Development of the nervous system after birth. Features of normal development - the nervous system of the child

The nervous system integrates and regulates the vital activity of the whole organism. Its highest department - the brain is an organ of consciousness, thinking.

Mental activity takes place in the cerebral cortex. In the cerebral cortex, new neural connections acquired during life are established, new reflex arcs are closed, and conditioned reflexes are formed (the arcs of congenital, i.e., unconditioned reflexes, take place in the lower parts of the brain and in the spinal cord). In the cerebral cortex, concepts are formed and thinking occurs. Here is the activity of consciousness. The human psyche depends on the degree of development, condition and characteristics of the nervous system and primarily the cerebral cortex. The development of speech and labor activity of a person is closely related to the complication and improvement of activity. cerebral cortex and, at the same time, mental activity.

The subcortical centers closest to the cerebral cortex and the centers of the brain stem carry out complex unconditioned reflex activity, the highest forms of which are instincts. All this activity is under the constant regulatory influences of the cerebral cortex.

Nervous tissue has the property of not only excitation, but also inhibition. Despite their opposites, they always accompany one another, constantly change and pass one into another, representing different phases of a single nervous process. Excitation and inhibition are in constant interaction and are the basis of all activity of the central nervous system. The occurrence of excitation and inhibition depends on the effect on the central nervous system and, above all, on the brain. human environment environment and internal processes occurring in his body. Changes in the external environment or conditions of labor activity cause the emergence of new conditioned connections that are created on the basis of the unconditioned reflexes that a person has or old, strengthened, previously acquired connections, and entail the inhibition of other conditioned connections that, in a new situation, do not have data for their action. When a more or less significant excitation occurs in any part of the cerebral cortex, inhibition occurs in its other parts (negative induction). Excitation or inhibition, having arisen in one or another part of the cerebral cortex, is transmitted further, as if overflowing in order to again concentrate in any one place (irradiation and concentration).

The processes of excitation and inhibition are of great importance in the matter of education and upbringing, since the understanding of these processes and the skillful use of them makes it possible to develop and improve new neural connections, new associations, skills, abilities, and knowledge. But the essence of education and training, of course, cannot be limited to the mere formation of conditioned reflexes, even if they are very subtle and complex. The cerebral cortex of a person has the properties of a versatile perception of the phenomena of the surrounding life, the formation of concepts, their consolidation in the mind (assimilation, memory, etc.) and complex mental functions (thinking). All these processes have the cortex of the cerebral hemispheres as their material substrate and are inextricably linked with all the functions of the nervous system.

In the knowledge of the laws of higher nervous activity (behavior) of animals and humans, the Russian physiological school, represented by its brilliant founders - I. M. Sechenov, N. E. Vvedensky, and especially I. P. Pavlov with their students, made a brilliant contribution. This made possible the materialistic study of psychology.

The development of the nervous system, and primarily the brain, in children and adolescents is of great interest, due to the fact that throughout childhood, adolescence and adolescence, the formation of the human psyche takes place. The formation and improvement of the psyche proceeds on the basis of the development of the cerebral cortex and with its direct participation. By the time of birth, the child's central and peripheral nervous system is far from being developed (especially the cerebral cortex and the subcortical nodes closest to it).

The weight of the brain of a newborn is relatively large, it is 1/9 of the weight of the entire body, while in an adult this ratio is only 1/40. The surface of the cerebral hemispheres in children in the first months of their life is relatively smooth. The main furrows, although outlined, are not deep, and furrows of the second and third categories have not yet formed. The convolutions are still poorly expressed. A newborn has as many nerve cells in the cerebral hemispheres as an adult, but they are still very primitive. Nerve cells in young children are simple spindle-shaped with very few nerve ramifications, and dendrites are just beginning to take shape.

The process of building complexity nerve cells with their processes, i.e., neurons, proceeds very slowly and does not end simultaneously with the completion of the development of other organs and systems of the body. This process continues until the age of 40 and even beyond. Nerve cells, unlike other cells of the body, are not able to multiply, regenerate, and their total number at the time of birth remains unchanged for the rest of life. But in the process of growth of the organism, as well as in subsequent years, nerve cells increase in size, gradually develop, neurites and dendrites lengthen, and the latter, in addition, form tree-like branches as they develop.

Most of the nerve fibers in young children are not yet covered with a white myelin sheath, as a result of which, when cut, the large hemispheres, as well as the cerebellum and medulla oblongata, do not sharply divide into gray and white matter, as occurs in subsequent years.

In functional terms, of all parts of the brain in a newborn, the cerebral cortex is the least developed, as a result of which all life processes in young children are regulated mainly by subcortical centers. As the child's cerebral cortex develops, both perceptions and movements improve, which gradually become more differentiated and complex. At the same time, the cortical connections between perceptions and movements become more and more precise, and the cortical connections between perceptions and movements become more complicated, and the life experience acquired during development (knowledge, skills, motor skills, etc.) begins to show itself more and more.

The maturation of the cerebral cortex occurs most intensively in children during toddler age, that is, during the first 3 years of life. A 2-year-old child already has all the main features of the development of intracortical systems, and the overall picture of the structure of the brain differs relatively little from the brain of an adult. Its further development is expressed in the improvement of individual cortical fields and various layers of the cerebral cortex and an increase in total number myelin and intracortical fibers.

In the second half of the first year of life, the development of conditioned connections in children occurs from all perceiving organs (eyes, ears, skin, etc.) more and more intensively, but still more slowly than in subsequent years. With the development of the cerebral cortex at this age, the duration of periods of wakefulness increases, which favors the formation of new conditioned connections. In the same period, the foundation for future speech sounds is laid, which are associated with certain stimulations and are their external expression. All the formation of speech in children occurs according to the laws of the formation of conditioned reflex connections.

During the second year, simultaneously with the development of the cerebral cortex and the intensification of their activity, more and more new conditioned reflex systems and partly various forms of inhibition are formed in children. The cerebral cortex develops especially intensively in functional terms during the 3rd year of life. During this period, speech develops significantly in children, and by the end of this year, the child’s vocabulary reaches an average of 500.

In the subsequent years of preschool age (from 4 to 6 years old inclusive), children observe the consolidation and further development of the functions of the cerebral cortex. At this age, both analytical and synthetic activity of the cerebral cortex becomes much more complicated in children. Simultaneously, there is a differentiation of emotions. Due to the imitation and repetition inherent in children of this age, which contribute to the formation of new cortical connections, they quickly develop speech, which gradually becomes more complex and improves. By the end of this period, single abstract concepts appear in children.

At primary school age and during puberty, children continue to develop the brain, individual nerve cells improve and new nerve pathways develop, and the entire nervous system develops functionally. At the same time, there is an increase in the growth of the frontal lobes. This entails an improvement in children's accuracy and coordination of movements. In the same period, regulatory control from the side of the cerebral cortex over instinctive and lower emotional reactions is noticeably revealed. In this regard, it acquires special meaning systematic education of children's behavior, diversifying the regulatory functions of the brain.

During puberty, especially towards the end of it - in adolescence, an increase in brain mass is insignificant. At this time, there are mainly processes of complication of the internal structure of the brain. This internal development characterized by the fact that the nerve cells of the cerebral cortex complete their formation, and a particularly vigorous structural development occurs, the final formation of convolutions and the development of associative fibers that connect individual areas of the cortex to each other. The number of associative fibers especially increases in boys and girls aged 16-18 years. All this creates a morphological basis for the processes of associative, logical, abstract and generalizing thinking.

For development and physiological activity the brain during puberty is influenced by the deep changes that occur in the glands internal secretion. Strengthening activities thyroid gland, as well as the sex glands, greatly increases the excitability of the central nervous system and, first of all, the cerebral cortex. “Due to increased reactivity and the resulting instability, especially emotional processes, all adverse environmental conditions: mental trauma, heavy stress, and so on, easily lead to the development of cortical neuroses” (Krasnogorsky). This should be borne in mind by teachers conducting educational work among adolescents and young people.

During adolescence, by the age of 18-20, the functional organization of the brain is basically completed, and the most subtle and complex forms of its analytical and synthetic activity become possible. In subsequent mature years of life, the qualitative improvement of the brain and the further functional development of the cerebral cortex continue. However, the basis for the development and improvement of the functions of the cerebral cortex is laid in children in the preschool and school years.

The medulla oblongata in children is already fully developed and mature in functional terms by the time of birth. The cerebellum, on the contrary, is poorly developed in newborns, its furrows are shallow and the size of the hemispheres is small. From the first year of life, the cerebellum grows very rapidly. By the age of 3, the cerebellum in a child approaches the size of the cerebellum of an adult, in connection with which the ability to maintain body balance and coordination of movements develops.

As for the spinal cord, it does not grow as fast as the brain. However, by the time of birth, the child has sufficiently developed pathways of the spinal cord. Myelination of intracranial and spinal nerves in children it ends by 3 months, and peripheral - only by 3 years. The growth of myelin sheaths continues in subsequent years.

The development of the functions of the autonomic nervous system in children occurs simultaneously with the development of the central nervous system, although from the first year of life it has basically taken shape in terms of functionality.

As you know, the subcortical nodes are the highest centers that unite the autonomic nervous system and control its activity. When, for one reason or another, the controlling activity of the cerebral cortex is upset or weakened in children and adolescents, the activity of the subcortical nodes and, consequently, the autonomic nervous system becomes more pronounced.

As the researchers A. G. Ivanov-Smolensky, N. I. Krasnogorsky and others have shown, the higher nervous activity of children, with all the variety of individual characteristics, has some characteristic features. The cerebral cortex in children of preschool and primary school age is not functionally stable enough. How younger child, the more pronounced is the predominance of excitation processes over the processes of internal active inhibition. Prolonged excitation of the cerebral cortex in children and adolescents can lead to overexcitation and to the development of phenomena of the so-called "outrageous" inhibition.

The processes of excitation and inhibition in children easily radiate, i.e., they spread through the cerebral cortex, which disrupts the functioning of the brain, which requires a high concentration of these processes. Associated with this is the lesser stability of attention and greater exhaustion of the nervous system in children and adolescents, especially in the case of improper organization of educational work, in which there is an excessively large load of mental work. If we take into account that children and adolescents in the process of learning have to significantly strain the activity of the central nervous system, then the need for a particularly attentive hygienic attitude towards the nervous system of students becomes obvious.

