What happens when you sleep?

We spend about a third of our lives asleep. This alone shows that sleep plays a central role in our lives. And not without reason: sleep has many functions that are essential for a healthy everyday life. Find out here what exactly happens during sleep and how you can get the most out of it.

Table of contents

      1. Active sleep
      2. Sleep phases at a glance
      3. What happens during sleep
      4. Sleep - the central recovery period
      5. Conclusion

      Active sleep

      Sleep = doing nothing? Wrong! Numerous essential processes take place during sleep, because sleep is the central regeneration period for our body and especially for our brain. For a long time it was assumed that our brain is less active during sleep - in fact it is only active in a different way. During the day it continuously processes information and these processes require a lot of energy. Although the brain only takes up about 2% of our body volume, it consumes about 20% of the total energy. When we rest and close our eyes, the activity of our nerve cells (neurons) reduces and energy consumption slowly decreases.

      During the night, we then go through several sleep cycles, which in turn are divided into different sleep phases. A cycle lasts about 90 to 110 minutes and is run through several times per night. The first two sleep cycles are particularly important for brain recovery. This is why they are also called core sleep.

      Sleep phases at a glance

      After a short phase of falling asleep, we usually fall into a light sleep stage. Then our muscles relax, pulse and breathing become more regular and body temperature drops.

      This superficial sleep, in which we spend just under half of our sleeping time, is then followed by deep sleep. It dominates the first third of the night and ensures that our body shuts down even further, heartbeat and breathing slow down and blood pressure drops. Especially in deep sleep, when nerve activity is significantly reduced, the energy stores in our brain can recharge. At the same time, numerous hormones and messenger substances are released that control and support metabolic and regeneration processes.

      Schlafzyklus: Schlafphasen

      Following deep sleep, we then slide into the dream sleep phases, also known as REM phases, in which our brain processes and evaluates the experiences of the day. REM stands for "Rapid Eye Movement" because during these sleep periods, we dream while rapidly moving our eyes back and forth under our closed eyelids. For this to work, blood flow to the brain increases, blood pressure rises, and our heart rate and breathing also become more irregular.

      Core sleep, the first two sleep cycles, is particularly important for our regeneration. But what actually happens in our body while we sleep?

      What happens during sleep

      Learning and memory processes

      At work, at school or during leisure time - our brain takes in information everywhere, both consciously and unconsciously. During sleep, these impressions are stored, processed, ordered or deleted by the brain and pass from short-term memory to long-term memory. In this way, relevant information is stored in the long term and made ready for retrieval, and unimportant information is deleted so that we are receptive again for the next day after sleep. Sleep thus plays a central role in our ability to learn. You can find out more about learning while asleep in article.

      Strengthening the immune system

      During sleep, the number of natural defense cells in the body increases and our immune system works at full speed to protect us from viruses, bacteria and other pathogens. "The immune system is directly related to the length and quality of our sleep." says sleep researcher and smartsleep® founder Dr. Markus Dworak. So if you get enough sleep, you reduce the likelihood of getting sick and give your body time to strengthen its defences.

      Cell renewal

      Schöne Haut, Haare, Nägel: Zellerneuerung im Schlaf

      Our hormone balance is also active while we sleep. Important growth hormones are released, which are involved in almost all functions in our body. For example, they control enzyme production and cell renewal, help to build and repair tissue and support the regeneration of our body cells. Sleep is especially essential for maintaining healthy skin, hair, nails and connective tissue, making it an important foundation for a healthy and beautiful appearance. How exactly sleep makes us beautiful, you can read .

      Optimization of the metabolism

      During the night the body has the necessary rest for important metabolic and digestive processes. Metabolic products, such as uric acid, are broken down to a greater extent and the fat metabolism is also active in order to provide energy for regeneration.

      Sleep - the central recovery period

      Sleep is essential for our body and our mind in many ways. While the conscious mind rests at night, the brain is by no means idle - it processes , sorts and stores the information and impressions of the day. And our body also needs sleep to repair body cells, regulate hormone balance and metabolism, and strengthen the immune system. These are numerous tasks that are fundamental to our health and show us how important a healthy sleep pattern and enough sleep really are.


      • At night we go through several sleep cycles, which are divided into falling asleep, light sleep, deep sleep and dream or REM sleep phases.
      • Learning and memory processes take place during sleep, processing, organizing and storing information and impressions of the day.
      • Growth hormones are released during sleep, which support cell renewal and regeneration and thus promote healthy skin, hair and nails.
      • Metabolism is regulated and optimised during sleep
      • The number of defence cells increases at night, strengthening the immune system during sleep

      Best regards and see you soon!

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