Sleep and wakefulness. The mechanisms of sleep and wakefulness of the body. Sleep as a special activity of the brain. sleep theories. Modern ideas about the nature of sleep. The meaning of sleep. Violation of the sleep-wake cycle
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The current perceiving, regulating, coordinating and controlling activity of the human brain is constantly carried out against the background of various states.
- At one end of the spectrum of these states is active wakefulness,
- On another - deep dream.
brain rhythms significantly different in different states. A person makes the main contacts with the outside world in a state of wakefulness, which is characterized by a level of brain activity sufficient for active interaction with external environment. The electrical activity of the brain during wakefulness is characterized by desynchronization, it presents various brain rhythms, mainly in the range of 8-40 Hz.
waking states
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In keeping wakefulness the inner region of the pons, trunk and midbrain is involved - the reticular formation. This has been proven in animal experiments. Fibers from these areas of the brain go to the nonspecific nuclei of the thalamus and further to the cortex. Electrical stimulation of the reticular formation causes desynchronized electrical activity in the cerebral cortex. This is reflected in the increase in the encephalogram of its high-frequency components. Desynchronization is also observed during electrical stimulation of the reticular formation during sleep of the animal.
In the structures of the pons, two groups of cells with different chemical mediators are concentrated. In the blue spot, these are norepinephrine-containing neurons, in the dorsal raphe nucleus, gray-tonin-containing neurons. Both those and other groups of cells are maximally active during wakefulness - they are systematically discharged with different rhythms. During deep sleep, these neurons are inactive - their impulse activity is very rare or completely absent. The excitation of neurons in the blue spot is always associated with the impact on the body of sensory stimuli of any modality (visual, auditory, tactile), especially new, unfamiliar stimuli. These same neurons are active during periods of increased response to the environment. That is, during periods of behavioral manifestations of attention (alarming, turning towards the object of attention, sniffing, etc.). A lack of serotonin in the blood leads to prolonged wakefulness, an increase in serotonin leads to falling asleep, and an increase in the content of norepinephrine leads to awakening. When the locus coeruleus, whose neurons produce norepinephrine, is damaged, animals sleep much longer than normal.
Most of the day a person is in a state of wakefulness, however degree of attention to the surrounding events cyclicallychanges. The cycle of attention fluctuations is 90-100 minutes.
Sleep state
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Dream- a specific state of the brain and the body as a whole, characterized by significant immobility, almost complete absence of reactions to external stimuli, phases of electrical activity of the brain and specific somatovegetative reactions.
The onset of sleep is accompanied by a decrease in response to external sensory stimuli, although the electrical manifestations of their action - evoked potentials - are recorded in all stages of sleep. Changes in the body's reactivity during sleep are associated with many factors: a decrease in the sensitivity of the peripheral parts of the sensory systems; blockade of afferentation at the thalamic level, a decrease in the excitability of the central parts of the brain due to a decrease in the influence of the cortex on the reticular formation, because activity of centrifugal pathways decreases, partial blockade of effectors, etc.
Sleep phases
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Sleep phases clearly appear on the electroencephalogram and repeat approximately with an hour and a half cycle (Fig. 17.5).
Fig.17.5. Human EEG during wakefulness and sleep.
A - wakefulness, eyes are open, the gaze moves;
B - different phases of sleep:
1 - alpha waves predominate (8-12 Hz),
2 - theta waves (3-7 Hz),
3 - higher frequencies appear (12-15 Hz),
4 - delta waves (0.5-2 Hz),
5 - paradoxical phase of sleep with rapid eye movements (REM sleep) and desynchronized electrical activity of the brain.
- In a calm state in a person with closed eyes, an alpha rhythm appears, in which the frequency of the waves of electrical activity of the brain is concentrated in the region of 8-12 Hz.
- After falling asleep the amplitude of the electrical activity of the brain decreases, and the main rhythm (8-12 Hz) slows down to 3-7 Hz (theta waves).
- When deepening sleep Against the background of slow low-voltage activity, higher-voltage electrical oscillations with a frequency of 12-15 Hz appear. These are the so-called sleep spindles. They occur periodically and last no more than 1 second.
- With further deepening of sleep high-amplitude low-frequency oscillations of 0.5–2 Hz (delta waves) begin to predominate. The deepest phase of sleep is accompanied by a change in delta waves to fast low-amplitude oscillations, similar to those that characterize the state of wakefulness.
- In the last deep phase of sleep there are rapid contractions of the eye muscles.
During sleep, many autonomic and motor parameters change. characteristic of restful wakefulness. Metabolic energy decreases, pulmonary ventilation, pulse rate, body temperature, electromyogram amplitude, muscle tone, and spinal reflexes decrease. Increases blood flow in the brain. All changes are cyclic, the most significant vegetative shifts occur during paradoxical sleep. The invariable companion of this stage of sleep is short-term coordinated fine motor reactions - mimic, movements of the fingers and toes, movement of the eyeballs.
Vegetative indicators also change, acquiring the characteristics of the state of wakefulness in the paradoxical phase of sleep: blood pressure rises, heart rate quickens, skin resistance increases, etc. This is a phase of deeper sleep, in which all the muscles of the body, except for the eyes, are relaxed. If a person is awakened in the middle of this phase, he will say that he had a dream. Therefore, deep sleep with rapid eye movements is considered a period of dreams, however, a direct relationship between dreams and eye movements has not been established.
In total, a person realizes 4-6 complete sleep cycles during the night..
The first cycle contains only 10 minutes of deep sleep with rapid eyeball movements and complete muscle relaxation. Gradually, from cycle to cycle, the duration of deep sleep phases increases and its total duration during the night is 1.5-2 hours. Often this phase of sleep is called paradoxical Since the brain is in an active state and the body is practically paralyzed, the perception of external stimuli is turned off.
