Runny nose

Why does a person need sleep? Why do we need sleep and how it changed with the advent of electricity

Poluektov Mikhail Guryevich, somnologist, candidate of medical sciences, associate professor of the First Moscow Medical University named after I.M. Sechenov

Until now, sleep seems to be a mysterious state, the nature of which is debated by physiologists, chemists, psychologists and other scientists. According to physiologists, who gained popularity back in the 19th century, sleep arises from the fact that in the evening “the blood drains from the head” - the brain cells do not have enough nutrition and they switch to inhibition mode. This theory, an active proponent of which was the French physiologist Mosso, was proven by experiment on a scale bed. When a person placed horizontally on this bed fell asleep, the head end of the bed rose. But as it turned out upon further observation, after some time of sleep, the blood, on the contrary, rushes to the head and the foot of the bed rises.

In 1937, Alfred Loomis and colleagues proposed the first classification of human sleep stages based on changes in the electroencephalogram. However, further development of neurophysiology has shown that to more accurately determine the stages of sleep, it is necessary to record more indicators than just electrical brain potentials. In 1953, American scientists Nathaniel Kleitman and Eugene Azerinsky discovered the last, fifth stage of sleep, called REM sleep. The establishment of clear criteria for sleep and wakefulness made it possible to determine how the physiological systems of the body - cardiovascular, nervous, respiratory, genitourinary and others - function during different periods of sleep. This made it possible to answer many questions regarding the purpose of sleep for the human body.

People could not come to an understanding of the nature of sleep for a very long time, since there were no methods for objectively recording the state of the body during sleep. This became possible only in the 20th century, when the German psychiatrist Hans Berger introduced the electroencephalography (EEG) method into clinical practice. Using this research method, electrical currents representing the potential difference between two electrodes were recorded from different areas of the skull. It turned out that during different periods of recording, especially when comparing sleep and wakefulness, the electroencephalogram pattern in the same person can differ significantly.

Psychological theories of sleep, especially Sigmund Freud's theory, refused to answer questions about what substance or action causes sleep. They believed that the need for sleep was programmed from the beginning, since a person from time to time must plunge into a state of freedom from the outside world, as was the case in the womb. At the same time, according to the psychologist, a person gets the opportunity to digest a large amount of heterogeneous information received during the day and restore mental balance.

The next popular theory of the origin of sleep was the theory of hypnotoxin - “sleeping poison”. French psychologists Legendre and Pieron suggested that the increased tendency to fall asleep in the evening may be associated with the accumulation of a certain substance in the human body during wakefulness - hypnotoxin. When a person falls asleep, this “sleepy poison” begins to be neutralized and by the time of waking up in the morning it disappears from the body almost completely. Scientists conducted experiments on dogs that were not allowed to sleep - when they died, they actually found changes in their brains similar to damage caused by poisoning. Moreover, if a well-rested dog was transfused with blood from a sleep-deprived one, the first dog began to show signs of sleepy behavior and fell asleep. However, despite titanic attempts to isolate the “dream substance,” no one has yet succeeded in doing so.

What is sleep?

So, what is a human dream? How does the transition from wakefulness to sleep usually occur? Usually in the evening a person begins to feel tired, notes a decrease in energy, mental activity worsens, and emotions become dull. This becomes a signal that it is time to go to the bedroom. A person lies down on the bed, turns off the light and relaxes. After some time, his awareness of his surroundings begins to “fade”, dream-like sensations appear, after which voluntary consciousness “turns off” until he wakes up in the morning or at night.

If you observe this person using a special device - a polysomnograph, the researcher can see how, during the transition from wakefulness to sleep, the electrical picture of the brain changes - fast and organized electrical potentials are replaced by scattered slower electrical activity. At this time, you can also observe slow, floating movements of the eyeballs. This is the first stage of sleep. It takes a short period of time - usually 5-10 minutes per night.

The first stage is replaced by the second stage of sleep. It is quite easy to determine from the picture of the electroencephalogram, since at this time specific phenomena can be observed: complexes with several peaks and troughs and very specific periods of rapid electrical activity - sleep spindles. The second stage usually takes up the largest portion of sleep time - about 50%.

With further deepening of sleep, the second stage passes into the 3rd and 4th stages - the so-called delta sleep. During this period of sleep, a large number of slow, high-amplitude electrical potentials are detected on the electroencephalogram. Delta sleep usually takes up about 20% of sleep time and ends the so-called “slow sleep” - a part of sleep that is characterized by slow electrical activity that is unusual for the waking state.

This is usually followed by REM sleep, which takes up 20-25% of total sleep. It is impossible to determine REM sleep from just one electroencephalogram. This is due to the fact that the bioelectrical pattern of REM sleep is very similar to the pattern of wakefulness. However, if you observe a person in a state of REM sleep, it becomes clear that he is sleeping - his eyes are closed, the sleeper does not react in any way to sounds or touches. In this case, one may notice occasional twitching of the arms or legs and sharp, rapid movements of the eyeballs under uncovered eyelids. Based on the name of this phenomenon, this part of sleep is called REM sleep. If you wake up a person at this time, then most often (about 80% of cases) he will tell you that he had a dream - or rather, a dream. The body is protected from active actions during a dream (when in a dream a person can run, fight, scream, etc.) by turning off the tone of the striated muscles during this period.

