Sleep physiology

A person spends on average a third of his life sleeping. So, out of thirty lived years, ten pass in a passive, inactive state with a switched off consciousness. This may seem offensive: after all, we value our time so much. You shouldn't be upset. Sleep is necessary: it is healing. The need for it is stronger than for food. In an experiment on dogs, Academician I. R. Tarkhanov found that dogs recovered completely after 25 days of fasting, but died after five days of insomnia.

What happens if you do not sleep for 3 days or, say, a week?

It is known that overwork most of all affects the central nervous system, in particular, the nerve cells of the cerebral cortex. After all, it is on them that the greatest load falls, since the cerebral cortex is the leading organ and all the processes occurring in our body are carried out under its “supreme guidance”.

The feeling of fatigue increases especially in the evening - the head becomes heavy, thoughts "get confused", I want to sleep.

Look at the sleeping person. During sleep, he is motionless, very rarely a person twitches in a dream, only occasionally changes the position of the arm, leg, turns to the other side. All this is done automatically, without any participation of consciousness, which is inhibited. Almost all the muscles of the body are in a state of significant relaxation. The activity of cardiovascular activity also decreases somewhat. When listening to the heart, it is easy to determine that the rhythm of its work is different than during wakefulness - weaker. The blood pressure also drops by 20-25 millimeters of mercury. Blood flows more intensively to the vessels of the skin, while the vessels expand. That's why sleepers usually have flushed faces. Increased heat transfer leads to a decrease in body temperature.

Breathing during sleep also changes: it becomes less frequent, smoother, deeper. Sometimes people snore in their sleep. So why do people snore in their sleep? This is due to the "flaccidity" of a special muscle. During deep sleep, the lower jaw drops slightly, the muscles relax. At the same time, the sleeping person's mouth opens slightly, and air enters the lungs not only through the nose, but also through the half-open mouth. On the way to the windpipe, the air collides with the so-called soft palatine curtain, which has descended, as it were, in the form of a canopy between the oral and nasopharyngeal cavities.

The muscles of the palatine curtain during sleep, like all the other muscles of the sleeping person, are also relaxed, sluggish. The passing air shakes it, it seems to begin to tremble - "clap". Hence the snoring.

During sleep, oxidative processes and metabolism slow down. The kidneys also work less intensively, excreting 2-4 times less urine than during the day. What causes dry mouth? - The amount of secretions from the glands of the skin of the face, mouth, eyes and nose is reduced. This explains that an awakened person often feels dry mouth, burning eyes. And, conversely, the activity of the sweat glands increases: people often wake up in perspiration. As for the work of the organs of the gastrointestinal tract, their functional ability in sleep decreases slightly.

The nervous system also rests. Irritations of the external environment, if they are not very intense, in most cases do not reach the sleeping person - he does not react to them. Thus, the body during sleep spends a minimum of its physiological resources to maintain contact with the external environment.

According to the teachings of I.P. Pavlov, sleep is diffuse inhibition, spreading to all higher parts of the brain, protecting and restoring nerve cells from harmful exhaustion and destruction. However, the phenomena of inhibition do not completely cover the entire mass of the brain. Some of its departments continue to function actively during sleep. So, for example, everyone knows that a mother who falls asleep at the cradle of a child does not hear the noise coming from the street, even if it is strong. But then the child moves, and the mother immediately wakes up, another example. the telegraph operator on duty accidentally dozed off at the apparatus. No noise wakes him up. But as soon as the telegraph apparatus begins to transmit material, the telegraph operator wakes up.

These facts, as well as many others, indicate that there are some more active zones in the sleeping brain, the intensity of which decreases only during very deep sleep. These zones are called "guard" points. They are vital and active in many people. Let's take another example. A person has to catch the train early in the morning. He worries about oversleeping, and, to his surprise, wakes up at the right time. It seems that someone "followed" the passage of time. The role of the alarm clock was performed by the so-called "watchdog" item.

True, some people even during the day without a watch have a sense of counting time, but in a dream it manifests itself stronger and more clearly, because it is not obscured by other impressions, of which a waking person has many. There are cases when the creative process can continue during very deep sleep.