To regulate sleep cycles, as well as maintaining wakefulness, the inner region of the pons and brain stem is considered the most important. In animal experiments, it was found that the activity of neurons in the pontine reticular formation changes before the change of sleep phases. For example, before the onset of the deep sleep phase, the frequency of firing of these neurons increased 100 times compared to the state of calm wakefulness.
The pontine neurons, which are active during deep sleep, and the locus coeruleus and suture neurons, which are inactive during this phase of sleep, are interconnected. This means that the two most important mediator systems of the brain work together to regulate the state of the brain. Other systems of the brain are also involved in its transition from one state to another. These are dopaminergic (releasing dopamine) and cholinergic (releasing acetylcholine) neurons of the diencephalon and pons. All the systems listed above are organized as divergent networks with one input and multiple outputs. From clusters of such neurons (nuclei), their axons diverge and go to many areas of the brain, regulating their activity.
Clinical observations of patients with local lesions of deep brain structures and sleep disorders led to the conclusion that in humans, the structures surrounding the Sylvian aqueduct and located in the posterior wall of the third ventricle of the brain play a special role. Irritation of these zones by a pathological process causes a person to sleep for a long time due to the spread of inhibition to the thalamus and the cerebral cortex. Irritation of the corresponding areas of the brain of animals with electric current impulses confirmed the presence of " sleep center".
Wakefulness and sleep, being two polar functional states of a person, also reflect various states of his consciousness.
- Wakefulness implies the possibility of a person's awareness of mental and (or) physical activity.
- The processes that occur in a dream are not conscious.
A third of life is spent by a person in a dream: he sleeps for 20 years of his life out of 60, respectively, 25 out of 75 years. Man has risen to an immeasurable height above the world of animals, but sleep every day returns him to the state that takes place in animals and children. This condition has long attracted the attention of philosophers, poets, and doctors.
On the one hand, sleep is seen as happiness. “Happy is the one who sleeps, who in the rainy autumn dreams of the caresses of spring.” There is an expression "Embrace of sleep." “Happy is the one who invariably visits a dream, to whom he appears at a certain time, for a certain period of time and leaves as quietly and imperceptibly as he came,” so poetically and beautifully it is written about a dream. The philosopher Schopenhauer said: “Sleep is to man what a clock is to a factory.” “Sleep is the source of all strength, a balm for a sick soul,” Shakespeare wrote.
On the other hand, sleep was sometimes defined as a state close to death: “Dream-torturers fly over sinful people”, “Sleepy, that you are dead”, “You fall asleep that you die”, “Sleeps like a dead (deadly sleep)”.
People call sleep sweet, light, heavy, strong, nervous, tender, serene, disturbing, transparent, bewitching, deep, dead, black. Each of these definitions reflects a subjective attitude towards sleep.
In the past, sleep was divided into imperative and strong-willed. The first comes periodically in accordance with the "imperious need of the body." The imperative need is especially manifested during prolonged wakefulness, fatigue. Famous Russian linguist, creator explanatory dictionary V. I. Dal, a doctor by education, recalled how, being extremely tired, he fell asleep on the battlefield among the wounded and killed soldiers. Volitional sleep arises at will and is a luxury, a pleasure, a habit, not being necessary, it is pleasant. Such, for example, is the morning repeated sleep after waking up, when the question is being decided whether to sleep further or not, there is no longer an imperative need here, since the need is satisfied, as a rule, even before the morning awakening.
What is the normal duration of sleep? Is it good to sleep a lot? What factors determine sleep duration?
Normal sleep duration
First of all, the age factor plays a role. Based on the observations, it was believed that:
- a newborn up to 4-6 weeks is awake 2 hours a day
- in 1-2 years - 6-8 hours
- at 2-3 years - 7-9 hours
- at 3-4 years - 8-10 hours
- at 4-6 years old - 9-11 hours
- at 6-9 years old - 12-14 hours
- at 9-13 years old - 14-16 hours
In adolescence, they usually sleep 8-10 hours, after 20 years - 6-8, in middle age - 5-7. Night sleep of the elderly is somewhat shortened. We are not talking about the daily duration of sleep, often increased in old age.
The given data are specified in recent times especially with regard to sleep in children. These hours turned out to be sharply overestimated, since two states were analyzed: rest and activity according to behavioral manifestations. Electroencephalographic data have shown that during sucking, the baby may have EEG patterns of sleep, and at rest, EEG patterns of wakefulness. In this way, it was established that the sleep of a newborn is 16.3 hours (instead of the considered 22 hours). The longest uninterrupted period of sleep lasts 4 hours, and the ratio of the duration of night sleep to the duration of daytime is expressed by the ratio of 100:98. Already in the third week of life night sleep is 14.8 hours. The longest period of uninterrupted sleep reaches 8.48 hours, and the ratio of nighttime sleep to daytime sleep is 100:46. A very responsible age for children is 5-6 years of age, when they first switch to myophasic sleep, that is, they divide the day into two periods: sleep and wakefulness. The body prepares for this gradually, gradually moving from multiple periods of daytime sleep to a single daytime sleep, until it completely leaves polyphasic sleep.
Change of sleep and wakefulness at different ages
1 - newborn; 2 - 1-2 years; 3 - 4 years; 4 - 10 years; 5 - adult
In adolescence, sleep is indeed somewhat longer than in adulthood, when individual characteristics and sleep habits are finally formed. It should be firmly remembered that no averages can reflect the many variations in normal sleep duration. In an adult, they range from 4 to 10 hours. These fluctuations have to be taken into account when assessing the individual characteristics of established sleep habits.
It should be emphasized that too much sleep is harmful. The subjective need for prolonged sleep often does not reflect the true need for it, being only the result of a habit, often formed in childhood. Excessive sleep in a child contributes to the development of phlegm, retards mental development, disrupts the functions of blood circulation and digestion.