Hygiene of the nervous system. For the normal development of the nervous system of children and adolescents, and especially its higher department - the cerebral cortex, the correct organization of the daily regimen, the regulation of mental load, and the correctly delivered physical education, including meaningful, interesting and not excessive physical labor, are of great importance. If children start studying at school at the same hours, prepare homework, if they receive regular food at the same hours, go to bed, get up, if their daily routine is regular, then all processes in the body proceed normally and rhythmically. .

As a result of such a clear regime, children and adolescents develop peculiar conditioned reflexes, and the main stimulus is time. So, when the hour approaches, when the child usually has lunch, he has a feeling of appetite, they begin to stand out digestive juices and thus the organism is prepared for the act of eating. In a similar way, at the usual hour of going to bed in the cortex of the cerebral hemispheres, the processes of inhibition begin to radiate with particular ease, which is precisely what is characteristic of the onset of sleepy state. And in this case, the time is a signal for going to bed, just as the bell is a signal for the upcoming study work in the classroom.

The hygiene of the nervous system of children and adolescents is inextricably linked with the hygienic organization of all educational work. Excessive mental stress in children and adolescents can lead to overwork of the nervous system, which is expressed in fatigue, poor sleep and even insomnia, headaches, increased excitability and irritability, a decrease in the level of mental functions - memory, attention, perception and assimilation. Overwork of the nervous system in children and adolescents is one of the main reasons for the decrease in the body's resistance to infection and other adverse factors. Therefore, the issues of hygiene in educational work and, in particular, teaching hygiene are very important for the normal development of the nervous system of children and adolescents.

The normal development of the nervous system of children and adolescents largely depends on the conditions and influences of their environment. This environment should be such that it excludes moments that irritate and depress the nervous system of children and adolescents. The atmosphere in the school and family should create in them a cheerful state and cheerful mood, so characteristic of healthy, normally developing children. Cleanliness and order, the always benevolent and even treatment of children and adolescents by teachers and parents - all this contributes to a cheerful state of the nervous system and its normal development.

The nervous system of children and adolescents, like all other systems and organs, needs exercise for its comprehensive and complete development (games, exercises in speech, counting, writing, examining, comprehending, etc.). However, these exercises should be moderate, since excessively frequent and, all the more, too persistent tension leads to excessive excitation of the nervous system of children, and this latter invariably entails nervous overwork. Overwork is one of the main factors that inhibit and often distort the development of the nervous system in children and adolescents, especially the cerebral cortex.

For the normal development of the nervous system of children and adolescents, a balanced diet is necessary (consumption of foods containing phosphorus, lecithins, B vitamins, etc.). No less significant is the categorical prohibition of giving children alcoholic beverages, even in moderate doses, since alcohol, which is harmful to all organs, has a particularly harmful effect on the nervous tissue, causing at first excessive excitation of the nervous system, and then a state of decline. With the systematic, at least moderate, use alcoholic beverages degeneration of nerve cells and cerebral vessels can occur, which has a sharply unfavorable effect on mental activity and creates the basis for the development of various nervous diseases.

No less dangerous is tobacco smoking by adolescents. The nicotine contained in it has a harmful effect on the nervous system of adolescents, causing them headaches, nausea, salivation, etc. Therefore, the school and family should work together to prevent teenagers from smoking tobacco and drinking alcohol. The hygiene of the nervous system is the basis, without which the process of normal comprehensive mental and moral formation young man.

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The nervous system regulates the physiological functions of the body in accordance with changing external conditions and maintains a certain constancy of its internal environment at a life-sustaining level. And understanding the principles of its functioning is based on knowledge of the age-related development of the structures and functions of the brain. In the life of a child, the constant complication of the forms of nervous activity is aimed at the formation of an increasingly complex adaptive ability of the organism, corresponding to the conditions of the surrounding social and natural environment.
Thus, the adaptive capabilities of a growing human organism are determined by the level of age organization of its nervous system. The simpler it is, the more primitive its answers, which boil down to simple defensive reactions. But with the complication of the structure of the nervous system, when the analysis of environmental influences becomes more differentiated, the child's behavior also becomes more complicated, and the level of his adaptation increases.

How does the nervous system mature?

In the mother's womb, the embryo receives everything that it needs, is protected from any adversity. And during the period of maturation of the embryo, 25,000 nerve cells are born in its brain every minute (the mechanism of this amazing process is unclear, although it is clear that a genetic program is being implemented). Cells divide and form organs while the growing fetus floats in the amniotic fluid. And through the maternal placenta, he continuously, without any effort, receives food, oxygen, and toxins are removed from his body in the same way.
The nervous system of the fetus begins to develop from the outer germ layer, from which the neural plate, groove, and then the neural tube are first formed. In the third week, three primary cerebral vesicles form from it, two of which (anterior and posterior) divide again, resulting in the formation of five brain bubbles. From each cerebral bladder, various parts of the brain subsequently develop.
Further separation occurs during fetal development. The main parts of the central nervous system are formed: hemispheres, subcortical nuclei, trunk, cerebellum and spinal cord: the main furrows of the cerebral cortex are differentiated; the predominance of the higher parts of the nervous system over the lower ones becomes noticeable.
As the fetus develops, many of its organs and systems conduct a kind of “dress rehearsal” even before their functions become really necessary. So, for example, contractions of the heart muscle occur when there is still no blood and the need to pump it; peristalsis of the stomach and intestines appears, gastric juice, although there is still no food as such; V total darkness eyes open and close; arms and legs move, which gives the mother indescribable joy from the sensation of life emerging in her; a few weeks before birth, the fetus even begins to breathe in the absence of air to breathe.
By the end of the prenatal period, the overall design of the central nervous system reaches almost full development, but the adult brain is much more complex than the brain of a newborn.

Development of the human brain: A, B - at the stage of cerebral vesicles (1 - terminal; 2 intermediate; 3 - middle, 4 - isthmus; 5 - posterior; 6 - oblong); B - the brain of the embryo (4.5 months); G - newborn; D - adult

The brain of a newborn is approximately 1/8 of the body weight and weighs an average of about 400 grams (boys have a little more). By 9 months, the mass of the brain doubles, by the age of 3 it triples, and at the age of 5 the brain is 1/13 - 1/14 of the body weight, by the age of 20 - 1/40. The most pronounced topographic changes in various parts of the growing brain occur in the first 5-6 years of life and end only by the age of 15-16.
Previously, it was believed that by the time of birth, the child's nervous system has a complete set of neurons (nerve cells) and develops only by complicating the connections between them. It is now known that in some formations of the temporal lobe of the hemispheres and the cerebellum, up to 80-90% of neurons are formed only after birth with an intensity that depends on the influx of sensory information (from the sense organs) from the external environment.
The activity of metabolic processes is very high in the brain. Up to 20% of all blood sent by the heart to the arteries of the systemic circulation flows through the brain, which consumes a fifth of the oxygen absorbed by the body. The high speed of blood flow in the cerebral vessels and its saturation with oxygen are necessary primarily for the vital activity of the cells of the nervous system. Unlike the cells of other tissues, the nerve cell does not contain any energy reserves: the oxygen and nutrition supplied with the blood are consumed almost instantly. And any delay in their delivery threatens with danger, when the oxygen supply is stopped for only 7-8 minutes, the nerve cells die. On average, an influx of 50-60 ml of blood is needed per 100 g of medulla in one minute.

The proportions of the bones of the skull of a newborn and an adult

Corresponding to an increase in the mass of the brain, significant changes occur in the proportions of the bones of the skull in the same way as the proportion of body parts changes in the process of growth. The skull of newborns is not completely formed, and its sutures and fontanelles may still be open. In most cases, by birth, a diamond-shaped opening at the junction of the frontal and parietal bones (large fontanelle) remains open, which usually closes only by the age of one, the child’s skull is actively growing, while the head is increasing in circumference.
This happens most intensively in the first three months of life: the head increases in circumference by 5-6 cm. Later, the pace slows down, and by the year it increases by a total of 10-12 cm. Usually in a newborn (weighing 3-3.5 kg ) head circumference is 35-36 cm, reaching 46-47 cm by one year. Further, head growth slows down even more (does not exceed 0.5 cm per year). Excessive growth of the head, as well as its noticeable lag, indicates the possibility of developing pathological phenomena (in particular, hydrocephalus or microcephaly).
With age, the spinal cord also undergoes changes, the length of which in a newborn is on average about 14 cm and doubles by 10 years. Unlike the brain, the spinal cord of a newborn has a functionally more perfect, complete morphological structure, almost completely occupying space spinal canal. With the development of the vertebrae, the growth of the spinal cord slows down.
Thus, even with normal intrauterine development, normal childbirth, a child is born, albeit with a structurally formed, but immature nervous system.

What do reflexes give the body?

