine promotes REM sleep while serotonin and norepinephrine inhibit it, helping regulate the duration and intensity of REM sleep.


The internal mechanisms of sleep and awakening are intricate and involve complex interactions between various physiological systems in the body. The stages of sleep, the role of the circadian rhythm, and the neurochemical and neurophysiological processes during sleep and awakening all play vital role in maintaining a healthy sleep-wake cycle.

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