The German philosopher Immanuel Kant believed that whoever sees in a dream a pleasure or a means to kill time and gives him more than a third of his life or even sleeps a little during the day, he does not know how to evaluate the life assigned to him either qualitatively or quantitatively. The same ideas were reflected in Russian proverbs: “He who sleeps the most, lives the least”, “Sleep a lot - live a little: what is overslept is lived”. Eumeus, the divine swineherd, tells Odysseus: "It is harmful to sleep too much." In the old guides on sleep, the position was expressed that the poorer the mental content, the easier it is to part with it, the easier sleep will come.
People with reduced intelligence and people who are at a low level of development sleep a lot. Miklukho-Maclay noticed that the Papuans sleep a lot and fall asleep in any position. The same can be said about inactive, inert people, such as Oblomov described by Goncharov. “Drowsy and lazy,” testifies folk wisdom. It was really noticed that people who are energetic, mobile, living a tense inner life, sleep less than the average norm. First of all, these are scientists and prominent politicians. (We will return to this issue in the chapter on sleep and wakefulness disorders.) It is noted that older people who have retained a good intellectual form have shorter sleep than those who have lost it. It should be noted that there are a large number of deviations from the above regularity. And yet, it is hardly necessary to consider the deviation of the duration of sleep in the direction of lengthening as useful.
It is necessary to take into account the peculiarities of the sleep of the elderly, which are characterized by a moderate decrease in the total time of night sleep, an increase in the number of awakenings, a decrease in the proportion of the deepest stage of non-REM sleep, and a moderate decrease in REM sleep. (The duration of REM sleep in the elderly is evenly distributed between the first and second halves of the night.)
In addition to age and habit, sleep duration can be influenced by a number of external factors and environmental conditions. Hard work, accompanied by a full-fledged feeling of mental and physical fatigue, contributes to the lengthening of sleep, on the other hand, inactivity also leads to this (for example, during the vacation period).
In the past, people in the countryside slept more than in the city (mainly in winter period). Now, electrification, televisions, the Internet, and, finally, the growth of the cultural level of people living in the countryside have practically erased these differences. However, the working conditions caused a relatively shortened sleep period in the summer during field work compared to the rest of the year.
One of the factors affecting the duration of sleep is also the external temperature. Sleep causes both high and low temperature. In the most acute form, this is observed in cases of the onset of irresistible prolonged sleep in conditions of cooling, during Arctic expeditions. In James Aldridge's novel The Son of a Foreign Land, the onset of sleep in the desert is described under the influence of heat.
All of the above indicates that the influence of environmental factors is also superimposed on the habit developed by a person for a certain duration of sleep.
As already mentioned, from the age of 5-6 years, sleep is monophasic. However, in most southern countries it is common practice to sleep 2-3 hours during the day, as a result of which people get up earlier and go to bed late. This custom is caused by the difficulty of working during the hottest period of the day. It is not advisable to object to this custom, since such a sleep formula has been developed for thousands of years and has undeniable meaning.
The habit of daytime sleep is widespread in all civilized countries. US President Harry Truman publicly stated that he outlived all the members of his cabinet, as he never denied himself a daytime sleep. Winston Churchill regularly slept during the day, while he went to bed naked. Some well-known scientists do the same, if they have at their disposal no more than 20-30 minutes. In their opinion, only such a dream brings the necessary rest.
Solving the question of whether it is useful to sleep during the day is very difficult. In ancient times, afternoon naps were not allowed. Eastern wisdom says that daytime sleep should not last more than 60 breaths, i.e. more than 4 minutes. Despite such definite statements, it is impossible to resolve the issue unambiguously. Based on a number of considerations, it is inappropriate to systematically add another 1-2 hours of daytime sleep to 8 hours of sleep at night. It should be borne in mind that daytime sleep falls on the hours of the daily rhythm, characterized by maximum performance - this is also a lack of daytime sleep. On the other hand, apparently, it is necessary for people who are accustomed to daytime sleep. There are considerations for and against daytime sleep - everyone should decide this issue on their own, general recommendations does not exist here.
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Tuva State University
Faculty of Philology
Sleep and wakefulness.
Completed by: 1st year student
3 groups Mongush Aldynmaa
Checked by: Kuular A.S.
Kyzyl - 2012
Mechanisms of sleep and wakefulness of the body……………………………….3
The role of humoral factors and the occurrence of sleep………………………..4
The meaning of sleep……………………………………………………………………..6
Conclusion………………………………………………………………………7
References ...………………………………………………………………8
The mechanisms of sleep and wakefulness of the body
Any activity of the body takes place against the background of a certain activity of brain structures. The background activity of the brain structures, on which any activity of the body is superimposed, is called the functional state. This activity depends on a set of circumstances: the time of day, the previous activity, the involvement of motivational processes, and so on. Traditionally, researchers have identified two main functional states of the body - sleep and active wakefulness. Initially, it was assumed that these two functional states differ in the level of brain activation, and it was assumed that sleep is due to its decrease, and wakefulness is due to its increase. But after it was proved that sleep is a special functional state with a specific pattern of activity of brain structures peculiar only to it, such a division of these states according to the magnitude of the activation level became incorrect.
The state of wakefulness is the result of the body's active adaptation to the changing conditions of existence. It depends on a person's ability to fix external and internal signals (perception), on his desires (motivational sphere), on the tasks and goals that he defines for himself (cognitive sphere) and on his ability to move around (motor sphere). All these processes, proceeding against the background of the state of wakefulness, are themselves actively involved in its change.
Many processes in the body occur rhythmically. The sleep-wake cycle constantly adjusts to external sensors (length of day and night) and is 24 hours. Synchronously, other rhythms of the body are tuned to him - hormonal, biochemical, physiological, emotional, behavioral. Under natural conditions, the biological clock is regularly synchronized with the day-night cycle.
