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The processes that occur with a person during sleep

Процессы, которые происходят с человеком во время сна

Sleep (Latin somnus) is a natural physiological process of staying in a state with a minimum level of brain activity and a reduced response to the surrounding world, inherent in mammals, birds, fish and some other animals, including insects (for example, Drosophila). In addition, the word “dream” refers to a sequence of images (formed during the so-called “fast sleep” phase) that a person can remember (see also a dream). Physiologically, normal sleep differs from other states similar to it - suspended animation (the so-called "hibernation" in animals), hypnotic sleep, coma, fainting, lethargic sleep.

1. Body temperature drops

Процессы, которые происходят с человеком во время сна

Since most muscles become inactive during sleep, the body burns fewer calories than during the day, and body temperature drops. Scientists have found that body temperature is usually the lowest around 2:30 in the morning.

2. Eyes move

Процессы, которые происходят с человеком во время сна

Although eyes have been closed for centuries in a dream, they move beneath them. In fact, such a movement even varies depending on the specific stages of sleep.

3. The body twitches

Процессы, которые происходят с человеком во время сна

Sharp twitches and jerks are mainly associated with the first stage of sleep. They are generally harmless, but they can be strong enough to actually wake a person.

4. The muscles are relaxed

Процессы, которые происходят с человеком во время сна

There is a good reason why most muscles are relaxed during sleep. If they were active, then a person could move during sleep, which would be extremely dangerous.

5. The skin is restored

Процессы, которые происходят с человеком во время сна

The upper layer of the skin consists of tightly packed dead cells that are constantly discarded throughout the day. During sleep, the metabolic rate of the skin is accelerated and in many cells of the body an increase in activity and a decrease in protein breakdown begin. Since proteins are needed for growth and repair damage from factors such as ultraviolet radiation, deep sleep has beneficial effects on the skin.

6. The brain forgets useless information

Процессы, которые происходят с человеком во время сна

People perceive an insane amount of information throughout the day. If they remembered her all, they would soon have gone mad. That is why at night the brain sorts information and forgets about the unnecessary.

7. The throat narrows

Процессы, которые происходят с человеком во время сна

Unlike most other muscles, the throat muscles do not paralyze during sleep, as they are necessary to breathe. However, they relax during sleep, causing the throat to contract. It can also cause snoring.

8. The body produces hormones

Процессы, которые происходят с человеком во время сна

During the slow sleep stage, the human body produces hormones that stimulate the growth, reproduction of cells and cell regeneration. It is an important regulator of the immune system.

9. The immune system is at a record high.

Процессы, которые происходят с человеком во время сна

It has been proven that sleep deprivation negatively affects the immune system. One study found that people who got the flu shot and were sleep deprived the next night did not produce the antibodies they needed to protect them from the flu. Therefore, if a person has noticed the first signs of infection, he should sleep.

10. Weight Loss

Процессы, которые происходят с человеком во время сна

During sleep, a person loses water by sweating and exhaling moist air. It also occurs throughout the day, but eating and drinking negates any weight loss. Therefore, for any diet you need a good and long sleep.

11. Dry mouth

Процессы, которые происходят с человеком во время сна

Since saliva is mainly needed for food, and a person does not eat during sleep, the amount of saliva secreted decreases at night. Consequently, the mouth dries up, and in the morning often thirsty.

12. Teeth grinding

Процессы, которые происходят с человеком во время сна

According to research estimates, about 5% of people suffer from a bizarre condition known as bruxism. This results in excessive gnashing of teeth during sleep and can ultimately lead to tooth damage. Scientists are not sure what exactly causes this condition, but they believe that this may be a peculiar form of stress relief.

13. The body becomes longer

Процессы, которые происходят с человеком во время сна

It has been found that human growth can increase by several centimeters in the morning, compared to the evening. During sleep in a horizontal position, the spine straightens, because the weight of the body does not put pressure on it.

14. Blood pressure drops sharply

Процессы, которые происходят с человеком во время сна

During sleep, any person experiences a condition that is known as a "nightly drop in blood pressure." On average, it falls at night by 5 - 7 mm. Hg. Art.