In-depth studies carried out by students of I. P. Pavlov provided a number of new data on the processes that occur during sleep in the cerebral cortex. Of great importance in this regard are the works of I. P. Razenkov, full member of the Academy of Medical Sciences, who studied the internal mechanisms of sleep inhibition in laboratory conditions as early as 1923-1924. Starting this research. IP Razenkov knew that the process of excitation stimulates the activity of the brain, and the process of inhibition turns it off. However, the physiological mechanisms of the transition of the nerve cell from the period of wakefulness to sleep have not yet been elucidated. Here are the conclusions he came to: the inhibitory state does not immediately cover the nerve cells; it turned out that as it deepens, nerve cells pass through a series of intermediate states, called "phase". If, under waking conditions, a nerve cell responds to strong stimuli with strong excitation, and to weak ones with a weak reaction, then during the transition to an inhibitory state, violations of these patterns occur, that is, the normal reaction of the nerve cell perverts! Strong stimuli cause a weak reaction in nerve cells during sleep, and vice versa, weak stimuli often lead to maximum excitation.

This is how a paradoxical effect or a paradoxical phase arises. Besides her. Equalizing, narcotic and ultra-paradoxical phases have also been identified. During the equalizing phase, the brain reacts equally to both strong and weak stimuli. And during the ultraparadoxical phase, not quantitative, but qualitative manifestations of the reflex activity of the brain come to the fore, that is, excitatory stimuli cause deep inhibition, and inhibitory influences, on the contrary, lead to excitation.

Why dream?

During sleep, in accordance with the depth of inhibition occurring in the brain of the sleeper, one phase state passes into another. Phase states are directly related to the emergence of dreams.

The fact is that the brain stores most of the impressions for a long time, but in the waking state, a person chooses from all this mass only those that he needs at the moment. Something else happens in a dream. The inhibited higher parts of the brain do not manage the "treasury" of memories (it can be called the "treasury of trace reactions"). With deep this, trace reactions are inhibited.

Partial disinhibition of sections of other parts of the cerebral cortex of a sleeping person depends on various reasons and is of a disorderly nature. Therefore, often trace memories are combined with each other in the most bizarre way, without any logical expediency.

The outstanding physiologist I.M. Sechenov called dreams "an unprecedented combination of experienced impressions." After all, despite all the absurdity and pretentiousness of dreams, they are always based on some kind of memory.

It has been established that different types of experiences correspond to different depths of sleep. So, during a nap, we passively surrender to the flow of our thoughts. In superficial sleep, dreams form into coherent pictures. During deeper sleep, they appear in the form of fragmentary, often strange, little interconnected images, often even difficult to explain.

Irritations play a leading role in the formation of a dream. This has been known to people for a long time. The outstanding Greek philosopher Aristotle, who lived two thousand years ago, wrote that if a source of heat is brought to the sleeping person’s hand, then the person will dream of fire. And here is a similar dream. A man dreams of a fire in a theater. The flame lit up everything around. He sees how panic seizes the audience. He wakes up in horror and is relieved that it was only a dream. And he was called by a hanging electric light bulb that shines directly into his eyes.

Dreams sometimes reflect the most emotionally colored experiences of the sleeper, that which excites and occupies him most of all. That is why a person in a dream often sees himself in his working environment: if, moreover, he had some great experiences of trouble or, conversely, joy at work, then variations of these experiences can also be reflected in dreams.

This, apparently, should also explain that during the war years, people who were in the rear often saw in a dream the death of their loved ones who fought at the front. Anxiety for them, fear for their lives, fear that they would die, gave rise to the formation of appropriate pictures in dreams.

Why do you have nightmares?

Various ailments also contribute to heavy sleep. Sometimes a person has nightmares if he had a hearty dinner before going to bed and a full stomach reflexively affects cardiovascular activity. It also happens that dreams serve as the first harbingers of an incipient disease. I have seen a similar case. A man dreamed that he fell ill with a sore throat: it “scarred” in his throat, he felt unwell. However, he woke up healthy and thought: "It's good that it was only a dream." And in the afternoon he really fell ill with a sore throat. Consequently, the person did not notice the first little perceptible symptoms of the disease when he was awake, but they already existed and served as the basis for the dream. Clinical observations have shown that dreams filled with anxiety, fears and ending with sudden awakenings can be the cause of heart disease.