Sleep is a physiological state, which is characterized primarily by the loss of active mental connections of the subject with the world around him. Sleep is characterized primarily by the loss of active consciousness. A deep sleeper does not respond to many environmental influences unless they are of excessive strength. Reflex reactions during sleep are reduced. Another indicator of the state of sleep is the loss of the ability to actively purposeful activity.
The role of humoral factors and the occurrence of sleep.
Sleep is a physiological need of the body. It takes up about 1/3 of a person's life. During sleep, a number of changes are observed in the physiological systems of a person: there is no consciousness and reactions to many environmental stimuli, motor reflex reactions are sharply reduced, and the conditioned reflex activity of the body is completely inhibited. Significant changes in the activity of vegetative functions were found: the heart rate and blood pressure decrease; breathing becomes more rare and superficial; the intensity of metabolism decreases and the body temperature decreases slightly; the activity of the digestive system and kidneys decreases. During deep sleep, there is a decrease in muscle tone. In a sleeping person, most of the muscles completely relax.
The scientific study of the physiological mechanisms of sleep began in the middle of the 19th century. To date, many different theories have been created, which can be summarized in two main groups.
1. The first group includes the so-called humoral theories of sleep, linking the occurrence of sleep with the accumulation of certain chemicals in the body's blood - hypnotoxins.
Chemical theory. According to this theory, easily oxidized products accumulate in the cells of the body during wakefulness, as a result, oxygen deficiency occurs, and a person falls asleep. According to the psychiatrist E. Claparede, we fall asleep not because we are poisoned or tired, but in order not to get poisoned and not get tired.
However, in recent years, the work of P. K. Anokhin and colleagues has proved that humoral factors play a secondary role. In particular, in observations of conjoined so-called Siamese twins, who had only a common blood circulation, it was found that their sleep does not occur simultaneously. One twin can sleep while the other stays awake. If the main cause of sleep was the accumulation in the blood of hypnogenic substances, i.e., sleep-inducing substances, then both Siamese twins would sleep at the same time.
The chemical theory cannot answer a number of questions either. For example, why does daily poisoning with fatigue products not bring any harm to the body? What happens to these substances in insomnia?
2. As a result of objective criticism, humoral theories of sleep have receded into the background, and theories that explain the emergence of sleep by changes in the activity of the nervous system are now more popular.
Among these neurogenic theories, IP Pavlov's cortical theory was of particular importance. The study of the processes of inhibition in CCM allowed him to suggest that sleep is also a kind of inhibitory process that has spread "entirely to the entire mass of the hemispheres and to the lower parts of the brain" .
The meaning of sleep
Sleep contributes to the processing and memorization of information. During sleep, the mobilization of memory mechanisms is facilitated, since the external information load caused by noise interference and other factors is reduced. During REM (paradoxical) sleep, secondary information is excluded from memory. REM sleep and dreams are necessary for adaptation to informationally meaningful information. The fast phase of sleep also contributes to the improvement of mnestic processes. In addition, it is shown that sleep (when the mind does not control the intellect) is necessary condition enabling intuition. During sleep, poets, composers, scientists can activate creative processes, the results of which are reflected in dreams. It should be emphasized that the stimuli that act in a dream are reflected in a peculiar way in the content of dreams. The stronger and more significant an internal or external stimulus for a person, the less expressive or emotional the content of the dream will be, and vice versa. Weak stimuli, such as long-forgotten impressions, neutral remnants of impressions, weak external stimuli during sleep, are represented in dreams with very impressive pictures, and strong impressions of the previous day or strong external stimuli are often not presented in dreams at all.
During sleep, there is a compensation for the mismatches of cognitive, mnestic, emotional and other that occur during wakefulness. mental processes. The authors believe that segments of sleep stages are important elements reflecting the functionality of sleep and the brain as a whole. Internal organization sleep is determined by the fact that the brain needs to recreate lost ones, debug existing ones and create various options in the system of interneuronal interaction, changed during the period of previous wakefulness. The appointment of sleep as a debugging mechanism, in which the coordination of interneuronal and intersystem interaction is worked out, is aimed at restoring order in the activity of the brain. The transformation of sleep into relative chaos under conditions real life Moreover, stress and insomnia can be the cause of disruption of the sleep structure.
Conclusion
Sleep is a physiological state, which is characterized by the loss of active mental connections of the subject with the world around him. Sleep is vital for higher animals and humans. For a long time, it was believed that sleep is a rest necessary to restore the energy of brain cells after active wakefulness. However, it turned out that brain activity during sleep is often higher than during wakefulness. It was found that the activity of neurons in a number of brain structures during sleep increases significantly, that is, sleep is an active physiological process.
In the twentieth century, our knowledge of the world of sleep has grown tremendously. Freud's recognition and analysis of the meaning of dreams, the discovery of the connection between rapid eye movements and dreams made by Azerinsky and Kleitman, the ongoing work on the study of brain chemistry, hormonal activity during sleep - all these important discoveries bring us closer to a deeper understanding of the physiological and psychological mechanisms of sleep.
The meaning of sleep……………………………………………………………………..6
Conclusion………………………………………………………………………7
References...……………………………………………………………8
The rhythm of sleep is due to many reasons. Some birds and animals, for example, sleep during the day and hunt at night. People who fall into the dungeon, out of necessity, have to change their “habits”. It is easier for the younger ones. Night shift workers in most cases are also reorganized according to the “new schedule”. And in general, after the appearance of electricity, the regime common to all undergoes certain changes: the day lengthens due to artificial lighting and the night shortens, which means that the period of wakefulness increases.
A person sleeps for about a third of his life. If you sleep on average not 8, but only 2 hours a day, then another 17 years are added to 70 years. How many interesting and valuable ideas can be realized during this time! However, this is a matter for the future. The secrets of sleep are just beginning to be comprehended. If today someone by an effort of will forces himself to gain time for work at the expense of a night's rest, then in the end he still loses - tired "mechanisms" reduce their performance, or even undergo painful violations.