15. Sleepwalking

Процессы, которые происходят с человеком во время сна

From a scientific point of view, disorders known as parasomnia (sleepwalking and other activities during sleep) include the behavior, emotions, sensations and dreams that usually occur during transitions between some of the stages of sleep. Parasomnias are mostly harmless, but there have been cases when people were injured during sleepwalking.

16. Sexual arousal

Процессы, которые происходят с человеком во время сна

Both men and women can be aroused during sleep. When the brain is more active during sleep, it requires more oxygen. As a result, the flow of blood throughout the body increases, which leads to swelling of the genitals.

17. Dreams

Процессы, которые происходят с человеком во время сна

The content and purpose of dreams is not fully understood, but it is known that an ordinary person has 3 to 5 dreams per night. Dreams mainly occur in the first stage of sleep, when the human brain is most active. However, most dreams are immediately or quickly forgotten.

18. The brain makes decisions

Процессы, которые происходят с человеком во время сна

A recent study showed that the brain can process information and prepare for further action during sleep, effectively making decisions in an unconscious state. In fact, the brain can even make important discoveries during sleep.

19. Flatulence

Процессы, которые происходят с человеком во время сна

The muscles of the anal sphincter slightly weaken during sleep, which facilitates the release of gases from the intestines. The good news is that the sense of smell also weakens during sleep.

20. Removal of toxins

Процессы, которые происходят с человеком во время сна

Getting rid of toxins allows the body and brain to regain strength. In people who sleep poorly, filtering harmful substances is not so effective, so experts say: this is what leads to the fact that people suffering from insomnia are a little crazy.

21. Unconscious awakening

Процессы, которые происходят с человеком во время сна

Scientific studies have shown that people wake up many times during sleep, but these awakenings are so short that they do not remember them. Typically, these awakenings occur during transition periods between stages of sleep.

22. You can stop breathing

Процессы, которые происходят с человеком во время сна

Millions of people around the world are suffering from a sleep disorder known as "apnea." The disorder is characterized by pauses between breaths while breathing, and each pause can last for several seconds or even several minutes.

23. You can hear the explosion

Процессы, которые происходят с человеком во время сна

“Exploding head syndrome” is a rare condition in which a person hears loud imaginary sounds (such as a bomb explosion, the sound of a gunshot, etc.) or experiences a strange feeling of an explosion when he falls asleep or wakes up. It is painless, but it scares the sufferer.

24. Talking during sleep

Процессы, которые происходят с человеком во время сна

Talking during sleep is a parasomnia in which a person begins to talk uncontrollably out loud during sleep. Such “conversations” can be quite loud and can be either simple muttering sounds or long, often slurred speeches.

Physiology of sleep

Процессы, которые происходят с человеком во время сна

In a dream, the level of anabolic processes rises and catabolism decreases. Sleep normally occurs cyclically, approximately every 24 hours. These cycles are called circadian rhythms. They are redefined every day, the most important factor is the level of lighting. The concentration level of special photo-dependent proteins depends on the natural cycle of illumination. The circadian cycle is usually set to daylight hours. In addition to night sleep, in some cultures there is a physiologically determined short-term daytime sleep - siesta.

Falling asleep

Immediately before bedtime, a state of drowsiness occurs, a decrease in brain activity, characterized by:

  1. decreased level of consciousness;
  2. yawning
  3. lowering the sensitivity of sensory systems;
  4. a decrease in heart rate, a decrease in the secretory activity of glands (salivary - dry mouth, lacrimal - burning eyes, clumping of the eyelids).

Professor Richard R. Budzin has been studying sleep disorders for many years at the University of Arizona's Sleep Research Laboratory and recommends a six-step quick fall asleep technique. In an annual report on clinical psychology, he described various psychological approaches that were used to treat insomnia (Bootzin & Epstein, 2011). Such treatment was previously called stimulus control treatment (Morin et al., 2006). Tips include: go to bed only when you want to sleep, use the bed only for sleeping, do not lie in bed for more than 10 minutes, if you can’t fall asleep - make the bed associated only with falling asleep quickly, waking up in the morning with one and same time, do not sleep during the day.

