If you watch a peacefully sleeping baby, you might get the feeling that not much happens in our body during sleep. But it is completely different - in the process of sleep, important processes take place in our body. These processes are related to different sleep phases that our body undergoes several times during the night. Roughly, a distinction is made between REM sleep (REM = Rapid Eye Movement) and non-REM sleep, which can be subdivided into light sleep and deep sleep again.
Different sleep phases
Depending on the duration of sleep, our body goes through the various sleep phases about four to six times a night - a sleep cycle takes about 90 minutes. During the first sleep cycle the deep sleep phase is particularly long, while the phase of REM sleep is only short. However, this changes during the night - the REM sleep phases continue to increase, the deep sleep phases on the other hand. To this day, however, it is unclear why our body goes through the individual sleep phases several times.
Non-REM sleep: fall asleep and sleep lightly
The first stage of non-REM sleep, falling asleep, takes only a few minutes for most people. It marks the transition from being awake to sleeping. The body relaxes and the brain slowly comes to rest. If the brain is so relaxed that it no longer perceives external stimuli such as light touches or soft noises, you have fallen asleep.
This first sleep phase is often characterized by the feeling of falling or restless movements of the legs. The twitching of the legs is due to the fact that the body functions are shut down at different speeds while sleeping: While the brain is almost "asleep", the muscles in the legs is still active. Stress can increase muscle twitching when falling asleep.
The feeling of falling, on the other hand, is due to another phenomenon: Lying in bed can lead to disturbances in the organ of balance in the ear - the result of these disturbances is the feeling that one falls.
Falling asleep is followed by the stage of light sleep. In this sleeping phase, the body relaxes even further, the breathing and the heartbeat slow down. The light sleep phase usually lasts between 30 and 60 minutes. Overall, it occupies more than 50 percent of total sleep.
Non-REM sleep: the deep sleep phase
Light sleep is followed by the deep sleep phase. It is the most relaxing sleep stage - during deep sleep, the body is motionless and completely relaxed. That is why it is very difficult to wake someone from the low blow. In the deep sleep phase, especially many growth hormones are released. Among other things, they play an important role in strengthening the immune system and in regenerating cell tissue. In addition, deep sleep should also be of special importance for learning.
The first deep sleep phase can take up to an hour, the other deep sleep phases during the night are shorter. After deep sleep, a light sleep phase is performed again before REM sleep begins. Interestingly, especially in the deep sleep phase, in which the body is actually completely relaxed, phenomena such as sleepwalking or talking while sleeping occur.
Therefore it is assumed that sleepwalking is not - as often assumed - the expression of dreams. Because only during the REM sleep phase do we dream intensively.
The REM sleep
REM sleep is characterized by rapid movements of the eyes under the closed eyelids. At this stage, the activities of our brain are similar to those of the waking state. Also pulse and respiration accelerate and the blood pressure rises. Through this activation, the calorie consumption in this sleep phase is almost identical to that of the wakefulness. It is thought that during REM sleep most of the information processing takes place in the brain.
The REM sleep phase is also characterized by frequent dreams. In order for us not to put our dreams into action, the musculature of our body is paralyzed at this time. From this fact probably results the uneasy feeling that probably everyone knows from his nightmares: One absolutely wants to run away, but can not move from the spot.
While the duration of the first REM sleep phase is only about ten minutes, the proportion of REM sleep continues to increase overnight: in the early morning, the REM sleep phase can be up to one hour. Overall, the proportion of REM sleep in total adult sleep accounts for just over 100 minutes per night. In newborn infants, on the other hand, sleep consists almost exclusively of REM sleep phases. Therefore, they are thought to have a special significance for the maturation of the central nervous system.