The causes of fatigue and sleep are still completely unknown. Some researchers believe that fatigue occurs when the reserves of enzymes and catalysts are exhausted, primarily in the neurocellular systems, which leads to a gradual extinction of their activity. The lost reserves can be replenished only due to the development of an inhibitory state, mainly during sleep. Other scientists attribute a leading role to the accumulation in various tissues, especially in muscles, of decay products that poison them and require a “stop” for their removal; it is they who press the brake pedal of wakefulness.
If these reasons remain still under question, then thanks to modern scientific achievements, we can speak more definitely about the physiological mechanisms of sleep. Sleep is not a frozen, motionless state, which simultaneously replaces wakefulness. It depends on the depth and spread of braking. Just as the degree of wakefulness varies, so does the quality of sleep. Between wakefulness and sleep there is, as it were, an intermediate state of relative equilibrium of physiological excitation and inhibition. This state is called prosonic.
When falling asleep, first of all, cells and areas of the cerebral cortex responsible for the second signaling system are subject to inhibition. They are less stable compared to the evolutionarily older areas of the brain responsible for the first signaling system. Separate areas of the cortex and subcortical formations in a falling asleep person still continue their “reflective” activity for some time, but without correction of the higher parts of the brain. As a result of this, “semi-real”, vague, plastic images appear, usually devoid of spatial orientation.
The physiological processes of inhibition never capture the entire cortex. Certain "watchmen" constantly, even with outwardly apparent deep sleep, continue to connect a person with the outside world. They change at different people and in different conditions. A tired mother can sleep among various noises, but as soon as the child cries, she is there.
In animals, sleep is also not completely complete. Watch your sleeping cat. Her ears often move, and as soon as a rustle is heard, reminiscent of the rustle of a mouse, she immediately jumps up.
Observations of huge mollusks with large heads and eight tentacles-legs living in Italy at a marine biological station are very interesting. Sinking to the bottom of the aquarium and going to bed, the mollusk wraps its head with seven tentacles, and raises the eighth “leg” up. She resembles a sentry guarding a sleeping unit. The wrapped head can be touched and pushed - the mollusk does not move. If you touch the eighth tentacle, he immediately wakes up and swims away. The "sentinel point" of the brain is a necessary protective device for all living things.
During deep sleep, not only does the consciousness stop “functioning”, but a complex of changes takes place in the internal organs of a person. The activity of most of them begins to proceed at a "minimal level". Consumed in the waking state the right substances; in a dream, on the contrary, they are assimilated. Blood pressure drops, body temperature drops somewhat, but the digestive organs, liver, pancreas remain in their mode. The beginning of a decrease in muscle activity is well known to each of us, this is, as it were, the first sign of impending sleep - lethargy appears, eyelids, arms, legs become “heavier”. In deep sleep, the muscles are completely relaxed. That is why the hand of a sleeping person hanging from the bed resembles a limply dangling whip.
The need for sleep is different. As a rule, the older a person is, the less time he sleeps. Newborns need to sleep 22 hours a day, the old man - no more than 4-5. This is explained primarily by the fact that a growing, actively expending energy body (especially children) needs a longer rest to replenish lost energy.
Without sleep, people's life can last much less than without water and food - no more than 10 days. In the Middle Ages and in fascist dungeons during the Great Patriotic War sleep deprivation was used as a particularly sophisticated torture.
Of course, speaking of sleep, one cannot say nothing about dreams. According to the figurative expression of I. M. Sechenov, dreams are "an unprecedented combination of past impressions." In them, in a special form, the nervous traces of the experiences that took place “come to life”, that is, the mechanisms of memory and perception manifest themselves in a peculiar way. "Special conditions" depend on the braking to a greater or lesser extent. Chaotic thinking, devoid of coordination of consciousness, is the most general characteristics dreams.
Advances in science recent years with great certainty allow you to establish how a person sleeps. When they say about someone that he sleeps “like the dead”, this is not true. Any person in a dream makes at least 20-60 minor movements, spending 30 seconds out of every hour on this. In the second half of the night, people move more than in the first. Children are more common than adults.
We can assume that there are no people who do not know dreams. Each normal person at night he sees four or five dreams, but he does not always remember them. The American physiologist N. Kleitman, who devoted more than forty years to describing and studying sleep, drew attention to the fact that during the night a sleeping person periodically repeats rapid eye movements. It was possible to register this movement. Electroencephalograms showed that the appearance of increased electrical activity of the brain among slow “sleepy” waves, which was previously interpreted simply as superficial sleep, coincided in time with eye movement. This led Kleitman and his collaborators to believe that increased electroencephalographic activity and eye movements could be due to the same cause - dreaming. To confirm this assumption, many researchers in different countries made careful observations. Sleeping subjects were awakened immediately after recording a series of eye movements and asked if they had seen
The objective method of studying dreams made it possible to identify a number of patterns in their occurrence. It turned out that dreams begin only after a certain period of deep sleep, when a stable “sleepy” rhythm is recorded on electroencephalograms. Then they appear almost regularly with an interval of about an hour and a half. The first dream does not last long, the next ones gradually increase, and the last one can take more than an hour.
There are frequent cases when a person “in a dream” decides what he could not solve during the day, remembers what he could not remember the day before, even creates what did not work out before. For example, A. S. Pushkin “composed” some poems in a dream and, waking up, immediately wrote them down. A. S. Griboedov's plan "Woe from Wit" also matured during a night's sleep. The famous chemist Kekule in a dream was the first to formulate benzene. I. S. Turgenev, L. N. Tolstoy, A. P. Chekhov wrote about creative “insights” in a dream. Such “whims” of creativity, which idealists tenaciously hold on to, proving the influence of both the unconscious and the supernatural (most often divine) beginnings on the conscious activity of a person, are quite understandable. Any question that seems to “clear up” before us in a dream, on the eve, sometimes not only on this day, but also for many weeks or months, occupied and excited the brain. The decision matured gradually, but could not be finalized, something interfered, including insufficient concentration of attention in connection with the various tasks that had to be carried out. During sleep, a person is freed from stimuli, many areas of the cortex are inhibited, and the last thing to “go to rest” are especially excited ideas on an interesting and tormenting issue. They're leaving, but they haven't left yet. And here, in a half-asleep state, sometimes they create best conditions to solve the problem. And Pushkin, and Griboyedov, and Kekule relentlessly, with inspiration, thought, nurtured their ideas and fell asleep, of course, with thoughts about them, until one day a clear solution was born in a muffled sleep consciousness. Don't be strenuous preparatory creative work happy creative dreams would never be possible.
