How do people study all night long

What happens in my body while I sleep?

Those who go to sleep go to sleep. But even in the deepest relaxation, the inactivity of the body is an illusion. Sleep is a very complex interplay of vital body functions without which humans cannot survive. It is amazing what our body can do while we are slumbering towards a new day.

The sleep phase

Many people find it difficult to fall asleep when it is too bright in the room. There is a reason for this: it is only when it gets dark that the pineal gland is stimulated to produce sufficient melatonin. By the way, this hormone unfolds its sleep-inducing effect not only at night, but also when there is a lack of light on dark winter days.

An increased melatonin concentration in the blood gives the body the signal to prepare for sleep. Now all systems switch to relaxation: the heart rate drops, blood pressure and body temperature drop. Breathing becomes shallower and very regular. The muscles also relax.

Our sleep has a rhythm

Anyone who believes that sleep is a uniform state is wrong. Rather, the organism goes through different phases of sleep, which are repeated several times over the course of the night. The deep sleep or NON-REM phase alternates with the dream or REM phase.

After falling asleep, the body and consciousness first sink into the first deep sleep, after which the first REM phase begins. The abbreviation REM stands for Rapid Eye Movement and describes the sleep interval in which we dream. Outwardly, this phase can be easily recognized by its eponymous phenomenon: the eyeballs move quickly back and forth under the closed lids. Other signs include irregular breathing and a fluctuating heart rate. Blood pressure rises and blood flow to the brain increases. In this phase, the brain processes and evaluates the experiences of the day. The body now immobilizes the most important muscle groups so that the often very intense dreams are not lived out in a motorized manner.

The first REM phase only lasts about ten minutes and then moves on to the next NON-REM phase. As the night progresses, however, the REM phases become longer and longer until the last one lasts for about an hour.

Which senses are active during sleep?

Even if we rarely need them during sleep: All five senses remain active throughout the night and are constantly on the receiving end. The incoming stimuli are filtered in the brain so that they do not disturb our night's sleep. The thalamus is responsible for this and is not called the gateway to consciousness for nothing. If extremely strong or very unfamiliar stimuli arrive here, the thalamus lets them through so that they penetrate consciousness - and the sleeper wakes up.

But the thalamus can do even more: If familiar stimuli are suddenly missing, the brain also gives an alarm and wakes the sleeper with it. So if you normally spend the night close to a busy street, you shouldn't be surprised when the lack of traffic noise leads to a restless sleep on holiday.

Young parents in particular are certainly very familiar with wet nurse sleep. Here every quiet whimper of the beloved offspring penetrates the consciousness immediately, and father or mother is suddenly wide awake. The reason is quickly explained: If the sensory impressions are linked to intense emotions, the stimulus threshold is extremely low. These noises are then perceived correspondingly easily.

Learn in your sleep?

And whether: The repeatedly recurring deep sleep phase uses the brain for memory formation. Biochemical changes initiate important cognitive processes, what has been learned and experienced is transferred to long-term memory. Studies have shown that people with disturbed deep sleep have a greatly reduced ability to learn and remember. Learning in your sleep is by no means just wishful thinking - if you get enough sleep after your lessons, you can both remember new information more easily and access it better.

Time for the hormones

While we sleep, our bodies release vital hormones that perform numerous functions in the body.

During the night, the level of the stress hormone cortisol falls - it does not rise again until the early hours of the morning. A lot of renin, which controls kidney function, is also released, especially shortly after falling asleep. The growth hormones also begin their work: tissue is repaired, body cells regenerate. They also regulate bone growth and muscle building, which is what makes getting enough sleep so important, especially for children.

Sleep for a strong immune system

The body's defenses are closely related to the quality and duration of sleep. That is why the need for sleep increases even with mild infections. It is to blame for messenger substances that make us tired so that natural defense cells can be formed during sleep and released in large numbers. In clinical studies, doctors have been able to show that sufficient sleep also promotes the formation of immune cells after a vaccination. The control group, which did not get enough sleep after the vaccination, had significantly fewer immune bodies in the blood.

Slim in your sleep?

Sufficient sleep is essential for digestion and metabolism. Only then does the body have the necessary rest for important digestive processes and can thus stabilize its fat balance.

The hormones leptin and ghrelin play a special role in this. While leptin is responsible for the feeling of satiety and increases energy consumption in higher concentrations, ghrelin controls appetite and causes hunger. Sleep disorders have been shown to reduce leptin secretion, while ghrelin production increases. As a result, we eat more food than we actually need. So if you don't get enough sleep, you will tend to be overweight in the long term.