The stages of sleep alternate in a certain order, forming the so-called sleep cycle - first they go through four stages of slow-wave sleep, and the cycle ends with rapid sleep. During a night's sleep, 4-6 sleep cycles are usually repeated. The duration of such a cycle in an adult is 90 minutes, in children - about 60 minutes. The pattern of alternation of sleep stages is not strictly observed. Periodically during sleep, a person may be awakened (transition to a more superficial stage of sleep for a while) due to a sharp sound or feeling discomfort, or even wake up and go to the toilet, but still, after some time, the sleep cycle ends and is replaced by a new one.

Another important sleep pattern is the varying ratio of slow-wave sleep to REM sleep in the cycle, changing as the night progresses. Professor Theodor Steckmann promoted the thesis that “one hour of sleep before midnight is equal to two hours after.” Indeed, in the first hours after falling asleep, it is usually more difficult to wake a person than in the morning. This is due to the fact that in the first half of sleep, slow-wave sleep predominates, in the second - fast sleep. This is why we remember dreams more often if we wake up in the morning rather than in the middle of the night. At the same time, the overall restorative effect is greater with slow-wave sleep, so after sleeping for a few hours at the beginning of the night, we can feel almost restored from daytime wakefulness.

Why do you need sleep?

The purpose of slow and fast sleep has been clarified on the basis of numerous experiments based on mental and physical stress or deprivation of one or another part of sleep. It has been shown that physical activity, especially carried out in the evening, leads to an increase in the amount of slow-wave sleep, mainly its deepest stages (3rd and 4th). The use of mental stress leads to an increase in the number of deep stages of slow-wave sleep and an acceleration of the onset of REM sleep. Biochemical studies have shown that 80% of the daily amount of growth hormone (somatotropic hormone) is released during deep slow-wave sleep. And with some sleep disorders, when the amount of deep slow-wave sleep decreases, for example, with obstructive sleep apnea syndrome, children experience delayed growth and weight gain. Thus, it is believed that slow-wave sleep, especially its deep stages, are most responsible for the physical restoration of the human body.

The role of REM sleep was determined in ingenious experiments by depriving this part of sleep, carried out on rats. The animal was placed on a platform floating in the water, on which it could only stay on by actively balancing. When falling asleep and going into REM sleep, a decrease in muscle tone occurred - the animal lost the ability to stay on the platform, fell into the water and immediately woke up. In this way, it was possible to significantly limit the amount of REM sleep the rat received. Next, experiments were carried out on teaching animals to make their way through a maze to a feeding trough. It turned out that if a rat trained in this way was then deprived of REM sleep, it forgot the path to the desired bait. This experiment provided one of the clearest confirmations of the important role of REM sleep for remembering previous events in mammals.

In humans, experiments with deprivation of REM or slow-wave sleep have produced ambiguous results, which is due to the complexity of higher nervous activity and the formation of motivations. Most often, due to deprivation of REM sleep, the subjects became emotionally unstable, sometimes aggressive. Some experienced hallucinations. Summarizing the results of these experiments, it can be argued that REM sleep is necessary for the processes of remembering and maintaining a person’s mental health. Dreams, which are a companion to this part of sleep, reflect deep mental activity and in symbolic form can present to our consciousness information about existing intrapsychic conflict situations.

Why does a person fall asleep?

Where does the state of sleep objectively come from? Why is it that in the middle of the day an ordinary person does not feel the urge to sleep at all, but at night, even in a responsible position, he is ready to give everything for the sweet moments of sleep?

The human body functions in two modes. One of them is the well-studied state of wakefulness. Another, accordingly, is the state of sleep. In the state of sleep and wakefulness, almost all vital processes occur differently. This is very clearly seen in the example of changes in the electroencephalogram: electrical processes in the human brain differ significantly not only when comparing sleep and wakefulness, but even between different stages of sleep. The activity of other body systems may also differ dramatically. For example, breathing during sleep becomes 2-2.5 times less deep than during wakefulness, the heart rate slows down during sleep, the secretion of stress hormones - cortisol, adrenaline - decreases, and sleep-specific hormones are produced - melatonin, somatotropic hormone. There are many other examples that can be given.

The main factor in initiating sleep is a change in the interaction of two systems of brain neurons - activating and inhibitory. The activating system, which consists of 8 centers, provides stimulation of the cortical and subcortical parts of the brain. This is necessary in order to maintain a sufficient level of consciousness, quickly respond to changing circumstances, ensure a coordinated response of internal organs to these changes, and receive and use information. If the activating system is damaged, such as in a brain stroke, the person goes into a coma. The main “carriers” of information from activating centers to other parts of the brain are acetylcholine, norepinephrine, glutamate, histamine and a number of other substances.