The content of dreams is greatly influenced by the environment. A broken bottle of pungent perfume in a room often induces sleep with the smell of cologne. Random street noises penetrating through the window, a neighbor's measured snore, the sound of a ticking clock - all this can serve as a stimulus for "sleep symphonies", winds and screams. One day, the faces of a large group of test subjects were splashed with water. Waking up, they said that some dreamed of how they swim, others saw themselves in the shower. Such a dependence of the plot of dreams on the situation once again confirms that wakefulness and sleep are only two interrelated aspects of one physiological process.
People have long tried to interpret dreams and see prophetic predictions in them. AT pre-revolutionary Russia, and even now in some countries "guides-whether" - "dream books" are published. But the interpretation of dreams ultimately depends on their content, and the content cannot be anything other than the product of processing by the brain of signals from external and internal (located in different parts of the body) stimuli and from the pantry of memory. So looking for indications of the future in "sleepy thoughts" is at least ridiculous.
Are dreams helpful or harmful? This question can be answered differently - they are necessary. The scientists did the following experiment. As soon as the examined persons began to move their eyes in their sleep, they were awakened; the control group was awakened only after the completion of the "sleep" cycles. An interesting pattern was observed in people with interrupted dreams - breaks arose more and more often. One of the subjects on the eighth night of the experiment had about 200 cycles of dreams. Nothing like this happened in the control group. However, that's not all. People who were deprived of sleep became irritable, nervous, and their appetite changed after a few days. Obviously, for normal life, the body needs a certain amount of dreams.
Kamenskov M. Yu.
Sleep physiology
Human behavior during sleep
The awake person interacts with environment, responding to external stimuli with adequate reactions, and during sleep this connection with the outside world is interrupted, but does not disappear completely. A sleeping person can wake up under the influence of external stimuli, the most important ones that carry biological significance. However, loud noise, which is of no great importance, does not cause the awakening of the sleeper, although it disrupts the sequence of phases and, as a result, adversely affects sleep. During sleep, the brain does not work at some constant level. The degree of directed attention of a sleeping person changes; in this regard, sleep is divided into several stages; The indicators of each stage is the depth of sleep, measured as the threshold strength required to wake up.
There are the following stages of sleep:
1. Relaxed wakefulness (alpha rhythms with variable amplitude predominate on the EEG) (Fig. 1).
2. Stage A sleep: alpha rhythm gradually disappears. Small theta waves appear at long intervals.
3. Stage B of sleep: this is the stage of falling asleep; characteristic - theta waves, high-amplitude vertex teeth lasting 3-5 s. A person does not distinguish between weak external stimuli.
4. Stage C sleep: superficial sleep. Characterized by spindle-shaped bursts of the beta rhythm and K-complexes.
5. Stage D sleep: moderately deep sleep. Delta waves are recorded with a frequency of 3 - 3.5 Hz.
6. Stage E sleep: deep sleep. Delta waves with a frequency of 0.7 - 1.2 Hz are characteristic.
7. Before awakening, a person goes through another stage of sleep (REM sleep), characterized by EEG desynchronization and episodes of rapid eye movements (Fig. 2). In addition, twitching of the fingers is observed.
Throughout the night, the sequence of stages is repeated about 5 times. The depth of sleep at the same time decreases in the morning.
With age, the ratio between the time of wakefulness and sleep, and also between the last phase of sleep and the remaining 6 stages of sleep changes: there is a gradual decrease in the duration of sleep, a shortening of the last stage of sleep.
A significant proportion of REM sleep in newborns is higher than anyone else. This dream plays an important role in the ontogenetic development of the CNS: infants receive less information from the environment than adults, and their dreams provide internal stimulation that compensates for the lack of external.
There is another classification of sleep stages:
1. Equalizing phase: characterized by an effect on both strong and weak stimuli.
2. Paradoxical phase: strong stimuli cause weaker responses than weak stimuli.
3. Ultradoxal phase: a positive stimulus inhibits, and a negative stimulus causes a conditioned reflex.
4. Narcotic phase: a general decrease in conditioned reflex activity with a much stronger decrease in reflexes to weak stimuli than to strong ones.
5. Inhibitory phase: complete inhibition of conditioned reflexes
Sleep and dreams
It is easier to remember a dream if a person is awakened during the REM sleep phase or after it ends. A person who wakes up during non-REM sleep does not remember dreams, therefore dreams occur during REM sleep; during the latter, sleepwalking, conversation, night terrors in people are observed.
The content of dreams is influenced by previous events: with thirst, REM sleep and dreams become more pronounced. If a person is awakened during the REM phase, then the subsequent stages become longer, dreams are brighter, the body seems to catch up, and no pathological changes occur. External stimuli (especially auditory) fit into the picture of dreams; The connection of these stimuli with the content of the dream is evidence that in non-REM sleep they are more real and more reminiscent of stimuli.
Memory during sleep deteriorates: a person remembers the last dream. But sleep makes it easier to consolidate the material being studied. The material memorized before going to bed is remembered better than the same material learned in the morning or in the afternoon, which is associated
1. Firstly: during the day there are many stimuli that interfere with the process of memorization, in the interval between their memorization and reproduction.