The activity of the nervous system is basically reflex. Under the reflex understand the response to the impact of an irritant from the external or internal environment of the body. To implement it, a receptor with a sensitive neuron that perceives irritation is needed. The response of the nervous system comes ultimately to the motor neuron, which reacts reflexively, prompting or “slowing down” the organ innervated by it, the muscle, to activity. Such a simple chain is called a reflex arc, and only if it is preserved can a reflex be realized.
An example is the reaction of a newborn to a slight dashed irritation of the corner of the mouth, in response to which the child turns his head towards the source of irritation and opens his mouth. The arc of this reflex, of course, is more complex than, for example, the knee reflex, but the essence is the same: in response to irritation of the reflexogenic zone, the child develops search head movements and readiness to suck.
There are simple reflexes and complex ones. As can be seen from the example, the search and sucking reflexes are complex, and the knee reflex is simple. At the same time, congenital (unconditioned) reflexes, especially during the neonatal period, are in the nature of automatisms, mainly in the form of food, protective and postural tonic reactions. Such reflexes in humans are provided on different "floors" of the nervous system, therefore, spinal, stem, cerebellar, subcortical and cortical reflexes are distinguished. In a newborn child, taking into account the unequal degree of maturity of the parts of the nervous system, reflexes of spinal and stem automatisms predominate.
In the course of individual development and the accumulation of new skills, conditioned reflexes are formed due to the development of new temporary connections with the obligatory participation of the higher parts of the nervous system. The large hemispheres of the brain play a special role in the formation of conditioned reflexes, which are formed on the basis of innate connections in the nervous system. Therefore, unconditioned reflexes exist not only on their own, but as a constant component they enter into all conditioned reflexes and the most complex acts of life.
If you look closely at the newborn, then the chaotic nature of the movements of his arms, legs, and head attracts attention. The perception of irritation, for example, on the leg, cold or pain, does not give an isolated withdrawal of the leg, but a general (generalized) motor reaction of excitation. The maturation of structure is always expressed in the improvement of function. This is most noticeable in the formation of movements.
It is noteworthy that the first movements in a fetus of three weeks of age (length 4 mm) are associated with heart contractions. A motor reaction in response to skin irritation appears from the second month of intrauterine life, when the nerve elements of the spinal cord are formed, which are necessary for reflex activity. At the age of three and a half months, the fetus can show most of the physiological reflexes observed in newborns, with the exception of screaming, grasping reflex and breathing. With the growth of the fetus and an increase in its mass, the volume of spontaneous movements also becomes large, which can be easily verified by causing the fetus to move by careful tapping on the mother's abdomen.
In the development of a child's motor activity, two interrelated patterns can be traced: the complication of functions and the extinction of a number of simple, unconditioned, innate reflexes, which, of course, do not disappear, but are used in new, more complex movements. The delay or late extinction of such reflexes indicates a lag in motor development.
The motor activity of a newborn and a child in the first months of life is characterized by automatisms (sets of automatic movements, unconditioned reflexes). With age, automatisms are replaced by more conscious movements or skills.

Why do we need motor automatisms?

The main reflexes of motor automatism are food, protective spinal, tonic position reflexes.

Food motor automatisms provide the child with the ability to suck and search for a source of food for him. The preservation of these reflexes in the newborn indicates the normal function of the nervous system. Their manifestation is as follows.
When pressing on the palm, the child opens his mouth, turns or bends his head. If you apply a light blow with your fingertips or a wooden stick on the lips, in response they are drawn into a tube (therefore, the reflex is called proboscis). When stroking in the corner of the mouth, the child has a search reflex: he turns his head in the same direction and opens his mouth. The sucking reflex is the main one in this group (characterized by sucking movements when a nipple, breast nipple, finger enters the mouth).
If the first three reflexes normally disappear by 3-4 months of life, then sucking - by one year. These reflexes are most actively expressed in a child before feeding, when he is hungry; after eating, they may fade somewhat, as a well-fed child calms down.

Spinal motor automatisms appear in a child from birth and persist for the first 3-4 months and then fade away.
The simplest of these reflexes is the defensive reflex: if the child is placed face down on his stomach, he will quickly turn his head to the side, facilitating his breathing through his nose and mouth. The essence of another reflex is that in the position on the stomach, the child makes crawling movements if a support (for example, a palm) is placed on the soles of the feet. Therefore, the inattentive attitude of parents to this automatism can end sadly, since a child left unattended by his mother on the table can, resting his feet on something, push himself to the floor.

Let's check the reflexes: 1 - palmar-mouth; 2 - proboscis; 3 - search; 4 - sucking

The tenderness of parents causes the ability of a tiny man to lean on his legs and even walk. These are support reflexes and automatic walking. To check them, you should lift the child, holding him under the arms, and put him on a support. Feeling the surface with the soles of the feet, the child will straighten the legs and rest against the table. If he is slightly tilted forward, he will take a reflex step with one and then the other foot.
From birth, a child has a well-defined grasping reflex: the ability to hold the fingers of an adult well placed in his palm. The force with which he grasps is sufficient to hold himself, and he can be lifted up. The grasping reflex in newborn monkeys allows the cubs to keep themselves on the mother's body when she moves.
Sometimes parental anxiety is caused by scattering of the child's arms during various manipulations with him. Such reactions are usually associated with the manifestation of an unconditioned grasping reflex. It can be caused by any stimulus of sufficient strength: by patting on the surface on which the child lies, by raising the extended legs above the table, or by quickly extending the legs. In response to this, the baby spreads the arms to the sides and opens the fists, and then returns them to their original position again. With increased excitability of the child, the reflex increases, being caused by stimuli such as sound, light, a simple touch or swaddling. The reflex fades after 4-5 months.

Tonic position reflexes. In newborns and children of the first months of life, reflex motor automatisms associated with a change in the position of the head appear.
For example, turning it to the side leads to a redistribution muscle tone in the limbs so that the arm and leg, to which the face is turned, are unbent, and the opposite ones are bent. In this case, the movements in the arms and legs are asymmetrical. When the head is bent to the chest, the tone in the arms and legs increases symmetrically and leads them to flexion. If the child's head is straightened, then the arms and legs will also straighten due to an increase in tone in the extensors.
With age, at the 2nd month, the child develops the ability to hold his head, and after 5-6 months he can turn from his back to his stomach and vice versa, and also hold the “swallow” position if he is supported (under the stomach) by hand.

Let's check the reflexes: 1 - protective; 2 - crawling; 3 - support and automatic walking; 4 - grasping; 5 - hold; 6 - wraps

In the development of motor functions in a child, a descending type of formation of movement is traced, that is, at the beginning of the movement of the head (in the form of its vertical setting), then the child forms the support function of the hands. When turning from back to stomach, the head first turns, then the shoulder girdle and then the torso and legs. Later, the child masters leg movements - support and walking.

Let's check the reflexes: 1 - asymmetric cervical tonic; 2 - symmetrical cervical tonic; 3 - holding the head and legs in the "swallow" position

When, at the age of 3-4 months, a child, who previously knew how to lean well on his legs and take steps with support, suddenly loses this ability, the anxiety of the parents makes them go to the doctor. Fears are often unfounded: at this age, the reflex reactions of support and the stepping reflex disappear and are replaced by the development of vertical standing and walking skills (by 4-5 months of life). This is how the “program” of mastering movements during the first year and a half of a child’s life looks like. Motor development provides the ability to hold the head by 1-1.5 months, purposeful hand movements - by 3-4 months. At about 5-6 months, the child grasps objects well in his hand and holds them, he can sit and he becomes ready to stand. At 9-10 months, he will already begin to stand with support, and at 11-12 months he can move with outside help and on his own. Uncertain at first, the gait becomes more and more stable, and by 15-16 months the child rarely falls while walking.

The health of the child is the main thing for parents, but in order to take care of the health of your baby, you need to understand how the development of the whole organism as a whole and each system separately proceeds. In this article, we will look at the development of the child's nervous system, as well as possible good and bad sources of influence on it.
The body is a single whole, where organs and systems are interconnected and depend on each other. All activity of the body is regulated by the nervous system, especially its higher department - the cerebral cortex.
The development and activity of the brain, and the nervous system in general, depends on the conditions of life, on education - the decisive factor. Therefore, it is worth paying attention to this not only to you as educators, but also to grandparents.
The newborn is not adapted to independent existence. His movements are not yet formalized. Better movements developed hearing and vision. The newborn has only simple local reflexes, such as sucking, blinking. These are unconditioned (innate) reflexes.
Simultaneously with feeding and caring for the baby, the circumstances accompanying them are repeated many times: the voice of the mother, certain positions of the child, etc. Due to this, through unconditioned reflexes, new, response reactions of the child's body to various stimuli arise. New neural connections are formed, which are called conditioned reflexes.
In the future, the nervous system of the child is gradually improved. Verbal thinking arises in him and physical development progresses, connections are established between speech stimuli and muscle-motor reactions. Associated with this are the manifestations of the child's conscious, "actively imitative" actions. Such actions, representing the highest conditioned reflex activity, are gradually improved under the influence of the environment and education.
Some conditioned reflexes are strengthened and preserved for long years, others fade, slow down. New conditioned reflexes are also formed.
Conscious movements are of great importance in the life of a baby. Conscious movements are subject to the regulatory influence of the cerebral cortex. The development of coordination of movements is associated with the inhibition of unnecessary accompanying movements.
Thus, along with the mastery of the necessary movements, the development of inhibitory processes takes place, which are so important for the formation of the higher nervous activity of the child.
Among the various constantly changing effects on the nervous system, there are those that are repeated with a certain sequence (for example, regime moments). With the repeated repetition of one influence after another, a long chain of conditioned reflexes arises in the brain. A certain routine of activity, rest, sleep, and eating becomes habitual for the child. So he learns to obey.

A good state of the nervous system is the key to the health of the crumbs, his mental and moral development.

It is necessary to carefully protect the nervous system of children.

Proper development of the child's nervous system

What needs to be done so that the development of the baby's nervous system proceeds properly?
For this, it is necessary, firstly, to take care of the hygiene of their life. It is known, for example, beneficial effect fresh air for brain function. In families where it is installed, an appropriate one is organized, the right child of this age is provided restful sleep(without

The nervous system coordinates and controls the physiological and metabolic parameters of the body's activity, depending on the factors of the external and internal environment.

In the child's body, the anatomical and functional maturation of those systems that are responsible for vital activity takes place. Assuming up to 4 years mental development the child is most intense. Then the intensity decreases, and by the age of 17 the main indicators of neuropsychic development are finally formed.

By the time of birth, the baby's brain is underdeveloped. For example, a newborn has about 25% of the nerve cells of an adult, by 6 months of life their number increases to 66%, and by the year - up to 90-95%.

Different parts of the brain have their own pace of development. So, the inner layers grow more slowly than the cortical, due to which folds and furrows form in the latter. By the time of birth, the occipital lobe is better developed than others, and the frontal lobe is to a lesser extent. The cerebellum has small hemispheres and superficial grooves. The lateral ventricles are relatively large.

How less age of a child, the worse differentiated is the gray and white matter of the brain, the nerve cells in the white matter are located quite close to each other. With the growth of the child, changes in the topic, shape, number and size of the furrows occur. The main structures of the brain are formed by the 5th year of life. But even later, the growth of convolutions and furrows continues, however, at a much slower pace. The final maturation of the central nervous system (CNS) occurs by the age of 30-40.

