The 4 sleep phases
You want to understand what happens during sleep in your body? First, sleep can roughly be divided into two groups. The REM phase (rapid-eye-movement) and the non-REM phases, which in turn are divided into falling asleep, light sleep and deep sleep. Strictly speaking, no hour is the same in the night of the others and your body and mind do a wide variety of tasks. Within one night, your body goes through four different phases every 90 minutes, each of which is different.
1. Falling asleep
This sleep phase initially serves only as a transition between wakefulness and sleep. Your body prepares to sleep, blood pressure drops, breathing slows, and body temperature lowers. In short, your body starts to relax and you slowly slide to sleep.
2. Light sleep phase
The light sleep, as a sleep phase, you know certainly in the form of power nap. During a light sleep, you can quickly wake up to something. Nevertheless, your songs are tightly closed, your muscles relax and your blood pressure drops. The lower blood pressure protects your vessels and your heart. Sufficient sleep can significantly relieve your cardiovascular system and thus prevent diseases. During this sleep phase, you spend about 50% of the night. How much sleep can be achieved is shown by a study by Harvard University. It has been shown that short power drops can mean tremendous regeneration for the brain, optimizing concentration by 30%
3rd deep sleep phase
In deep sleep, as the third sleep phase, all your body functions are reduced to a minimum. You breathe flat, your heart is beating slowly and you have a lower body temperature. All this happens only to provide as much body power as possible for the various regeneration tasks. In the deep sleep phase, for example, particularly many growth hormones are released, which play an important role especially for the strengthening of the immune system, as well as for the regeneration of the cells. The deep sleep phase is also the most important for the brain. There new structures are stored in memory and the relevant information of the day is separated from the unimportant ones and stored. Learning while sleeping: no wishful thinking, but really true!
4th REM phase / dream phase
REM stands for “rapid eye movement”, which means “fast eye movement”. In this sleep phase, not only the movement of the eyes increases. The heartbeat, breathing, etc. are also increased again. But not only your body functions are activated, also in your brain happens more again. The Sleep Medicine Center in Munich found that the same brainwaves are active during the REM phase as they are in the waking state.² The REM phase is our subconscious processing mechanism of thoughts, feelings and fears. In this time you dream a lot. Therefore, this phase is often called dream sleep. In the REM phase, your imagination is also stimulated and the logical centers of the brain are turned off. This is how to explain your mostly confused and bizarre dreams.
The different phases are run through several times in one night. After 60 to 90 minutes, the REM sleep occurs again. In the deep sleep phase and the REM sleep phase, the actual physical recovery takes place. But when do we wake up? About 6 to 7 o’clock melatonin production stops when the sun rises slowly and a new day begins.
An increase in the stress hormone cortisol plays an important role here, is virtually the antagonist of melatonin. Of course, around 9 o’clock we have the highest cortisol and testosterone levels and are ready to start the day full of productivity. By sunlight we make vitamin D, which is responsible for the production of the happiness hormone serotonin. In the evening, serotonin is converted to melatonin. This creates the cycle of life and sleep.
— The Nobel Prize (@NobelPrize) October 2, 2017
Take-home message # 2: Good sleep means you have a high percentage of REM sleep and deep sleep periods in your sleep. Sleep consists of four phases that repeat several times in one night. The more often and longer you go through the deep and restful phases, the better your sleep.