2. Secondly, forgetting can be a violent process that proceeds more slowly during sleep.
Mechanisms of wakefulness and sleep
Differential theory of sleep and wakefulness
In the late 1930s, Bremer discovered that the EEG of a cat with a transection separating the spinal cord from the brain after recovery from surgical shock showed cyclical alternations characteristic of sleep-wake.
If the transection is made at the level of the quadrigemina, that is, sensory stimuli are excluded, except for visual and olfactory ones, an EEG typical of sleep is observed.
Bremer concluded that the CNS is induced and maintained: wakefulness requires a minimum of sensory stimulation, sleep is a state characterized primarily by a decrease in the effectiveness of sensory stimulation of the brain, which confirms the theory of passive wakefulness.
However:
Firstly, in the isolated forebrain, over time, rhythmic fluctuations characteristic of the sleep-wake rhythm appear. In addition, the isolation of a person in a soundproof chamber leads to a decrease in the duration of sleep.
Secondly, data on the influence of the cortex on the state of wakefulness are incorrect, since circadian rhythms of sleep-wake are also observed in newborn children with aencephalics.
Reticular theory of sleep and wakefulness
In the reticular formation of the brain stem there are many neurons, the axons of which go to almost all areas of the brain (except the neocortex). In the late 1940s, Moruzzi and Magun discovered that high-frequency stimulation of the reticular formation of the brainstem of cats causes them to instantly wake up. Damage to the reticular formation causes constant sleep, while interruption of the sensory tracts does not give such an effect.
The reticular formation began to be considered as an area of the brain involved in maintaining sleep. Sleep occurs when its activity falls passively or under the influence of external factors. Activation of the reticular formation depends on the number of sensory impulses entering it, as well as on the activity of descending fibers between the forebrain and stem structures.
However, it was later found that:
1. Firstly: the reticular formation causes not only wakefulness, but also sleep, which depends on the place where the electrodes are applied when it is stimulated by an electrical stimulus.
2. Secondly: the neuronal state of the reticular formation in the waking state and during sleep is not much different.
3. Thirdly: the reticular formation is not the only center of wakefulness: they are also represented in the medial thalamus and in the anterior hypothalamus.
Cortical-subcortical theory
There are reciprocal relationships between the limbic-hypothalamic and reticular structures of the brain. When the limbic-hypothalamic structures of the brain are excited, inhibition of the structures of the reticular formation of the brain stem is observed and vice versa. During wakefulness, due to afferent flows from the sense organs, the structures of the reticular formation are activated, which have an upward activating effect on the cerebral cortex. At the same time, the neurons of the frontal cortex have a descending inhibitory effect on the sleep centers of the posterior hypothalamus, which eliminates the blocking effects of the hypothalamic sleep centers on the reticular formation of the midbrain. With a decrease in the flow of sensory information, the ascending activating influences of the reticular formation on the cerebral cortex decrease. As a result, the inhibitory influences of the frontal cortex on the neurons of the sleep center of the posterior hypothalamus are eliminated, which begin to inhibit the reticular formation of the brain stem even more actively. In conditions of blockade of all ascending activating influences of subcortical formations on the cerebral cortex, a slow-wave stage of sleep is observed.
The hypothalamic centers, due to connections with the limbic structures of the brain, can exert ascending activating influences on the cerebral cortex in the absence of influences from the reticular formation of the brain stem. These mechanisms constitute the cortical-subcortical theory of sleep (P.K. Anokhin), which made it possible to explain all types of sleep and its disorders. It proceeds from the fact that the state of sleep is associated with the most important mechanism - a decrease in the ascending activating influences of the reticular formation on the cerebral cortex. The sleep of non-cortical animals and newborns is explained by the weak manifestation of the descending influences of the frontal cortex on the hypothalamic sleep centers, which under these conditions are in an active state and have an inhibitory effect on the neurons of the reticular formation of the brain stem.
Serotonergic theory of sleep and wakefulness
Two regions were found in the upper parts of the brainstem: the raphe nucleus and the locus coeruleus. The mediator in the cells of the core of the tent is serotonin, and the blue place is norepinephrine.
In the late 1960s, Jouvet came to the conclusion that these two neuronal systems are involved in the occurrence of sleep. Destruction of the suture nuclei in a cat leads to complete insomnia for several days, and sleep is restored over the next few weeks. Partial insomnia may be caused by the suppression of serotonin synthesis by chlorphenylalanine, which can be eliminated by the administration of a serotonin precursor. The destruction of the locus coeruleus leads to the complete disappearance of REM sleep, but does not affect non-REM sleep. Depletion of serotonin stores causes insomnia, and the introduction of serotonin precursors normalizes only slow sleep.
All this suggested that serotonin leads to inhibition of the structures responsible for wakefulness.
It was found that the blue spot suppresses the impulses of the raphe nucleus, and this leads to awakening.
It has now been proven that neurons in the raphe nuclei release serotonin during wakefulness: it serves as a mediator in the process of awakening and as a “sleep hormone” in the waking state: stimulating the release of the sleep substance that induces sleep. The REM sleep phase is provided by the subbluish nucleus.
It was shown that sleep and wakefulness are determined by the activation of specific centers of the brain. One of these centers is the reticular formation, which is located in the brain stem. One of the main components of the reticular formation is the cholinergic nuclei located at the level of the midbrain-pons junction. Neurons of these nuclei have high level activity during wakefulness and REM-phase and inactivated during non-REM sleep.
Other ergic systems of the brain also take part in the regulation of sleep-wakefulness processes, the mediators of which are: serotonin, norepinephrine, histamine, glutamate, vasopressin. It is likely that dyssomnias are caused by dysfunction of neurotransmitter systems.