By the time of the birth of a child, in comparison with body weight, it has a relatively large size - 1/8 - 1/9, at 1 year this ratio is 1/11 - 1/12 to 5 years - 1/13-1/14 and in an adult - approximately 1/40. At the same time, with age, the mass of the brain increases.

The process of development of nerve cells consists in the growth of axons, an increase in dendrites, the formation of direct contacts between the processes of nerve cells. By the age of 3, a gradual differentiation of the white and gray matter of the brain occurs, and by the age of 8, its cortex approaches the adult state in structure.

Simultaneously with the development of nerve cells, the process of myelination of nerve conductors takes place. The child begins to acquire effective control over motor activity. The process of myelination as a whole ends by 3-5 years of a child's life. But the development of myelin sheaths of conductors responsible for fine coordinated movements and mental activity continues up to 30-40 years.

The blood supply to the brain in children is more abundant than in adults. The capillary network is much wider. The outflow of blood from the brain has its own characteristics. Diploetic foams are still poorly developed, therefore, in children with encephalitis and cerebral edema, more often than in adults, there is a difficulty in the outflow of blood, which contributes to the development toxic injury brain. On the other hand, children have a high permeability of the blood-brain barrier, which leads to the accumulation of toxic substances in the brain. The brain tissue in children is very sensitive to increased intracranial pressure, so factors contributing to this can cause atrophy and death of nerve cells.

They have structural features and membranes of the child's brain. How younger child, the thinner the dura mater. It is fused with the bones of the base of the skull. The soft and arachnoid shells are also thin. Subdural and subarachnoid spaces in children are reduced. Tanks, on the other hand, are relatively large. The aqueduct of the brain (Sylvian aqueduct) is wider in children than in adults.

With age, a change in the composition of the brain occurs: the amount decreases, the dry residue increases, the brain cells are filled with a protein component.

The spinal cord in children is relatively better developed than the brain, and grows much more slowly, doubling its mass occurs by 10-12 months, tripling - by 3-5 years. In an adult, the length is 45 cm, which is 3.5 times longer than in a newborn.

The newborn has features of CSF formation and CSF composition, the total amount of which increases with age, resulting in increased pressure in the spinal canal. With spinal puncture, CSF in children flows out in rare drops at a rate of 20-40 drops per minute.

Of particular importance is the study of cerebrospinal fluid in diseases of the central nervous system.

Normal cerebrospinal fluid in a child is transparent. Turbidity indicates an increase in the number of leukocytes in it - pleocytosis. For example, cloudy cerebrospinal fluid is observed with meningitis. With a hemorrhage in the brain, the cerebrospinal fluid will be bloody, stratification does not occur, it will retain a uniform brown color.

Under laboratory conditions, a detailed microscopy of the cerebrospinal fluid is carried out, as well as its biochemical, virological and immunological examination.

Patterns of development of statomotor activity in children

A child is born with a number of unconditioned reflexes that help him adapt to his environment. First, these are transient rudimentary reflexes, reflecting the evolutionary path of development from animal to human. They usually disappear in the first months after birth. Secondly, these are unconditioned reflexes that appear from the birth of a child and persist for life. The third group includes mesencephalic established, or automatisms, for example, labyrinthine, cervical and trunk, which are acquired gradually.

Usually, the unconditioned reflex activity of the child is checked by a pediatrician or a neurologist. The presence or absence of reflexes, the time of their appearance and extinction, the strength of the response and the age of the child are assessed. If the reflex does not correspond to the age of the child, this is considered a pathology.

The health worker should be able to assess the motor and static skills of the child.

Due to the dominant influence extrapyramidal system newborn are chaotic, generalized, inappropriate. There are no static functions. Muscular hypertension is observed with a predominance of flexor tone. But shortly after birth, the first static coordinated movements begin to form. At the 2-3rd week of life, the child begins to fix his gaze on a bright toy, and from 1-1.5 months he tries to follow moving objects. By the same time, children begin to hold their heads, and at 2 months and turn it. Then there are coordinated hand movements. At first, this is bringing hands to the eyes, examining them, and from 3-3.5 months - holding the toy with both hands, manipulating it. From the 5th month, one-handed grasping and manipulation of the toy gradually develops. From this age, reaching out and grasping objects resembles the movements of an adult. However, due to the immaturity of the centers responsible for these movements, in children of this age, movements of the second arm and legs occur simultaneously. By 7-8 months, there is a greater expediency of motor activity of the hands. From 9-10 months there is a finger retention of objects, which is improved by 12-13 months.

The acquisition of motor skills by the limbs occurs in parallel with the development of trunk coordination. Therefore, by 4-5 months, the child first rolls over from his back to his stomach, and from 5-6 months from his stomach to his back. In parallel, he masters the function of sitting. At the 6th month, the child sits on his own. This indicates the development of coordination of the muscles of the legs.

Then the child begins to crawl, and by 7-8 months already mature crawling is formed with a cross movement of the arms and legs. By 8-9 months, children try to stand and step over the bed, holding on to its edge. At 10-11 months they already stand well, and by 10-12 months they begin to walk independently, first with their arms extended forward, then their legs straighten and the child walks almost without bending them (by 2-3.5 years). By the age of 4-5, a mature gait with synchronous articulated hand movements is formed.

The formation of statomotor functions in children is a long process. The emotional tone of the child is important in the development of statics and motor skills. In acquiring these skills, a special role is assigned to the independent activity of the child.

The newborn has little physical activity, he mostly sleeps, and wakes up when he wants to eat. But even here there are principles of direct influence on neuropsychic development. From the first days, toys are hung over the crib, first at a distance of 40-50 cm from the child's eyes for the development of the visual analyzer. During the waking period, it is necessary to talk with the child.

At 2-3 months, sleep becomes less prolonged, the child is already awake for more time. The toys are attached at chest level so that after a thousand and one wrong moves, he finally grabs the toy and pulls it into his mouth. The conscious manipulation of toys begins. The mother or caregiver during hygiene procedures begins to play with him, do massage, especially the abdomen, gymnastics for the development of motor movements.

At 4-6 months, the child's communication with an adult becomes more diverse. At this time has great importance and independent activities of the child. A so-called rejection reaction develops. The child manipulates toys, is interested in the environment. There may be few toys, but they should be diverse in both color and functionality.

At 7-9 months, the movements of the child become more appropriate. Massage and gymnastics should be aimed at developing motor skills and statics. Sensory speech develops, the child begins to understand simple commands, pronounce simple words. The stimulus for the development of speech is the conversation of the surrounding people, songs and poems that the child hears during wakefulness.

At 10-12 months, the child gets on his feet, begins to walk, and at this time his safety becomes of great importance. During the wakefulness of the child, it is necessary to securely close all drawers, remove foreign objects. Toys become more complex (pyramids, balls, cubes). The child tries to independently manipulate the spoon and cup. Curiosity is already well developed.

Conditioned reflex activity of children, development of emotions and forms of communication

Conditioned reflex activity begins to form immediately after birth. A crying child is picked up, and he falls silent, makes exploring movements with his head, anticipating feeding. At first, reflexes are formed slowly, with difficulty. With age, the concentration of excitation develops, or the irradiation of reflexes begins. With growth and development, approximately from the 2-3rd week, differentiation of conditioned reflexes occurs. A 2-3-month-old child has a rather pronounced differentiation of conditioned reflex activity. And by 6 months in children, the formation of reflexes from all perceiving organs is possible. During the second year of life, the child's mechanisms for the formation of conditioned reflexes are further improved.

On the 2-3rd week during sucking, taking a break for rest, the child carefully examines the face of the mother, feels the breast or the bottle from which he is fed. By the end of the 1st month of life, the child's interest in the mother increases even more and manifests itself outside the meal. At 6 weeks, the approach of the mother makes the baby smile. From the 9th to the 12th week of life, a rumor is formed, which is clearly manifested when the child communicates with the mother. General motor excitation is observed.

Approaching 4-5 months stranger causes the cooing to stop, the child carefully examines it. Then there is either a general excitement in the form of joyful emotions, or as a result of negative emotions - crying. At 5 months, the child already recognizes his mother among strangers, reacts differently to the disappearance or appearance of the mother. By 6-7 months, children begin to form an active cognitive activity. During wakefulness, the child manipulates toys, often backlash on a stranger is suppressed by the manifestation of a new toy. Sensory speech is being formed, i.e. understanding of the words spoken by adults. After 9 months, there is a whole range of emotions. Contact with strangers usually causes a negative reaction, but it quickly becomes differentiated. The child has timidity, shyness. But contact with others is established due to interest in new people, objects, manipulations. After 9 months, the child's sensory speech develops even more, it is already used to organize his activities. The formation of motor speech is also referred to this time, i.e. pronunciation of individual words.

Speech development

The formation of speech is a stage in the formation of the human personality. Special brain structures are responsible for a person's ability to articulate. But the development of speech occurs only when the child communicates with another person, for example, with his mother.

There are several stages in the development of speech.

Preparatory stage. The development of cooing and babbling begins at 2-4 months.

Stage of occurrence of sensory speech. This concept means the child's ability to compare and associate a word with a specific object, image. At 7-8 months, the child, to the questions: “Where is mom?”, “Where is the kitty?”, - begins to look for an object with his eyes and fix his eyes on it. Intonations that have a certain color can be enriched: pleasure, displeasure, joy, fear. By the year there is already a vocabulary of 10-12 words. The child knows the names of many objects, knows the word "no", fulfills a number of requests.

Stage of occurrence of motor speech. The first words the child pronounces at 10-11 months. The first words are built from simple syllables (ma-ma, pa-pa, uncle-dya). A children's language is being formed: a dog - “av-av”, a cat - “kiss-kiss”, etc. In the second year of life, the child's vocabulary expands to 30-40 words. By the end of the second year, the child begins to speak in sentences. And by the age of three, the concept of “I” appears in speech. More often, girls master motor speech earlier than boys.

The role of imprinting and education in the neuropsychic development of children

In children from the period of the newborn, a mechanism of instant contact is formed - imprinting. This mechanism, in turn, is associated with the formation of the neuropsychic development of the child.