There are significantly fewer centers related to the synchronization system of the brain, or “sleep centers.” Two of them are the main ones - they are located in the forebrain and hypothalamus and contain the universal inhibitory substance gamma-aminobutyric acid and the peptide galanin, which is important for sleep. A person begins to experience drowsiness when the sleep centers begin to work intensively and suppress the activity of the activating brain centers. Subsequently, a self-sustaining mechanism is activated when the brain begins to disconnect itself from external stimuli, at the same time causing cortical neurons to generate electrical activity characteristic of a sleep state. After the brain has been in slow-wave sleep for a sufficient amount of time, a complex interaction of neural nuclei in the brainstem initiates REM sleep. The end of REM sleep completes the first sleep cycle, after which the entire sequence of sleep stages repeats.

Researchers suggest that two additional factors play a major role in the processes of sleep initiation (slow-wave sleep): the accumulation of the mediator adenosine (fatigue mediator) during the day and the increase in the evening of impulses from the body’s internal clock (suprachiasmatic nuclei). In addition, the likelihood of sleep is also affected by the accumulation of the “sleep hormone” melatonin, the production of which begins to increase with a decrease in the light flux from the outside (when it begins to get dark).

In order to explain why a person falls asleep every day, for example, at 0 o’clock, and not at 11 or 15 o’clock in the afternoon, a “two processes” model has been proposed. According to it, as you stay awake, a certain substance or complex of substances - hypnotoxin - accumulates in the body (remember the experiments of French researchers on sleep-deprived dogs). More than a dozen substances claim the title of hypnotoxin, but none of them have yet demonstrated a clear hypnotic effect in human experiments. Simultaneously with the increase in the level of this hypothetical hypnotoxin in the body, in the evening the level of brain activation, depending on the activity of the internal clock, declines. In this way, the “gates of sleep” open; you just need to enter them. If a person eliminates external stimuli and takes a relaxed horizontal position in bed, then, most likely, sleep will begin - the sleep centers will begin to suppress the activating centers and falling asleep will occur. During the night, as sleep continues, the hypnotoxin will gradually be neutralized and brain activity will begin to increase in accordance with signals from the internal clock. In this case, a moment will come when the “gates of sleep” will close - awakening will be possible even from a minor internal or external stimulus and the dream will end.

How much sleep do you need?

Can a person not sleep at all? It is often mentioned that the torture of sleep deprivation was the most terrible torture inflicted on a person, forcing him to lose his “human appearance” within a few weeks and tell everything to his tormentors. In 1965, the Guinness Book of Records recorded the first (and only confirmed) record of staying without sleep for 264 hours (11 days), which belonged to the American student Randy Gardner. After 4-5 days of lack of sleep, the subject began to feel weak, irritable, suspicious, and periodically experienced hallucinations. After the end of the experiments, Randy slept for 14 hours and 40 minutes, and the doctors declared him completely healthy. Subsequently, representatives of the Guinness Agency refused to register this kind of records, since they are associated with danger to life and health. However, in 1977 in the UK, Maureen Weston, participating in the Rocking Chair Marathon, managed to stay awake for 449 hours (18.7 days).

Sleep scientists are skeptical about the reliability of these kinds of records. To prove that a person has definitely not been sleeping all this time, it is necessary to continuously record polysomnogram readings. In experiments on volunteers, it was shown that even after 2-3 nights without sleep, periods of “microsleep” lasting 10-30 seconds begin to interfere with the usual waking EEG and a pure experiment does not work, because in total several hours of sleep are still gained per day. Most likely, sleep is such a vital motivation for the body that it is simply impossible to completely eliminate its occurrence for a long time.

How much sleep does a person need to get enough sleep and feel good? Currently, it is believed that the need for sleep is genetically determined and remains virtually unchanged after a person reaches adulthood. It is not true that older people need less sleep than younger people; they simply have more reasons to sleep poorly. There are historical accounts of people who slept very little and yet worked actively and even had a significant impact on the course of history. So they say that Leonardo da Vinci slept 1.5 hours a day, Nikola Tesla - 2 hours, Napoleon Bonaparte - 4 hours, Winston Churchill and Thomas Edison - 4-6 hours each. It is not possible to verify these statements. Scientists have conducted several studies of short-sleeping people who slept for 3-5 hours. The peculiarity of their sleep was that the deepest sleep - delta sleep - took up at least half of their entire sleep time, that is, their sleep efficiency was maximum by limiting the time of less important stages of sleep.

It is believed that for most people, a “healthy norm” is sleep for 7.5-8.5 hours. To determine your personal, individual need for sleep, during the “experiments” you need to provide yourself with the most favorable conditions and exclude external factors that can distort the picture - work, stress, unfavorable natural and social background. The approximate duration of your own sleep should be determined during 2-3 weeks of vacation, “without excesses,” after chronic lack of sleep, typical of many actively working people, has been compensated.

Characteristic of modern society is the deliberate limitation of sleep in favor of increasing work time or, conversely, rest time in the evening and at night. This effect is also called the “Edison effect,” paying tribute to the famous American inventor who improved the incandescent electric lamp in order to produce it in mass quantities and, figuratively speaking, “turn night into day.” It is not yet possible to determine exactly how long a person can exist in conditions of sleep restriction without consequences for himself. Nevertheless, a number of evidence has already been obtained about the negative impact of long-term sleep restriction on health.

A person stays awake for sixteen hours and sleeps only for eight. During this process, he sees vivid dreams. But why do people need dreams and what is it? Sleep is a process that occurs in living organisms. For human physiology, it is a natural process, a vital need of the human body. It is as important as food. Sleep is a complex brain.

