Sleep doesn’t automatically mean that body and mind „are sleeping“. Our brain is very active during sleep and several important processes take place: processing of events, regeneration as well as repair mechanisms and strengthening of the immune System.
Although we often can’t remember it, our sleep is accompanied by dreams. And, on an average we wake up about 30 times per night, mostly unnoticed. Only when we are awake for more than three minutes, we remember it in the morning.
Healthy sleep decreases fatigue and is important for our performance as well as our well-being.
REM- and non-REM-sleep
Sleep consists of two totally different conditions.
During REM-sleep short and rapid eye-movements take place. In this condition there are the most intense dreams. Only few movements take place and the brain is very active.
Non-REM-sleep consists of different sleep stages. Here, clearly less movements take place. The brain-activity is decreased.
These two stages differ from the so-called waking-stage. During waking-stage motion-sequences and brain activity are high. During night, about every 90 minutes and in a quite evenly chronology a constant alternation of REM- and non-REM-sleep take place.
After falling asleep we mainly are in non-REM-sleep (deep sleep) which prevails most of the night. The closer morning comes, the more time we spend in REM-sleep.
When falling asleep and while sleeping most functional systems of our body are changing, like digestion, heat balance, hormone regulation, breathing, circulatory and muscular tone.
Examinations in sleep laboratory revealed that sleep consists of different stages which are accompanied by the different physical changes.
- Falling asleep
Here, the change from wake-stage to sleep takes place. The conscious is still active and during this stage, muscle twitches might occur. Also, startling is easy. This stage takes about 10 % of our night.
- Light sleep
After about 15 minutes we pass from falling asleep to light sleep. Here, the musculature relaxes but conscious is still partly active. During light sleep we are woken easily. This stages takes about 50 % of total sleeping time.
- Deep sleep
In this stage we are sound asleep. Heartbeat, breathing and blood pressure decrease, the muscles are relaxed. During deep sleep our body recovers, cell division occurs. With children and adolescents growth is happening during deep sleep. In this stage we are not woken easily, not even by loud noises. A grown-up spends about 20 % of the night in deep sleep.
During REM-sleep we are moving the eyes rapidly. Heartbeat and breathing increase and are irregular. Our brain is working actively. In this stage, dreams occur. But, when we wake up we are not always able to remember the dreams. Grown-ups spend about 20 % in this stage, infants and small children a lot more.
In the course of the night, the share of the single sleeping stages alternates. The closer the morning comes our physical processes stimulate circulatory as well as release of stress hormones which signals the forthcoming end of sleep.
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