Sleep pattern

Sleep is a special state of consciousness of humans and animals, which includes a number of stages that regularly recur during the night (with a normal daily schedule). The appearance of these stages is due to the activity of various brain structures.

In a healthy person, sleep begins with the first stage of slow sleep (Non-REM sleep), which lasts 5-10 minutes. Then comes the 2nd stage, which lasts about 20 minutes. Another 30-45 minutes falls on the period of 3-4 stages. After this, the sleeper returns to the 2nd stage of slow sleep, after which the first episode of REM sleep occurs, which has a short duration of about 5 minutes. This whole sequence is called a cycle. The first cycle has a duration of 90-100 minutes. Then the cycles are repeated, while the proportion of slow sleep decreases, and the proportion of REM sleep (REM sleep) gradually increases, the last episode of which in some cases can reach 1 hour. On average, with a full healthy sleep, five full cycles are observed. It is convenient to present the sequence of stage changes and their duration in the form of a hypnogram, which visually displays the patient’s sleep structure.

Slow sleep

Slow sleep (syn: slow wave sleep, orthodox sleep), lasts 80-90 minutes. It comes immediately after falling asleep.

  • First stage. The alpha rhythm decreases, and low-amplitude slow theta rhythms appear, in amplitude equal to or greater than the alpha rhythm. Behavior: nap with half-asleep dreams, absurd or hallucinogenic thoughts and sometimes with hypnagogic images (like hallucinations). Muscle activity decreases, the frequency of respiration and pulse decreases, the metabolism slows down, and the temperature decreases, the eyes can make slow movements. At this stage, ideas can appear intuitively that contribute to the successful solution of a particular problem or the illusion of their existence. In the EEG, acute vertex waves, POSTS can be recorded, hypnagogic hypersynchrony is occasionally observed. Hypnagogic twitching may occur at this stage.
  • Second stage. (shallow or light sleep). A further decrease in tonic muscle activity. Heart rate slows down, body temperature decreases, eyes are motionless. Takes about 45-55% of the total sleep time. The first episode of the second stage lasts about 20 minutes. Theta waves dominate in the EEG, the so-called "sleep spindles" appear - the sigma rhythm, which is a rapid alpha rhythm (12-14-20 Hz). With the advent of “sleepy spindles”, consciousness is turned off; in the pauses between the spindles (and they occur about 2-5 times per minute) a person is easy to wake. Occasionally, sleepy spindles can be included in the structure of stages 3-4. Thresholds of perception increase.
  • Third stage. Slow sleep. Stage is classified as 3rd if delta oscillations (2 Hz) occupy less than 50% and 4th stage if delta is more than 50%.
  • The fourth stage. The deepest slowest delta sleep. Delta oscillations (2 Hz) predominate. The third and fourth stages are often combined under the name delta sleep. It is very difficult to wake a person at this time; 80% of dreams arise, and it is at this stage that sleepwalking attacks, nightly horrors, conversations in sleep and enuresis in children are possible. However, a person remembers almost none of this.

In a healthy person, the third stage takes 5-8%, and the fourth stage is about 10-15% of the total sleep time. The first four slow-wave stages of sleep normally occupy 75-80% of the entire sleep period. It is believed that slow sleep is associated with the restoration of energy consumption. Studies have shown that it is the phase of slow sleep that is key to reinforcing conscious “declarative” memories.

Fast sleep

REM sleep (synonym: REM sleep, paradoxical sleep, the stage of rapid eye movements, or abbreviated BDG sleep, REM sleep). This is the fifth stage of sleep; it was discovered in 1953 by Kleitman and his graduate student Aserinsky. A fast sleep follows a slow one and lasts 10-15 minutes.

On the EEG, fast fluctuations in electrical activity are observed, close in value to the beta-waves of the sawtooth wave. During this period, the electrical activity of the brain is similar to the state of wakefulness. At the same time (and this is paradoxical) in this stage a person is completely still, due to a sharp drop in muscle tone. However, eyeballs very often and periodically make quick movements under closed eyelids. There is a clear link between BDG and dreams. If you wake the sleeping man at this time, then in 90% of cases you can hear a story about a vivid dream.