What is sleep?

Sleep is a state of the human body and other living beings (animals, insects, birds), in which the reaction to external stimuli decreases. NREM sleep is a state after falling asleep that lasts 1-1.5 hours. In this state, the information received during the day is absorbed and strength is restored.

Why is sleep needed and what stages does it go through?

At the first stage, the respiratory rate, pulse rate and heartbeat decrease, the temperature drops and spontaneous twitching may be observed.
In the second stage, the heart rate and temperature continue to decrease, the eyes are motionless, receptivity increases, and the person can easily wake up.
The third and fourth stages refer to deep sleep; it is difficult to wake a person; it is at this time that about 80% of dreams are formed. Also, it is at this time that cases of enuresis, attacks of sleepwalking, nightmares and involuntary conversations occur, but the person is unable to do anything about it, and after waking up he may not remember what is happening.

REM sleep

REM sleep occurs after slow sleep and lasts from 10 to 15 minutes. Pulse and heart rate are gradually restored. The person is motionless, but his eyes can make rapid movements. During REM sleep, it is easy to wake a person.

What is a dream?

During sleep, changes are observed in the brain and spinal cord. It is a combination of several different phases. When a person falls asleep, he goes into a state of slow-wave sleep. It is popularly called napping. After some time, a transition occurs to the second state. It's called "Morpheus's embrace." The third state is called deep sleep. From a state of deep sleep, a person moves into the fourth state. The fourth state is called sound sleep and is considered final. It's almost impossible to wake up in it.

In a state of slow sleep, the human body begins to produce growth hormone, the regeneration of tissues of internal organs and skin begins, and the pulse decreases.

Sleep structure

The structure of sleep consists of phases. They repeat and alternate with each other every night. A person experiences slow and fast sleep during the night. There are five. Each cycle lasts from eighty to one hundred minutes. NREM sleep consists of four states:

In the first state of sleep, a person's heart rate decreases. This state is called drowsiness. At such a moment, a person sees his dreams and hallucinations. In this state, unexpected ideas may come to a person.
The second sleep state is characterized by a rapid heartbeat. In this state, a person's consciousness turns off.
During the third stage, it will not be difficult to force a person to wake up. At this moment a person becomes very sensitive to any irritants. At this stage, a person’s hearing becomes more acute. During sleep, a person may be awakened by a slight noise. The pulse remains the same.
In the fourth state, a person is in a state of deep sleep. Sometimes the third and fourth are combined into one. This general state is called delta sleep. At this moment it is very difficult to force a person to wake up. Often at this stage you can dream. You may also have nightmares.

The four sleep states take up 70% of the entire process. Therefore, another factor in why sleep is needed and why lies in the restoration of expended resources.

Sleep functions

The functions of sleep are to restore vital resources used up while a person is awake. Also during sleep, vital resources accumulate in the human body. When a person wakes up, vital resources are activated.

Performs an information task. When a person sleeps, he stops perceiving new information. At this moment, the human brain processes the information accumulated during the day and systematizes it. Sleep performs psychological functions. At the moment of sleep, emotions become active in a person. A person’s coordination becomes passive, and immunity begins to recover. When a person sleeps, his mental and emotional state returns to normal. Sleep helps you adapt to different lighting conditions. During sleep, human organs and the entire body system are protected and restored.

Does a person need sleep? Yes, it allows you to solve important and complex problems and includes the body’s protective functions.

Sleep disturbance

Every person experiences sleep disturbances. Some people cannot sleep properly, while others, on the contrary, want to sleep during the daytime. If this does not happen often, there is nothing to be afraid of, but if it happens often, it is already a disease. If this happens rarely, the person does not have major problems.

If sleep patterns are frequently disrupted, a person cannot lead a normal life, this indicates that he is sick. Only 10% of people suffering from this come to the hospital for help. The rest are trying to cope with the disease on their own. To do this, they self-medicate. Other people do not pay attention to the disease.

Insomnia as a pathology

Sleep disorders include insomnia. With such an illness, it is difficult for a person to fall asleep; he cannot fall into a sleepy state. More often, the disease occurs due to mental illness, nicotine, alcohol, caffeine, medications and stress.

Absolute sleep disturbance can be directly related to household factors and changes in work schedule.

What are dreams for?

Sleep is beneficial for the human body:

Eliminates tension in the muscle and nervous system.
Restores concentration.
Improves attention and memory at this moment.
Reduces the risk of heart disease by 49%.
After sleep, a person becomes energetic, cheerful, and there is a desire to engage in creative activities.
Daytime sleep allows a person to get enough sleep in cases where this is not possible at night.
In half an hour of sleep, a person finds answers to the most difficult questions.
At this time, the brain works intensively, and the body is in a relaxed state.
When he wakes up, he doesn’t feel the nervousness that he had. A person stops developing stress.
When he wakes up, he feels happy, since by this moment his level of the hormone of happiness in his blood increases.
While in a state of drowsiness, a person seems to enter a state of meditation. At this moment, his connection with the outside world begins to be disrupted.
A person has a close connection with the subconscious.
At this moment, a person has brilliant ideas and unexpected discoveries.