Maternal upbringing very quickly forms a sense of security in a child, and breastfeeding creates a feeling of security, comfort, warmth. The mother is an indispensable person for the child: she forms his ideas about the world around him, about the relationship between people. In turn, communication with peers (when the child begins to walk) forms the concept of social relations, camaraderie, inhibits or enhances the feeling of aggressiveness. The father plays a big role in the upbringing of the child. His participation is necessary for the normal building of relationships with peers and adults, the formation of independence and responsibility for a particular matter, a course of action.

Dream

For full development, the child needs proper sleep. In newborns, sleep is polyphasic. During the day, the child falls asleep from five to 11 times, not distinguishing day from night. By the end of the 1st month of life, the rhythm of sleep is established. Night sleep begins to prevail over daytime. Hidden polyphasic persist even in adults. On average, the need for nighttime sleep decreases over the years.

The decrease in the total duration of sleep in children occurs due to daytime sleep. By the end of the first year of life, children fall asleep once or twice. By 1-1.5 years, the duration of daytime sleep is 2.5 hours. After four years, not all children have daytime sleep, although it is desirable to keep it up to six years.

Sleep is organized cyclically, i.e., the phase of non-REM sleep ends with the phase of REM sleep. Sleep cycles change several times during the night.

In infancy, there are usually no problems with sleep. At the age of one and a half years, the child begins to fall asleep more slowly, so he himself chooses techniques that contribute to falling asleep. It is necessary to create a familiar environment and a stereotype of behavior before going to bed.

Vision

From birth to 3 - 5 years there is an intensive development of eye tissues. Then their growth slows down and, as a rule, ends in puberty. In a newborn, the mass of the lens is 66 mg, in a one-year-old child, 124 mg, and in an adult, 170 mg.

In the first months after birth, children have farsightedness (hypermetropia) and emmetropia develops only by the age of 9-12. The eyes of the newborn are almost constantly closed, the pupils are constricted. The corneal reflex is well expressed, the ability to converge is uncertain. There is nystagmus.

The lacrimal glands do not function. At about 2 weeks, fixation of the gaze on the object develops, usually monocular. From this time, the lacrimal glands begin to function. Usually, by 3 weeks, the child steadily fixes his gaze on the object, his vision is already binocular.

At 6 months, color vision appears, and by 6-9 months, stereoscopic vision is formed. The child sees small objects, distinguishes distance. The transverse size of the cornea is almost the same as in an adult - 12 mm. By the year, the perception of various geometric shapes is formed. After 3 years, all children already have a color perception of the environment.

The visual function of the newborn is checked by bringing a light source to his eyes. In bright and sudden lighting, he squints, turns away from the light.

In children after 2 years, visual acuity, visual field volume, color perception are checked using special tables.

Hearing

The ears of newborns are quite morphologically developed. The external auditory meatus is very short. The dimensions of the tympanic membrane are the same as those of an adult, but it is located in a horizontal plane. Auditory (Eustachian) tubes are short and wide. There is embryonic tissue in the middle ear, which is resorbed (resolved) by the end of the 1st month. The cavity of the tympanic membrane is airless before birth. With the first breath and swallowing movements, it is filled with air. From this moment, the newborn hears, which is expressed in a general motor reaction, a change in the frequency and rhythm of the heartbeat, breathing. From the first hours of life, the child is capable of perceiving sound, its differentiation in frequency, volume, and timbre.

The function of hearing in a newborn is checked by the response to a loud voice, clap, rattle noise. If the child hears, there is a general reaction to, he closes his eyelids, tends to turn towards the sound. From 7-8 weeks of life, the child turns his head towards the sound. Auditory response in older children, if necessary, checked with an audiometer.

Smell

From birth, the perceiving and analyzing areas of the olfactory center have been formed in a child. The nervous mechanisms of smell begin to function from the 2nd to the 4th month of life. At this time, the child begins to differentiate smells: pleasant, unpleasant. Differentiation of complex odors up to 6-9 years occurs due to the development of cortical centers of smell.

The technique for studying the sense of smell in children consists in bringing various odorous substances. At the same time, the child's facial expressions in response to this substance are monitored. It can be pleasure, displeasure, screaming, sneezing. In an older child, the sense of smell is checked in the same way. According to his answer, the safety of the sense of smell is judged.

Touch

The sense of touch is provided by the function of skin receptors. In a newborn, pain, tactile sensitivity and thermoreception are not formed. The perception threshold is especially low in premature and immature children.

The reaction to pain stimulation in newborns is general, a local reaction appears with age. The newborn reacts to tactile stimulation with a motor and emotional reaction. Thermoreception in newborns is more developed for cooling than for overheating.

Taste

From birth, the child has a taste perception. Taste buds in a newborn are relatively large area than an adult. The threshold of taste sensitivity in a newborn is higher than in an adult. Taste in children is examined by applying sweet, bitter, sour and salty solutions to the tongue. According to the reaction of the child, the presence and absence of taste sensitivity is judged.

Nervous system- this is a combination of cells and the structures of the body created by them in the process of evolution of living beings have reached a high specialization in the regulation of adequate vital activity of the body in constantly changing environmental conditions. The structures of the nervous system receive and analyze various information of external and internal origin, and also form the corresponding reactions of the body to this information. The nervous system also regulates and coordinates the mutual activity of various organs of the body in any conditions of life, provides physical and mental activity, and creates the phenomena of memory, behavior, perception of information, thinking, language, and so on.

In functional terms, the entire nervous system is divided into animal (somatic), autonomic and intramural. The animal nervous system, in turn, is divided into two parts: central and peripheral.

(CNS) is represented by the main and spinal cord. Peripheral nervous system (PNS) central department The nervous system combines receptors (sense organs), nerves, ganglia (plexuses) and ganglia located throughout the body. The central nervous system and the nerves of its peripheral part provide the perception of all information from external sense organs (exteroreceptors), as well as from receptors of internal organs (interoreceptors) and from muscle receptors (prorioreceptors). The information received in the CNS is analyzed and transmitted in the form of impulses of motor neurons to the executing organs or tissues, and, above all, to the skeletal motor muscles and glands. Nerves capable of transmitting excitation from the periphery (from receptors) to centers (in the spinal cord or brain) are called sensory, centripetal or afferent, and those that transmit excitation from centers to the executing organs are called motor, centrifugal, motor, or efferent.

The autonomic nervous system (VIS) innervates the work of internal organs, the state of blood circulation and lymph flow, trophic (metabolic) processes in all tissues. This part of the nervous system includes two sections: sympathetic (accelerates vital processes) and parasympathetic (mainly reduces the level of vital processes), as well as a peripheral section in the form of nerves of the autonomic nervous system, which are often combined with nerves of the peripheral CNS into single structures.

The intramural nervous system (INS) is represented by individual connections of nerve cells in certain bodies(for example, Auerbach cells in the walls of the intestines).

As is known, structural unit nervous system is a nerve cell- a neuron that has a body (soma), short (dendrites) and one long (axon) processes. Billions of body neurons (18-20 billion) form many neural circuits and centers. Between the neurons in the structure of the brain are also billions of macro- and microneuroglia cells that perform support and trophic functions for neurons. A newborn baby has the same number of neurons as an adult. The morphological development of the nervous system in children includes an increase in the number of dendrites and the length of axons, an increase in the number of terminal neural processes (transactions) and between neuronal connective structures - synapses. There is also an intensive covering of the processes of neurons with a myelin sheath, which is called the process of myelination of the Body, and all the processes of nerve cells are initially covered with a layer of small insulating cells, called Schwann cells, since they were first discovered by the physiologist I. Schwann. If the processes of neurons have only isolation from Schwann cells, then they are called silent ‘yakitnim and have a gray color. Such neurons are more common in the autonomic nervous system. The processes of neurons, especially axons, to the Schwann cells are covered with a myelin sheath, which is formed by thin hairs - neurolemamas that grow from the Schwann cells and are white. Neurons that have a myelin sheath are called neurons. Myakity neurons, unlike non-myakity neurons, not only have better isolation of the conduction of nerve impulses, but also significantly increase the speed of their conduction (up to 120-150 m per second, while for non-myakity neurons this speed does not exceed 1-2 m per second. ). The latter is due to the fact that the myelin sheath is not continuous, but every 0.5-15 mm it has the so-called intercepts of Ranvier, where myelin is absent and through which nerve impulses jump according to the principle of a capacitor discharge. The processes of myelination of neurons are most intense in the first 10-12 years of a child's life. The development between neural structures (dendrites, spines, synapses) contributes to the development of children's mental abilities: the amount of memory, the depth and comprehensiveness of information analysis grows, thinking arises, including abstract thinking. Myelination of nerve fibers (axons) increases the speed and accuracy (isolation) of the conduction of nerve impulses, improves coordination of movements, makes it possible to complicate labor and sports movements, and contributes to the formation of the final handwriting of the letter. Myelination of the nerve processes occurs in the following sequence: first, the processes of neurons that form the peripheral part of the nervous system are myelinated, then the processes of the own neurons of the spinal cord, medulla oblongata, cerebellum, and later all the processes of neurons of the cerebral hemispheres. The processes of motor (efferent) neurons are myelinated previously sensitive (afferent).

The nerve processes of many neurons are usually combined into special structures called nerves and which in structure resemble many leading wires (cables). More often, the nerves are mixed, that is, they contain processes of both sensory and motor neurons or processes of neurons of the central and autonomic parts of the nervous system. The processes of individual neurons of the central nervous system in the composition of the nerves of adults are isolated from each other by a myelin sheath, which causes isolated transmission of information. Nerves based on myelinated nerve processes, as well as the corresponding nerve processes, called myakitnims. Along with this, there are also non-myelinated nerves and mixed ones, when both myelinated and non-myelinated nerve processes pass as part of one nerve.

The most important properties and functions of nerve cells and the entire nervous system in general are ITS irritability and excitability. Irritability characterizes the ability of an element in the nervous system to perceive external or internal stimuli that can be created by stimuli of a mechanical, physical, chemical, biological and other nature. Excitability characterizes the ability of the elements of the nervous system to move from a state of rest to a state of activity, that is, to respond with excitation to the action of a stimulus of a threshold, or higher level).