The electroencephalogram reflects the state of activation and is more like an EEG of the 1st stage of sleep. The first episode of REM sleep occurs in 70-90 minutes from the moment of falling asleep, lasts 5-10 minutes. In the course of sleep, the duration of subsequent episodes of BDG sleep increases, reaching several tens of minutes in the morning. In an adult, the proportion of the REM phase is about 20-25% of the total sleep time. The REM phase from cycle to cycle lengthens, and the depth of sleep decreases. Part of the interrupted REM sleep should be replenished in the following cycles.

It is believed that REM provides psychological defense functions, information processing, its exchange between consciousness and the subconscious.


During REM sleep, there is an increase in the secretion of adrenal hormones, increased cerebral blood flow, a change in heart rate, various forms of arrhythmias, rises and drops in blood pressure, changes in breathing patterns, an erection of the penis or clitoris.

Sleep function

The visceral theory of sleep states that in a dream, the central nervous system analyzes and regulates the functioning of internal organs.

  • Sleep provides rest of the body.
  • Sleep contributes to the processing and storage of information. Sleep (especially slow) facilitates the consolidation of the studied material, fast sleep implements subconscious models of expected events.
  • Sleep is the adaptation of the body to changes in light (day-night).
  • Sleep restores immunity by activating T-lymphocytes fighting colds and viral diseases.

25. Lowering the pain threshold

Процессы, которые происходят с человеком во время сна

When the body is completely relaxed to the point of paralysis, the nerves cannot receive pain signals and transmit them to the brain. It also explains why people do not hear smells, sounds, etc. during sleep.

Required Sleep Time

The average duration of a person’s sleep usually depends on numerous factors: from age, gender, lifestyle, nutrition and degree of fatigue, to external factors (general noise level, location, etc.). In the general case, in case of sleep disturbances, its duration can be from several seconds to several days.

There are also cases that an adult needs 12 hours to get enough sleep or recover from hard work and sleepless nights. Duration of sleep less than 5 hours (hyposomnia) or a violation of the physiological structure are considered risk factors for insomnia.

Sleep deprivation is a very difficult test. For several days, the person’s consciousness loses clarity, he feels an irresistible desire to fall asleep, periodically “falls” into a borderline state with a confused consciousness. This method of psychological pressure is used during interrogations, and is considered as sophisticated torture.


Recent studies on the functionality of dreams at the University of Helsinki (prof. En: Pekka Sutola) have shown that the REM phase of sleep sometimes quickly occurs in mammals, and then they go into the phase of deep sleep. This explains why epileptics have a REM-like phase during an attack and are unable to recall events several hours before the attack. A fuller structure of the functioning of this system has not yet been established.

If we take 70 years for the average age, then of these, a person sleeps about 23 years.


Afternoon short-term sleep-rest - siesta - is a historical element of the culture of many peoples. Most often it is found in hot countries. A recent study conducted in Greece jointly by the University of Athens Medical School and Harvard showed that a half-hour afternoon nap, at least three times a week, reduces the risk of death from a heart attack by 37%.

Sleep pathology

With persistent sleep disorders, there are situations where the intervention of a doctor is necessary. In the news media published several cases of long-term complete lack of sleep in humans.

  • Dysomnia - disturbances of night sleep, for example, insomnia (insomnia). Causes: neurosis, psychosis, organic brain damage (encephalitis, epilepsy), somatic diseases.
  • Sleep apnea - psychogenic or mechanical respiratory failure in a dream.
  • Hypersomnia is an irresistible pathological drowsiness. Examples: narcolepsy, lethargic sleep.
  • Parasomnia - reason: neurosis. Examples: somnambulism (sleepwalking / sleepwalking), gnashing of teeth, nightmares, epileptic seizures, etc.
  • Carotid palsy is a condition where muscle paralysis occurs before falling asleep or after waking up.