Sleeping during the day - benefit or harm?

Rest during the day is typical for a child. Whether sleep is necessary for adults is a different question; it all depends on individual characteristics. After morning sleep, a person becomes cheerful, energetic and has clarity of mind. A little morning sleep gives a boost of positivity throughout the day. Helps when a person does monotonous work and during weather changes. It improves imagination, concentration and attention, which is why many people like to sleep during the day.

But is napping necessary and how important is it? Scientists have been able to prove that it helps in the fight against stress and diseases. Supports regenerative processes in the human body. During sleep, a person becomes younger. Such a dream relieves psychological and muscle tension in a person. This sleep allows you to reboot the human body. As a result, the human body is debugged. During morning sleep, a person finds solutions to issues that concern him. Having woken up, a person realizes what the answer to the question that worries him is.

It does not always allow the body to recover. It happens that after it a person feels overwhelmed and tired. What is the reason for this factor? A person should not sleep too long during the day, otherwise disturbances in the perception of time will occur.

How much sleep do you need?

People who get the same number of hours of sleep at night have twice the life expectancy of a person whose sleep duration is reduced to a minimum. In order for sleep to bring maximum benefits, scientists have found that adherence to the regime is an integral part of life. Otherwise, the biological clock gets lost and health problems begin.

The duration of sleep will be more productive if you sleep continuously for 7-8 hours. It has been proven that 6 hours of continuous sleep has a beneficial effect on a person’s condition than 7-8 hours of interrupted sleep. A person who awakens from sleep must get used to the regime. In order not to fall asleep again after waking up, you should not lie in bed for a long time; the body quickly adapts to the changes.

Doctors recommend: spending a lot of time in the fresh air, not eating too much 2 hours before bedtime, taking relaxing baths, trying not to sleep during the day, purchasing a comfortable mattress and pillow, and maintaining a continuous sleep schedule for 7-8 hours. If a person has had enough sleep, then when he loses control over the task, the brain restores attention, but the brain of a person who has not had enough sleep is not fully attentive and focused, and does not perceive the world around him correctly.

Long-term sleep is considered to be 10-15 hours a day. During such sleep, a person quickly becomes overtired. He develops diseases such as obesity, problems with internal organs and blood flow begin, and people are overcome by laziness, apathy, and confuse the time of day (day and night).

It is vital to get enough sleep to restore your emotional background and physical strength, as well as to allow your body to renew its strength during and after illness. Each person needs to choose an individual schedule in order to get enough sleep and be alert, so there is no clear answer to the question of how much sleep a person needs to sleep.

With silent steps he approaches me - the most pleasant of thieves, and steals my thoughts, and I freeze in place... Friedrich Nietzsche

Every night we all fall asleep and sleep until the morning. About 8 hours a day and about 25 years in my entire life. Sleep is vital, and a person must sleep every day and for a sufficient amount of time.

In some cases, we find ourselves deprived of the required portion of sleep - for example, due to night shifts at work. Even one night without proper rest worsens your well-being, mood and performance. Not sleeping for two, three or more nights in a row is extremely difficult and even more harmful.

The documented world record for no sleep is 11 days, set half a century ago by a young American, Randy Gardner. By the end of the experiment, the brave natural scientist was in a state of psychosis, suffered from hallucinations and did not remember his name. If you do not allow a person to sleep at all, after about 2 weeks he may die from severe brain disorders. Why is sleep needed, what is the reason for its exceptional importance and what is it even?

What is a dream

It’s hard to imagine, but today there is no absolute definition of sleep. To give a rough description of the term, sleep is a normal physiological state in which a person has a reduced reaction to the outside world and the goal of which is rest and recovery.

Previously, people had a very primitive idea of the physiology of sleep. They believed that during sleep the soul leaves the body and travels around the world (the global information field? the astral world?). What she sees during her “journey” is remembered by a person as dreams. Now we can say with confidence that we do not go to the astral plane in our dreams. However, the origin of the dream is still full of mysteries. Humanity is tens of thousands of years old, and during this time we have not figured out what sleep is! Somnology - the science of sleep - arose only about 50 years ago, and during this time, despite its fairly rapid development, it has not yet managed to answer questions about the physiology of sleep and its functions.

In fact, only three things are completely obvious.

The sleeper is in a state of relaxation and almost complete immobility.
During sleep, a person has a limited perception of reality. It is impossible to say that perception is “turned off” completely: it has been proven that sleeping people can react to odors, in addition, everyone can be woken up by the ringing of an alarm clock.
During sleep, amazing cyclical processes occur in the brain that distinguish sleep from wakefulness and other similar states: coma, fainting, hypnotic trance.

The subtleties are still unknown to scientists. However, they were able to study the structure of sleep and describe some of the processes occurring in the body while a person sleeps.

Sleep structure

Most people sleep once a day, at night. From the outside, sleep looks quite monotonous, predictable, even boring: a person goes to bed in the evening, closes his eyes and remains in bed until the morning. However, in reality, sleep is a very dynamic phenomenon. This has been proven by research into the processes that occur in the brain of those who sleep.