Excitation is characterized by a complex of functional and physico-chemical changes occurring in the state of neurons or other excitable formations (muscles, secretory cells, etc.). Namely: the permeability cell membrane for Na, K ions, the concentration of Na, K ions in the middle and outside of the cell changes, the membrane charge changes (if at rest it was negative inside the cell, then it becomes positive when excited, and on the contrary outside the cell). The resulting excitation is able to propagate along the neurons and their processes and even go beyond them to other structures (most often in the form of electrical biopotentials). The threshold of the stimulus is considered to be such a level of its action that is capable of changing the permeability of the cell membrane for Na * and K * ions with all subsequent manifestations of the excitation effect.

The next property of the nervous system- the ability to conduct excitation between neurons due to the elements that connect and are called synapses. Under electron microscope you can consider the structure of the synapse (lynx), which consists of an expanded end of the nerve fiber, has the shape of a funnel, inside which there are oval or round shape that are capable of releasing a substance called a neurotransmitter. The thickened surface of the funnel has presynaptic membranes, while the postsynaptic membrane is contained on the surface of another cell and has many folds with receptors that are sensitive to the mediator. Between these membranes is the synoptic fissure. Depending on the functional orientation of the nerve fiber, the mediator can be excitatory (for example, acetylcholine) or inhibitory (for example, gamma-aminobutyric acid). Therefore, synapses are divided into excitatory and inhibitory. The physiology of the synapse is as follows: when the excitation of the 1st neuron reaches the presynaptic membrane, its permeability for synaptic vesicles increases significantly and they exit into synaptic cleft, burst and secrete a mediator that acts on the receptors of the postsynaptic membrane and causes excitation of the 2nd neuron, while the mediator itself quickly disintegrates. In this way, excitation is transferred from the processes of one neuron to the processes or body of another neuron or to cells of muscles, glands, etc. The speed of synapse response is very high and reaches 0.019 ms. Not only excitatory synapses, but also inhibitory synapses are always in contact with the bodies and processes of nerve cells, which creates conditions for differentiated responses to the received signal. The synaptic apparatus of the CIS is formed in children under 15-18 years of age. postnatal period life. The most important influence on the formation of synaptic structures creates the level of external information. Exciting synapses are the first to mature in a child's ontogeny (the most intense in the period from 1 to 10 years), and later - inhibitory (at 12-15 years). This unevenness is manifested by the features external behavior children; junior schoolchildren little able to restrain their actions, not satisfied, not capable of in-depth analysis of information, concentration of attention, increased emotional and so on.

The main form of nervous activity, the material basis of which is the reflex arc. The simplest double neuron, monosynaptic reflex arc consists of at least five elements: a receptor, an afferent neuron, the central nervous system, an efferent neuron, and an executing organ (effector). In the scheme of polysynaptic reflex arcs between afferent and efferent neurons there is one or more intercalary neurons. In many cases, the reflex arc closes into a reflex ring due to sensory neurons. feedback, which start from the intero-or proprioreceptors of the working organs and signal the effect (result) of the action performed.

The central part of the reflex arcs is formed by nerve centers, which are actually a collection of nerve cells that provide a certain reflex or regulation of a certain function, although the localization of nerve centers in many cases is conditional. Nerve centers are characterized by a number of properties, among which the most important are: one-sided conduction of excitation; delay in the conduction of excitation (due to synapses, each of which delays the impulse by 1.5-2 ms, due to which the speed of movement of excitation everywhere in the synapse is 200 times lower than along the nerve fiber); summation of excitations; transformation of the rhythm of excitation (frequent irritations do not necessarily cause frequent states of excitation); tone of nerve centers (constant maintenance of a certain level of their excitation);

aftereffect of excitation, that is, the continuation of reflex acts after the cessation of the action of the pathogen, which is associated with the recirculation of impulses on closed reflex or neural circuits; rhythmic activity of nerve centers (ability to spontaneous excitations); fatigue; sensitivity to chemicals and lack of oxygen. special property nerve centers is their plasticity (genetically determined ability to compensate for the lost functions of some neurons and even nerve centers, other neurons). For example, after a surgical operation to remove a separate part of the brain, the innervation of parts of the body subsequently resumes due to the sprouting of new pathways, and the functions of the lost nerve centers can be taken over by neighboring nerve centers.

Nerve centers, and manifestations of excitation and inhibition processes on their basis, provide the most important functional quality of the nervous system - coordination of the functions of the activity of all body systems, including under changing environmental conditions. Coordination is achieved by the interaction of the processes of excitation and inhibition, which in children under 13-15 years of age, as mentioned above, are not balanced with the predominance of excitatory reactions. The excitation of each nerve center almost always spreads to neighboring centers. This process is called irradiation and is caused by many neurons that connect separate parts of the brain. Irradiation in adults is limited by inhibition, while in children, especially at preschool and primary school age, irradiation is little limited, which is manifested by the intemperance of their behavior. For example, when a good toy appears, children can simultaneously open their mouths, scream, jump, laugh, etc.

Due to the following age differentiation and the gradual development of inhibitory qualities in children from 9-10 years old, mechanisms and the ability to concentrate excitation are formed, for example, the ability to concentrate, to adequately act on specific irritations, and so on. This phenomenon is called negative induction. Dissipation of attention during the action of extraneous stimuli (noise, voices) should be considered as a weakening of induction and the spread of irradiation, or as a result of inductive inhibition due to the emergence of areas of excitation in new centers. In some neurons, after the cessation of excitation, inhibition occurs and vice versa. This phenomenon is called sequential induction, and it explains, for example, the increased motor activity of schoolchildren during breaks after motor inhibition during the previous lesson. Thus, the guarantee of high performance of children in the classroom is their active motor rest during breaks, as well as the alternation of theoretical and physically active classes.

A variety of external activities of the body, including reflex movements that change and appear in different joints, as well as the smallest muscle motor acts at work, writing, in sports, etc. Coordination in the central nervous system also ensures the implementation of all acts of behavior and mental activity. The ability to coordinate is an innate quality of the nerve centers, but to a large extent it can be trained, which is actually achieved by various forms of training, especially in childhood.

It is important to highlight the basic principles of coordination of functions in the human body:

The principle of a common final path is that at least 5 sensitive neurons from different reflexogenic zones are in contact with each effector neuron. Thus, different stimuli can cause the same appropriate response, for example, the withdrawal of the hand, and it all depends on which stimulus is stronger;

The principle of convergence (convergence of excitation impulses) is similar to the previous principle and consists in the fact that impulses coming to the CNS through different afferent fibers can converge (convert) in the same intermediate or effector neurons, which is due to the fact that on the body and the dendrites of most CNS neurons end with many processes of other neurons, which makes it possible to analyze impulses by value, to carry out the same type of reactions to various stimuli, etc.;

The principle of divergence is that the excitation that comes even to one neuron of the nerve center instantly spreads to all parts of this center, and is also transmitted to the central zones, or to other functionally dependent nerve centers, which is the basis for a comprehensive analysis of information.

The principle of reciprocal innervation of antagonist muscles is ensured by the fact that when the center of contraction of the flexor muscles of one limb is excited, the center of relaxation of the same muscles is inhibited and the center of the extensor muscles of the second limb is excited. This quality of the nerve centers determines cyclic movements during work, walking, running, etc.;

The principle of recoil is that with strong irritation of any nerve center, one reflex quickly changes to another, with the opposite meaning. For example, after a strong bending of the arm, it quickly and strongly extends it, and so on. The implementation of this principle lies at the basis of punches or kicks, at the basis of many labor acts;

The principle of irradiation lies in the fact that a strong excitation of any nerve center causes the spread of this excitation through intermediate neurons to neighboring, even non-specific centers, capable of covering the entire brain with excitation;

The principle of occlusion (blockage) is that with simultaneous stimulation of the nerve center of one muscle group from two or more receptors, a reflex effect occurs, which is less in strength than the arithmetic sum of the reflexes of these muscles from each receptor separately. This arises due to the presence of common neurons for both centers.

The dominant principle is that in the CNS there is always a dominant focus of excitation, which takes over and changes the work of other nerve centers and, above all, inhibits the activity of other centers. This principle determines the purposefulness of human actions;

The principle of sequential induction is due to the fact that the sites of excitation always have neuronal structures inhibition and vice versa. Due to this, after excitation, braking always occurs (negative or negative series induction), and after braking - excitation (positive series induction)

As stated earlier, the CNS consists of the spinal cord and the brain.

Which, during its length, is conditionally divided into 3 I segments, from each of which one pair of spinal nerves departs (31 pairs in total). In the center of the spinal cord there is the spinal canal and gray matter (accumulations of nerve cell bodies), and on the periphery - white matter, represented by processes of nerve cells (axons covered with myelin sheath), which form ascending and descending pathways of the spinal cord between the segments of the spinal cord itself. spinal cord, and between the spinal cord and the brain.

The main functions of the spinal cord are reflex and conduction. In the spinal cord are reflex centers muscles of the trunk, limbs and neck (stretch reflexes, antagonist muscle reflexes, tendon reflexes), posture maintenance reflexes (rhythmic and tonic reflexes), and autonomic reflexes (urination and defecation, sexual behavior). The leading function carries out the relationship between the activity of the spinal cord and the brain and is provided by ascending (from the spinal cord to the brain) and descending (from the brain to the spinal cord) pathways of the spinal cord.

The spinal cord in a child develops earlier than the main one, but its growth and differentiation continue until adolescence. The spinal cord grows most intensively in children during the first 10 years. life. Motor (efferent) neurons develop earlier than afferent (sensory) ones throughout the entire period of ontogenesis. It is for this reason that it is much easier for children to copy the movements of others than to produce their own motor acts.

In the first months of development of the human embryo, the length of the spinal cord coincides with the length of the spine, but later the spinal cord lags behind the spine in growth and in the newborn the lower end of the spinal cord is at level III, and in adults it is at level 1 lumbar vertebra. At this level, the spinal cord passes into a cone and a final thread (consisting partly of nervous, but mainly of connective tissue), which stretches down and is fixed at the level of the JJ coccygeal vertebra). As a result of this, the roots of the lumbar, sacral, and coccygeal nerves have a long extension in the spinal canal around the final thread, thus forming the so-called cauda equina of the spinal cord. In the upper part (at the level of the base of the skull), the spinal cord connects to the brain.