Endogenous sleep factors
A person feels a certain need for sleep, which is associated with the presence of sleep factors circulating in the blood. Then during sleep their normal concentrations should be restored. It is hypothesized that sleep factors accumulate during wakefulness to sleep-inducing levels. According to another hypothesis, these factors accumulate during sleep: they are formed and released.
From urine and cerebrospinal fluid, a glycopeptide, a delta peptide, has been isolated that induces slow-wave sleep when administered to other animals. There is also a REM sleep factor.
The second hypothesis a led to the discovery in the blood of the delta sleep peptide, which induces deep sleep.
However, the factors found cause sleep in humans and only in some animal species. In addition, it can occur under the influence of other types of substances. To date, it is not known what physiological role the found factors play in the process.
Functional significance of sleep
With prolonged total sleep deprivation up to 116 hours, there are disorders of sleep, behavior, mental processes, affective sphere, the appearance of hallucinations (especially visual ones). The first recovery night was dominated by non-REM sleep, while paradoxical sleep (RS) was observed to disappear, but later there was an increase in PS and an increase in REM sleep.
With deprivation and PS, behavioral disturbances occur, fears and hallucinations appear, however, the effect with deprivation and PS was less significant than with deprivation and non-REM sleep. In subjects who had dreams on the recovery night, there was no compensatory increase in PS. In subjects who experienced behavioral disorders, hallucinations, etc. an increase in PS was observed.
It was found that during deprivation and sleep, the concentration of the delta peptide increases, and its introduction into the thalamus zone caused an increase in slow-wave sleep and PS. The sleep factor, which is used in immunological protection, also accumulates.
According to J. Oswald, slow sleep is needed to restore the efficiency of brain cells. During sleep, it is released from the hypothalamus growth hormone, it is involved in protein biosynthesis in peripheral tissues. The biosynthesis of proteins and RNA in neurons is intensified during PS. According to Labori, slow-wave sleep is associated with the metabolic activity of neuroglia.
J. Moruzzi distinguishes two types of regenerative processes in the nervous tissue.
1. Fast processes: in neurons that perform the function of conducting and synaptic transmission of impulses, these processes last for several seconds, which can also take place during wakefulness, without interrupting the activity of the neuron itself a - sleep is not needed for this.
2. Slow processes are necessary for neurons whose synapses are subject to plastic changes during learning. Perception of all kinds of conscious life that are associated with higher functions. Sleep is not a period of restoration of the entire brain, but only a period of restoration of synapses with plastic properties. In contrast to the "fast" processes, these processes are covered by positive feedback, due to which they maintain their activity, which does not fall off "quickly".
PS is associated with motivational functions: during dreams, the satisfaction of those needs that were not achieved during wakefulness occurs. During sleep, motivational energy is released and, thereby, the state of the body is maintained. In patients with endogenous depression, who are characterized by abnormal vivid dreams, motivational processes are strongly represented during sleep, which leads to a decrease in the severity of these processes during wakefulness. On the other hand, deprivation of REM sleep leads to the severity of motivational processes during wakefulness and reduces the severity of endogenous depression (Vogel). What is the effect of antidepressants
Changes in hormone levels during sleep
|
Hormone |
REM sleep |
NREM sleep |
|
STG |
Decreased concentration |
Increasing concentration |
|
With deprivation and sleep in the second half of the night, the level of growth hormone in the blood, compared with normal, increases. On the same night, when deprivation is made, its level does not change. |
||
|
Prolactin |
Decreased concentration |
Increasing concentration |
|
FSH and LH 1. In adults: |
Decreased concentration |
|
|
2. Puberty: |
Decreased concentration |
Increasing concentration |
|
TSH |
Decreased concentration |
Decreased concentration |
|
ACTH |
Decreased concentration |
Decreased concentration |
|
Cortisol |
Decreased concentration |
Decreased concentration |
|
Catecholamines |
Decreased concentration |
Decreased concentration |
|
With deprivation and an increase in their concentration during sleep. |
||
|
Beta-endorphins, substance P, cAMP, cGMP |
Constant concentration |
Constant concentration |
|
Parathormone |
Increasing concentration |
Increasing concentration |
Sleep and wakefulness. pathological changes.
In 1958-1960found a pattern between sleep duration and mortality. Basically, both short sleepers (4-5 hours a day) and long sleepers (10-12 hours) die from cancer, coronary artery disease, suicides are often committed. Thus, sleep has a restorative effect on both physical and mental health.
Insomnia. Narcolepsy. Hypersomnia.
Insomnia and narcolepsy are hereditary diseases.
Narcolepsy is a wakefulness disorder characterized by daytime attacks of irresistible sleep. It is associated with the fact that a person suffering from narcolepsy, from a state of wakefulness, immediately falls into a paradoxical dream. Symptom - uncontrollable falling asleep, muscle weakness. For many people, the circadian rhythm of sleep-wake is disturbed. Weakness in the muscles appears with anger, laughter, crying and other factors. Hypersomnia is an extraordinary need for sleep, the cause of which is an imbalance in the systems of regulation of sleep-wakefulness in the body.
We see in dreams various combinations of what happened to us during wakefulness: in the cerebral cortex during superficial sleep or during the transition of sleep from one stage to another, when falling asleep, islands remain - uninhibited areas of the cortex, and under the influence of internal or external stimuli any information, events that happened to us in reality are "extracted" from them, which is the basis for the emergence of unreal reality.
During sleep, in our dreams, we see ourselves as ill, and after a few days we actually become ill; the fact is that in a dream we become more sensitive, we feel more acutely the processes that occur in our body, which we feel in reality.
Snore.
Sleep soft tissue rear wall relax and sometimes block the airways (sagging tongue - causes sleep apnea - leads to death) Snoring is a sound generated by soft tissue vibrations, especially the soft palate.
Operations offered:
1. Laser surgery, during which excess tissue is burned
2. A new operation during which electrodes are inserted into the soft palate, it heats the tissue electric shock high frequency, causes them to shrink and returns elasticity in a few weeks.
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