It's no secret that the human body produces weak electricity. When the heart, muscles and other organs work, an electromagnetic field is generated. The brain is a particularly active “electric generator”. Its bioelectrical activity changes significantly throughout the night. The study of this activity using encephalography allowed specialists to learn about the structure of sleep and identify its cycles, phases and stages.

The usual duration of night sleep is 7-8 hours. This period consists of several (4-5) identical “pieces”, which are called cycles. Each cycle includes a certain sequence of phases and stages.

After a person falls asleep, he enters the slow-wave sleep phase. Such a dream is called “slow” because during its duration a person’s eyes, under closed eyelids, make slow floating movements.

Islow wave sleep stage(sometimes also called napping) occurs immediately after falling asleep. This is the most superficial sleep that is easily disturbed; If you wake a person during stage I sleep, he often denies that he managed to fall asleep. In terms of time, stage I lasts no more than 5% of the duration of the entire sleep.

II slow wave sleep stage during it, specific phenomena appear on the sleeper’s encephalogram - “sleep spindles” and “K-complexes”. One recent study has linked them to memory performance, although their function is not yet fully understood. In stage II, sleep gradually deepens, although it is still superficial sleep. Its duration reaches up to 60% of the total sleep time.

Previously, two more deep stages were distinguished in slow-wave sleep – III and IV. However, not so long ago the American Academy of Sleep Medicine combined them into one - delta sleep, or slow-wave deep sleep. It occurs after phase II. At this time, a person’s body temperature and heart rate decrease as much as possible, muscle tone decreases, and many important hormones are released. This is the deepest sleep; waking a person during this period is the most difficult. During delta sleep, the sleeper experiences his first dreams, and this stage is also the most vulnerable to various disorders. It is with delta sleep disorders that a person experiences sleepwalking, night terrors, enuresis, and talking in his sleep.

After delta sleep comes REM sleep (R.E.M.-sleep, rapid eye movement stage of sleep). The moment of transition can be determined even if the person is not “connected” to the encephalograph. It is enough just to look at the sleeping person from the side. Rapid eye movements occur during REM sleep. The state of the sleeping person’s brain at this time resembles that during wakefulness, breathing and heart rate increase. In REM sleep, a person sees the greatest number of dreams, and if you wake him up during this phase, he remembers them very well. However, in general, awakening during REM sleep is almost as difficult as during deep stages of slow-wave sleep.

An interesting feature of REM sleep is that the sleeper's body muscle tone decreases - in fact, he becomes paralyzed. It is assumed that the purpose of this phenomenon is to prevent a person from repeating the movements that he makes in his dreams.

After the end of the REM sleep stage, the entire “sleepy” cycle ends. The brain is briefly stimulated and then moves on to the next cycle, which includes an identical sequence of phases.

One cycle lasts about 90 minutes. That is why waking up in the morning occurs most easily when the time from the moment of falling asleep is a multiple of 1.5 hours. A person wakes up at the border of two sleep cycles, when his sleep is most superficial and it is easiest to transition to wakefulness.

Sleep functions

When asked why sleep is needed, everyone will answer: so that the body can rest! But is he really resting?

Yes, during sleep, muscles relax, the speed of metabolic processes decreases, and all organs work at half capacity. But the changes occurring in the sleeping brain do not allow us to say that the nervous system is also resting.

There is an expression: “A change of activity is the best rest.” For the brain, sleep is just a change of activity, but not relaxation. All night the nerve centers are in full swing - the brain implements the functions of sleep.

So, why should a person sleep?

Organs and muscles get a “break”
The body replenishes energy resources
During sleep, under the guidance of the brain, “cleaning” occurs in the body; the processes of binding and neutralizing toxins are actively underway. The brain also cleanses itself. In 2012, foreign scientists discovered the glymphatic system - a system of microtubules in the brain that opens during sleep and is responsible for removing toxins from the central nervous system.
Memorization occurs, long-term memory is formed, and new skills are consolidated.
A “scan” of the body is carried out - analysis of the state of organs, as well as elimination of identified problems.
The state of immunity improves, since it is during sleep that the most active formation of immunocompetent cells occurs.

Sleep disorders

A person's sleep can be affected by various internal and external reasons. In total, according to the modern classification, there are 89 sleep diseases. They are studied by the science of somnology.

Among sleep diseases, the most common types are various types of insomnia (10-15% of the population - chronic insomnia, up to 40% - episodic), snoring (one third of adults), obstructive sleep apnea syndrome (4-7%), restless legs syndrome. Less often, somnologists encounter other disorders.

There are also diseases that most doctors have never encountered - they are so rare. For example, there is a genetic disorder called fatal familial insomnia. Throughout the history of medicine, cases of this disease have been reported in representatives of only 40 families in the world.

In our country, somnology is just beginning to develop. In total, there are about 50 somnology centers, offices and sleep laboratories in Russia - for comparison, there are about 5,000 of them in the USA.

It is better to contact a sleep specialist directly for various sleep disorders. They know exactly how to diagnose certain diseases and what to do so that each patient regains the ability to sleep well and soundly.