The brain controls the entire life of the whole organism, contains higher nervous analytical and synthetic structures that coordinate the vital functions of the body, provide adaptive behavior and mental activity of a person. The brain is conditionally divided into the following sections: the medulla oblongata (the place of attachment of the spinal cord); the hindbrain, which unites the pons and cerebellum, the midbrain (peduncles of the brain and the roof of the midbrain); the diencephalon, the main part of which is the optic tubercle or thalamus and under the tubercle formations (pituitary gland, gray tubercle, optic chiasm, epiphysis, etc.) the telencephalon (two large hemispheres covered with the cerebral cortex). The diencephalon and telencephalon are sometimes combined into the forebrain.

The medulla oblongata, the pons, the midbrain, and partially the diencephalon together form the brainstem, with which the cerebellum, telencephalon, and spinal cord are connected. In the middle of the brain there are cavities that are a continuation of the spinal canal and are called the ventricles. The fourth ventricle is located at the level of the medulla oblongata;

the cavity of the midbrain is the sylvian strait (aqueduct of the brain); The diencephalon contains the third ventricle, from which the ducts and lateral ventricles depart towards the right and left cerebral hemispheres.

Like the spinal cord, the brain consists of gray (the bodies of neurons and dendrites) and white (from the processes of neurons covered with a myelin sheath) matter, as well as neuroglia cells. In the brain stem, the gray matter is located in separate spots, thus forming nerve centers and nodes. In the telencephalon, gray matter predominates in the cerebral cortex, where the highest nerve centers of the body are located, and in some subcortical regions. The remaining tissues of the cerebral hemispheres and the brain stem are white, representing ascending (to the cortical zones), descending (from the cortical zones) and internal nerve pathways of the brain.

The brain has XII pairs of cranial nerves. At the bottom (base) of the IV-ro ventricle, there are centers (nuclei) of the IX-XII pair of nerves, at the level of the pons of the V-XIII pair; at the level of the midbrain of the III-IV pair of cranial nerves. The 1st pair of nerves is located in the region of the olfactory bulbs contained under the frontal lobes of the cerebral hemispheres, and the nuclei of the 2nd pair are located in the region of the diencephalon.

The individual parts of the brain have the following structure:

The medulla oblongata is in fact a continuation of the spinal cord, has a length of up to 28 mm and in front passes into the varolii of the brain cities. These structures are mainly composed of white matter, forming pathways. The gray matter (the bodies of neurons) of the medulla oblongata and the bridge is contained in the thickness of the white matter in separate islands, which are called nuclei. The central canal of the spinal cord, as indicated, expands in the region of the medulla oblongata and the pons, forming the fourth ventricle, the posterior side of which has a recess - a rhomboid fossa, which in turn passes in Silvio's aqueduct of the brain, connecting the fourth and third - and the ventricles. Most of the nuclei of the medulla oblongata and the bridge are located in the walls (on the bottom) of the IV-ro ventricle, which ensures their better supply of oxygen and consumer substances. At the level of the medulla oblongata and the pons, the main centers of autonomic and, in part, somatic regulation are located, namely: the centers of innervation of the muscles of the tongue and neck ( hypoglossal nerve, XII pairs of cranial nerves); centers of innervation of the muscles of the neck and shoulder girdle, muscles of the throat and larynx (accessory nerve, XI pair). Innervation of the organs of the neck. chest (heart, lungs), abdomen (stomach, intestines), endocrine glands carries out the vagus nerve (X pair),? main nerve of the parasympathetic division of the autonomic nervous system. Innervation of the tongue, taste buds, acts of swallowing, certain parts salivary glands carries out the glossopharyngeal nerve (IX pair). Perception of sounds and information about the position of the human body in space from vestibular apparatus carries out the synovial nerve (VIII pair). The innervation of the lacrimal and part of the salivary glands, the facial muscles is provided by the facial nerve (VII pair). The innervation of the muscles of the eye and eyelids is carried out by the abducens nerve (VI pair). Innervation of masticatory muscles, teeth, oral mucosa, gums, lips, some facial muscles and additional formations the eye is carried out by the trigeminal nerve (V pair). Most nuclei of the medulla oblongata mature in children under 7-8 years of age. The cerebellum is a relatively separate part of the brain, it has two hemispheres connected by a worm. With the help of pathways in the form of lower, middle and upper legs, the cerebellum is connected to the medulla oblongata, the pons and the midbrain. The afferent pathways of the cerebellum come from various parts of the brain and from the vestibular apparatus. The efferent impulses of the cerebellum are directed to the motor parts of the midbrain, the visual tubercles, the cerebral cortex, and to the motor neurons of the spinal cord. The cerebellum is an important adaptive-trophic center of the body; it is involved in the regulation of cardiovascular activity, respiration, digestion, thermoregulation, innervates the smooth muscles of internal organs, and is also responsible for coordination of movements, maintaining posture, and toning the muscles of the body. After the birth of a child, the cerebellum develops intensively, and already at the age of 1.5-2 years, its mass and size reach the size of an adult. The final differentiation of the cellular structures of the cerebellum is completed at the age of 14-15: the ability for arbitrary finely coordinated movements appears, the handwriting of the letter is fixed, and so on. and red core. The roof of the midbrain consists of two upper and two lower hillocks, the nuclei of which are associated with an orienting reflex to visual (upper hillocks) and auditory (lower hillocks) stimulation. The tubercles of the midbrain are called, respectively, the primary visual and auditory centers (at their level, there is a switch from the second to the third neurons in accordance with the visual and auditory tracts, through which visual information is then sent to the visual center, and auditory information to the auditory center of the cerebral cortex) . The centers of the midbrain are closely connected with the cerebellum and provide the emergence of "watchdog" reflexes (return of the head, orientation in the dark, in a new environment, etc.). The substantia nigra and the red core involved in the regulation of posture and body movements maintain muscle tone, coordinate movements during eating (chewing, swallowing). An important function of the red nucleus is the reciprocal (explained) regulation of the work of the antagonist muscles, which determines the coordinated action of the flexors and extensors of the musculoskeletal system. Thus, the midbrain, together with the cerebellum, is the main center for regulating movements and maintaining a normal body position. The cavity of the midbrain is the Sylvian Strait (aqueduct of the brain), at the bottom of which are the nuclei of the block (IV pair) and oculomotor (III pair) cranial nerves that innervate the muscles of the eye.

The diencephalon consists of the epithalamus (nadgirya), thalamus (hills), mesothalamus and hypothalamus (pidzhirya). Epitapamus is combined with the endocrine gland, which is called the pineal gland, or the pineal gland, which regulates the internal biorhythms of a person with environment. This gland is also a kind of chronometer of the body, which determines the change of periods of life, activity during the day, during the seasons of the year, restrains up to a certain period puberty such others. The thalamus, or visual tubercles, unites about 40 nuclei, which are conditionally divided into 3 groups: specific, nonspecific and associative. Specific (or those that switch) nuclei are designed to transmit visual, auditory, skin-muscular-articular and other (except olfactory) information in ascending projection paths to the corresponding sensory zones of the cerebral cortex. Descending paths everywhere specific nuclei transmit information from the motor areas of the cortex to the underlying parts of the brain and spinal cord, for example, in the reflex arcs that control the work skeletal muscle. Associative nuclei transmit information from specific nuclei of the diencephalon to the associative regions of the cerebral cortex. Nonspecific nuclei form the general background of the activity of the cerebral cortex, which maintains a vigorous state of a person. With a decrease in the electrical activity of nonspecific nuclei, a person falls asleep. In addition, it is believed that the nonspecific nuclei of the thalamus regulate the processes of non-voluntary attention and take part in the processes of consciousness formation. Afferent impulses from all receptors of the body (with the exception of olfactory ones), before reaching the cerebral cortex, enter the nuclei of the thalamus. Here, the information is primarily processed and encoded, receives emotional coloring and then goes to the cerebral cortex. The thalamus also has a center of pain sensitivity and there are neurons that coordinate complex motor functions with autonomic reactions (for example, coordination of muscle activity with activation of the heart and respiratory system). At the level of the thalamus, a partial decussation of the optic and auditory nerves is carried out. Cross (chiasm) healthy nerves located in front of the pituitary gland and sensitive optic nerves (II pair of cranial nerves) come here from the eyes. The crossover lies in the fact that the nerve processes photosensitive receptors the left halves of the right and left eyes unite further into the left optic tract, which, at the level of the lateral geniculate bodies of the thalamus, switches to the second neuron, which, through the visual tubercles of the midbrain, is directed to the center of vision, located on the medial surface of the occipital lobe of the cortex of the right hemisphere of the brain. At the same time, neurons from receptors in the right halves of each eye create the right visual tract, which goes to the center of vision of the left hemisphere. Each optic tract contains up to 50% of the visual information of the corresponding side of the left and right eyes (for details, see Section 4.2).

The intersection of the auditory pathways is carried out similarly to the visual ones, but is realized on the basis of the medial geniculate bodies of the thalamus. Each auditory tract contains 75% of the information from the ear of the corresponding side (left or right) and 25% of the information from the ear of the opposite side.

Pidzgirya (hypothalamus) is part of the diencephalon, which controls autonomic reactions, i.e. carries out the coordinative-integrative activity of the sympathetic and parasympathetic divisions of the autonomic nervous system, and also ensures the interaction of the nervous and endocrine regulatory systems. Within the hypothalamus, 32 nerve nuclei are charged, most of which, using nerve and humoral mechanisms, which carry out a kind of assessment of the nature and degree of homeostasis disorders (the constancy of the internal environment) of the body, and also form "teams" that can influence the correction of possible shifts in homeostasis both through changes in the autonomic nervous and endocrine systems, and (through the central nervous system) by changing behavior organism. Behavior, in turn, is based on sensations, of which those associated with biological needs are called motivations. Feelings of hunger, thirst, satiety, pain, physical condition, strength, sexual needs are associated with centers located in the anterior and posterior nuclei of the hypothalamus. One of the largest nuclei of the hypothalamus (gray tubercle) is involved in the regulation of the functions of many endocrine glands (through the pituitary gland), and in the regulation of metabolism, including the exchange of water, salts and carbohydrates. The hypothalamus is also the center of body temperature regulation.

