Sleep Stages - Sleep Phases

2023 Author: Wallace Forman | [email protected]. Last modified: 2023-05-24 12:25

Sleep & sleep stages

For many people, sleep means calm body and calm mind. But while we “slumber”, the brain is active, and various processes take place in the body that are important for processing events, regeneration, repair mechanisms and the immune system. The body adjusts the heat balance, muscles are tightened and relaxed, we move, shift our body position and much more.

We dream at night, even if we can often no longer remember it. We also wake up again and again during the night. This is normal to a certain extent - and often not remembered the next morning.

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So far, many processes related to sleep have been identified. However, much is still the subject of research. One thing is certain: everyone has to sleep. Good sleep helps reduce fatigue. Without sleep there is no healthy life and no productivity.

REM and NonREM sleep

Basically, two states can be recognized during sleep, which are very different from each other:

• REM sleep. It used to be called dream sleep. REM - Rapid Eye Movement - means something like short, rapid eye movements that can be observed at this stage. It is the time of the most intense dreams. In REM sleep, there are usually only minimal movements and high activity of the brain.
• NonREM sleep. This consists of different sleep stages (deep sleep, from light sleep to deep sleep). Movement sequences and brain activity are significantly reduced in NonREM sleep.

REM and NonREM sleep differ from what is known as the waking state, during which both movements and brain activity are high. In the course of sleep, the different states alternate again and again - in a relatively stable, characteristic sequence and in cycles of approx. 90 minutes. After falling asleep, it is above all a stage of NonREM sleep - the so-called deep sleep - that dominates the nocturnal "rest", in the morning the REM sleep.

The stages of sleep

Falling asleep and sleep are linked to many changes - such as those in brain activity. There are changes in almost all of the body's functional systems - for example, breathing and circulation, digestion, heat balance as well as hormone regulation and changes in muscle tone (muscle tension or relaxation), etc.

The body temperature drops somewhat during the night and is at its lowest level in the early morning. It increases again after about three o'clock at night. The pulse also usually drops at night. The blood pressure decreases compared to the activity during the day and increases again in the second half of the night.

Investigations in the sleep laboratory have shown that sleep is not a uniform process. Rather, different stages occur with different changes in the organism. The transition from wakefulness to sleep does not happen in one second. Ideally, we begin to relax before falling into deep sleep:

• "Sleep stage" (sleep stage I). This stage is a kind of transition from wakefulness to sleep. The consciousness is still active. It's easy to get startled. Brief, sudden twitches of the muscles may occur.
• Light sleep (sleep stage II). After about a quarter of an hour we usually fell asleep. The muscles relax. The consciousness is still partially active. You can be woken up relatively quickly. After a few minutes, deep sleep occurs.
• Deep sleep (early stage III and IV sleep). The muscles are relaxed, and breathing is slow and regular. The body uses deep sleep for regeneration, cell division, repairing tissue damage and repair mechanisms for damage to the genetic material. During this time there is growth in children and adolescents. As a rule, we are not so easily startled out of deep sleep - not even by louder noises.
• REM sleep stage (sleep stage R). In this phase the eyes move back and forth jerkily (Rapid Eye Movements) - hence the name. Except for the eyes and other facial muscles, the skeletal muscles are slack. However, the brain is active. Heartbeat and blood pressure are increased, breathing is fast and irregular, and the penis and vagina are well supplied with blood. REM sleep is the phase of dreams. We cannot always remember the content of dreams. See dreams for more information.

During the night, REM, deep sleep and light sleep alternate several times in different proportions and time intervals - until changes in the body (e.g. release of stress hormones and activation of the circulation) announce the end of sleep in the morning hours.