Absolutely everyone knows that sleep is essential for humans. If only because everyone has experienced the consequences of lack of sleep, especially if it is not possible to get a good rest for several days. A person becomes lethargic, inhibited and literally switches off while walking. A fairly large percentage of serious accidents on the roads occur due to the fact that the driver of one of the cars simply fell asleep at the wheel. But why does a person need sleep, what is its nature and what happens to the body during this period?

A little history

Dream - what is it? It was the ancient Greek philosophers who first drew attention to this very unusual condition. They believed that after falling asleep, the human soul is freed from bodily shackles and can undertake long journeys. She is able to return back to the body thanks to the thinnest silver thread that is connected to it. If this thread is broken, death occurs.

Approximately the same ideas about what sleep was were during the Middle Ages. They were also mixed with fear of witchcraft, since it was believed that a witch could penetrate someone else's dream, break the thread connecting the soul with the body and steal the soul or use the body of the former owner at her own discretion. In the 18th and 19th centuries, it was believed that with the help of sleep one could penetrate into higher spheres and even communicate with the souls of the dead, but people did not have the slightest idea about the very nature of sleep.

It was possible to shed some light on why we need to sleep only at the end of the 19th century, when this phenomenon began to be systematically and purposefully studied by scientists as a biological function of the body. The first experiments were carried out on animals and were quite cruel. Russian physiologist Victoria Manaseina deprived adult dogs and their cubs of sleep.

The puppies died already on the 4-5th day, the adults managed to hold out for up to two weeks, but after 6-7 days they became very weak, refused to eat, and became practically motionless, not reacting in any way to external stimuli.

It turned out that sleep is much more important for living organisms than previously thought.

At the beginning of the last century, they switched from experiments with animals to human studies. Already on days 2-3, people deprived of sleep become very irritable, their reactions slow down, and their appetite disappears. By the fifth day, severe weakness appears, the level of immune defense sharply decreases, all chronic diseases (if any) worsen, severe headaches and periodic blackouts appear.

Cycles and phases

The advent of electrical devices in the 40s and 50s simplified the task of sleep research and made it possible to analyze the brain activity of a sleeping person. And then the first surprises awaited the scientists. It turned out that the brain not only continues to work in sleep, but sometimes becomes even more active than in some waking states. Moreover, the changes in its activity showed a clear periodicity.

Scientists divided the entire sleep period into phases, during which certain patterns were observed in the functioning of the brain. The two main periods, named after the visible movement of the eyeballs under the closed eyelids of a sleeping person, were slow-wave sleep and rapid eye movement sleep. But upon further research, it turned out that slow-wave sleep has four main phases:

After 20-30 minutes, brain activity increases sharply and the person enters the REM sleep phase. The eyeballs, which had been rotating slowly until then, begin to move very quickly, chaotically changing direction. It seems that the sleeper is trying to keep track of something. Indeed, at this moment a person usually sees a vivid dream, which he can easily retell if he is woken up before returning to the slow phase.

In just one night, a person goes through several such cycles, the total length of which is about 90 minutes. The only exception is the stage of drowsiness, which the sleeper goes through only when falling asleep.

In the morning, the fourth stage shortens, and the fast period increases. This is the secret of the fact that a person remembers only the last dream of the night, and then not for long - until it is supplanted by new impressions.

Biological significance

Having studied what happens to the human body and brain after falling asleep, scientists were able to more or less accurately determine the biological meaning of sleep:

Thus, it turned out that while the physical body relaxes, the brain has time to both rest and work hard. And this is the main paradox of sleep, which scientists still cannot solve.

Interestingly, if the brain is forcibly turned off with the help of drugs or strong sleeping pills, then in the morning a person does not feel rested. Moreover, he is deprived of the REM sleep phase and falls into a “heavy” sleep without dreams, during which the attunement of all organs and systems does not occur. The person “turns off” but does not recover correctly.

When is the best time to sleep?

But if sleep is so important, and the processes that take place during it are standard, then is it possible to replace night rest with the same amount of daytime rest? It would seem that the answer is obvious - what difference does it make when you sleep your eight hours. But after the first experiments, scientists were in for a new surprise. It turned out that daytime and nighttime sleep are completely unequal. And the reason for this is the circadian rhythms inherent in the human genetic apparatus.

Circadian rhythms are a kind of built-in biological clock that helps the body determine when it’s time to go on vacation. They are inextricably linked with light exposure - in the morning the body is more active and ready for work, and in the evening all body functions slow down and it begins to prepare for sleep.

A special hormone, melatonin, which is produced from approximately 10 pm to 2 am, helps with this. If there is not enough melatonin, then a person experiences difficulty falling asleep, since the activity of biological processes does not decrease enough. This is one of the reasons why insomnia often plagues older people.

Melatonin production is promoted by reduced levels of natural light. For our ancestors, it began to be actively produced by the body after sunset, so they went to bed early - at 20-21 o'clock, and got up at sunrise. We use artificial lighting, so it is more difficult for the body to navigate. That is why it is important not to use bright light for an hour or two before bedtime, but to slightly dim the lighting.

But even if a person is placed in conditions where there are no light fluctuations, he will get up and go to bed at approximately the same time. Its daily activity will still remain cyclical, but this cycle will lengthen slightly and, with a long stay without changing lighting, can stretch up to 30-36 hours.

During the day, little to no melatonin is produced, even if the curtains are tightly closed. Therefore, even if a person has worked all night, he will be able to sleep no more than 3-4 hours during the day, and this is absolutely not enough to compensate for a night’s rest.

People who constantly work night shifts often suffer from chronic fatigue syndrome and various psychosomatic diseases caused by a permanent lack of sleep.

However, a short daytime rest, no more than 1-1.5 hours, is very useful, especially in the afternoon. Intuitively, this discovery was made by residents of most countries with temperate and hot climates, in many of which the national tradition is the siesta - an afternoon rest, during which all shops and businesses are closed, and people sleep or are simply in a relaxed state.

Such sleep improves digestion (and the load on the gastrointestinal tract after eating lunch, which usually consists of 2-3 dishes, is maximum!), lowers blood pressure, relieves the cardiovascular system and restores muscle activity.

Therefore, if there is an opportunity for a short rest between 13:00 and 15:00, try to use it. This heals and rejuvenates the body, strengthens the immune system and even increases life expectancy by several years.

Consequences of sleep disturbance

For various reasons, some people experience various sleep disorders:

All these disorders must be treated. And often it is not possible to do without the help of a specialist, since they have physiological and psychological causes that need to be clarified, and not just temporarily remove unpleasant symptoms with the help of medications.

Long-term sleep disturbances lead to the development of psychosomatic diseases and mental disorders. The hormonal balance is disrupted, the cardiovascular and nervous systems are overloaded. People with sleep disorders are several times more likely to have heart attacks and strokes, they age faster, and they are more likely to be involved in road accidents.

A person's daily need for sleep is 8 hours - a third of his life. This physiological process consists of reducing a person’s reaction to the environment and restoring the body.

People have long believed that the soul of a person, when he falls asleep, leaves the body, and all the positive or negative aspects of its wanderings were postponed and reflected in dreams, being in the so-called astral world. The science of sleep - somnology, which emerged in the last century, refutes this fact, although questions about the concept of sleep, physiology, and its functions are still open.

What happens to the body in the absence of proper sleep?

Through many experiments, during which people from different countries of the world tested their bodies with insomnia, it turned out that without sleep, a person’s condition worsens in a certain pattern. On the 3-4th day of insomnia, fatigue and irritability appear. On the fifth day, vision decreases, hearing deteriorates, coordination of movement is impaired (and with a balanced and timely diet), and hallucinations are observed. Subsequently, motor skills and speech are impaired.

The record for insomnia of 8 days was recorded in 1965 by Randy Gardner.

Subsequently, experiments began to be carried out on animals. And the results showed that insomnia ultimately leads to death due to weakened immunity, nervous system disorders and improper functioning of internal organs.

There are about 89 diseases that are caused by poor or lack of sleep. Common ones include insomnia, snoring, sleep apnea and restless legs syndrome. Benefits of sleep. Why is sleep so necessary?

As a result of work, toxins are formed in brain cells, which lead to a tired state. During proper sleep, they are eliminated by blood circulation. Thus, in 2012, researchers at the University of Rochester (led by Maiken Nedergaard from Denmark) discovered the glymphatic system, which during sleep begins to remove toxins from the human nervous system.

Also, during sleep, there is no need to analyze information received from the outside world, since vision, hearing and the body as a whole operate in economy mode. At this moment, information is processed that occurs inside the body, and not obtained through visual perception of the surrounding world.

It is important for a person to fall asleep in a horizontal position, since in this case the brain and heart are at the same level, which means blood circulation becomes better.

Only 3% of people who sleep 6 hours a day feel normal. They owe this to their genetic characteristics.
The ideal time to fall asleep is considered to be between 10 and 15 minutes. This means that you are quite tired, but during the day you were cheerful and active.
New parents often suffer greatly from lack of sleep. A new member of the family deprives its parents of 400-750 hours of annual sleep.
Out of 6 road accidents, 1 occurs due to driver fatigue.
Our internal clock, with the help of which we can wake up a few minutes before the alarm, works thanks to the hormone adrenocorticotropin. If its level increases sharply, then the person feels unconscious stress associated with the rise.
While snoring, a person cannot dream. Moreover, snoring can indicate that a person is in the slow phase of sleep.
The most important enemy of proper sleep is the Internet, which is available around the clock to almost every inhabitant of the Earth.
Regular lack of sleep can cause weight gain. The fact is that a tired body tries to make up for the lack of resources in any way. This is why when you don’t get enough sleep, you feel hungry more often.
Scientists say that all people, without exception, have dreams. Those individuals who claim the opposite most likely simply do not remember their nightly “adventures.”
Many famous people slept strangely, to put it mildly. Leonardo da Vinci practiced phased sleep: every 4 hours he rested for 15 minutes. Albert Einstein slept no more than 4 hours a day, and Nikola Tesla - 2 hours a day.

It is important for a person to fall asleep in a horizontal position, since in this case the brain and heart are at the same level, which means blood circulation improves.

Sleep is a physiological state of the body that is necessary for every living organism. The body needs restoration, recharging, in order to continue to explore the world around us with renewed vigor.. There is no need to waste time on sleep and deprive the body of such important moments. It must be remembered that human health, his life depends entirely on sleep.