The hypothalamus is closely related to the endocrine gland- the pituitary gland, forming the hypothalamic-pituitary pathway, due to which, as mentioned above, the interaction and coordination of the nervous and humoral systems of regulation of body functions is carried out.

At the time of birth, most of the diencephalon nuclei are well developed. In the future, the size of the thalamus grows due to the growth in the size of nerve cells and the development of nerve fibers. The development of the diencephalon also consists in the complication of its interaction with other brain formations, improves the overall coordination activity. The final differentiation of the nuclei of the thalamus and hypothalamus ends at puberty.

V of the central part of the brain stem (from oblong to intermediate) is a nerve formation - a mesh creation (reticular formation). This structure has 48 nuclei and a large number of neurons that form many contacts with each other (the phenomenon of the field of sensory convergence). Through the collateral pathway, all sensitive information from the receptors of the periphery enters the reticular formation. It has been established that the mesh creation takes part in the regulation of respiration, the activity of the heart, blood vessels, digestion processes, etc. The special role of the mesh formation is in the regulation of the functional activity of the higher parts of the cerebral cortex, which ensures wakefulness (together with impulses from nonspecific structures of the thalamus). In the network formation, the interaction of afferent and efferent impulses occurs, their circulation along the ring roads of neurons, which is necessary to maintain a certain tone or degree of readiness of all body systems for changes in the state or conditions of activity. The descending pathways of the reticular formation are capable of transmitting impulses from the higher parts of the central nervous system to the spinal cord, regulating the speed of the passage of reflex acts.

telencephalon includes subcortical basal ganglia(nuclei) and two cerebral hemispheres covered by the cerebral cortex. Both hemispheres are connected by a bundle of nerve fibers that form the corpus callosum.

Among the basal nuclei, one should name the pale ball (palidum) where the centers of complex motor acts (writing, sports exercises) and facial movements are located, as well as the striatum that controls the pale ball and acts on it by slowing down. The striatum has the same effect on the cerebral cortex, causing sleep. It has also been established that the striatum takes part in the regulation of vegetative functions, such as metabolism, vascular reactions, and heat generation.

Above the brain stem in the thickness of the hemispheres there are structures that determine the emotional state, induce to action, take part in the processes of learning and memorization. These structures form the limbic system. These structures include areas of the brain such as the seahorse twirl (hippocampus), cingulate twirl, olfactory bulb, olfactory triangle, amygdala (amygdala), and anterior nuclei of the thalamus and hypothalamus. The cingulate twist, together with the seahorse twist and the olfactory bulb, form the limbic cortex, where acts of human behavior are formed under the influence of emotions. It has also been established that neurons located in the spin of the seahorse take part in the processes of learning, memory, cognition, emotions of anger and fear are immediately formed. The amygdala influences behavior and activity in meeting the needs of nutrition, sexual interest, etc. The limbic system is closely connected with the nuclei of the base of the hemispheres, as well as with the frontal and temporal lobes of the cerebral cortex. Nerve impulses that are transmitted along the descending pathways of the limbic system coordinate the autonomic and somatic reflexes of a person according to emotional state, and also carry out the connection of biologically significant signals from the external environment with the emotional reactions of the human body. The mechanism of this is that information from the external environment (from the temporal and other sensory areas of the cortex) and from the hypothalamus (about the state of the internal environment of the body) converts on the neurons of the amygdala (part of the limbic system), making synaptic connections. This forms imprints of short-term memory, which are compared with the information contained in the long-term memory and with the motivational tasks of behavior, which, finally, causes the emergence of emotions.

The cerebral cortex is represented by gray matter with a thickness of 1.3 to 4.5 mm. The area of ​​the crust reaches 2600 cm2 due to a large number furrows and whorls. There are up to 18 billion nerve cells in the cortex, which form many mutual contacts.

Under the cortex is a white matter, in which there are associative, commissural and projection pathways. Associative pathways connect individual zones (nerve centers) within one hemisphere; commissural pathways connect symmetrical nerve centers and parts (twists and furrows) of both hemispheres, passing through the corpus callosum. Projection pathways are located outside the hemispheres and connect the lower located sections of the central nervous system with the cerebral cortex. These pathways are divided into descending (from the cortex to the periphery) and ascending (from the periphery to the centers of the cortex).

The entire surface of the cortex is conditionally divided into 3 types of cortex zones (areas): sensory, motor and associative.

Sensory zones are particles of the cortex in which afferent pathways from different receptors. For example, 1 somato-sensory zone, which receives information from external receptors of all parts of the body, located in the region of the posterior-central twist of the cortex; the visual sensory zone is located on the medial surface of the occipital cortex; auditory - in the temporal lobes, etc. (for details, see subsection 4.2).

Motor zones provide efferent innervation working muscles. These zones are localized in the region of the anterocentral twist and have close connections with the sensory zones.

Associative zones are significant areas of the hemispheric cortex, which, using associative pathways, are connected with sensory and motor areas of other parts of the cortex. These zones consist mainly of polysensory neurons that are able to perceive information from different sensory areas of the cortex. Speech centers are located in these zones, they analyze all current information, and also form abstract representations, make decisions on what to perform intellectual tasks, create complex behavior programs based on previous experience and predictions for the future.

V children at the time of birth, the cerebral cortex has the same structure as in adults, however, ITS surface increases with the development of the child due to the formation of small twists and furrows, which lasts up to 14-15 years. In the first months of life, the cerebral cortex grows very rapidly, neurons mature, and intensive myelination of nerve processes takes place. Myelin performs an insulating role and promotes an increase in the speed of nerve impulses, so myelination of the sheaths of nerve processes helps to increase the accuracy and localization of the conduction of those excitations that enter the brain, or commands that go to the periphery. Myelination processes most intensively occur in the first 2 years of life. Different cortical areas of the brain in children mature unevenly, namely: sensory and motor areas complete their maturation at 3-4 years, while associative areas begin to develop intensively only from the age of 7 and this process continues up to 14-15 years. Ripens the latest frontal lobes cortex responsible for the processes of thinking, intellect and mind.

The peripheral part of the nervous system mainly innervates the separated muscles of the musculoskeletal system (with the exception of the heart muscle) and the skin, and is also responsible for the perception of external and internal information and for the formation of all acts of behavior and mental activity of a person. In contrast, the autonomic nervous system innervates all the smooth muscles of the internal organs, the muscles of the heart, blood vessels and glands. It should be remembered that this division is rather arbitrary, since the entire nervous system in the human body is not separate and whole.

Peripheral consists of spinal and cranial nerves, receptor endings of the sense organs, nerve plexuses (nodes) and ganglia. The nerve is a filamentous formation of predominantly white color in which the nerve processes (fibers) of many neurons are combined. Connective tissue and blood vessels are located between bundles of nerve fibers. If the nerve contains only fibers of afferent neurons, then it is called a sensory nerve; if the fibers are efferent neurons, then it is called the motor nerve; if it contains fibers of afferent and efferent neurons, then it is called a mixed nerve (there are most of them in the body). Nerve nodes and ganglia are located in different parts of the body of the organism (outside the CNS) and are places where one nerve process branches into many other neurons or places where one neuron switches to another in order to continue the nerve pathways. Data on the receptor endings of the sense organs, see section 4.2.

There are 31 pairs of spinal nerves: 8 pairs of cervical, 12 pairs of thoracic, 5 pairs of lumbar, 5 pairs of sacral and 1 pair of coccygeal. Each spinal nerve is formed by the anterior and posterior roots of the spinal cord, is very short (3-5 mm), occupies the gap between the intervertebral foramen and immediately outside the vertebra branches into two branches: posterior and anterior. The posterior branches of all spinal nerves metamerically (i.e., in small zones) innervate the muscles and skin of the back. The anterior branches of the spinal nerves have several ramifications (the branch branch leading to the nodes of the sympathetic division of the autonomic nervous system; the sheath branch innervates the sheath of the spinal cord itself and the main anterior branch). The anterior branches of the spinal nerves are called nerve trunks and, with the exception of the nerves of the thoracic region, they go to the nerve plexuses where they switch to second neurons sent to the muscles and skin of individual parts of the body. Allocate: cervical plexus (form 4 pairs of upper cervical spinal nerves, and from it comes the innervation of the muscles and skin of the neck, diaphragm, individual parts of the head, etc.); brachial plexus (form 4 pairs of lower cervical 1 pair of upper thoracic nerves innervating the muscles and skin of the shoulders and upper limbs); 2-11 pairs of thoracic spinal nerves innervate the respiratory intercostal muscles and the skin of the chest; lumbar plexus (form 12 pairs of thoracic and 4 pairs of upper lumbar spinal nerves innervating the lower abdomen, thigh muscles and gluteal muscles); sacral plexus (form 4-5 pairs of sacral and 3 upper pairs of coccygeal spinal nerves that innervate the pelvic organs, muscles and skin of the lower limb; among the nerves of this plexus, the sciatic nerve is the largest in the body); shameful plexus (form 3-5 pairs of coccygeal spinal nerves that innervate the genitals, muscles of the small and large pelvis).

There are twelve pairs of cranial nerves, as mentioned earlier, and they are divided into three groups: sensory, motor and mixed. The sensory nerves include: I pair - olfactory nerve, II pair - optic nerve, VJIJ pair - cochlear nerve.

Motor nerves include: IV paratrochlear nerve, VI pair - abducens nerve, XI pair - accessory nerve, XII pair - hypoglossal nerve.

Mixed nerves include: III para-oculomotor nerve, V pair - trigeminal nerve, VII pair - facial nerve, IX pair - glossopharyngeal nerve, X pair - vagus nerve. The peripheral nervous system in children usually develops at the age of 14-16 (in parallel with the development of the central nervous system) and this consists in an increase in the length of nerve fibers and their myelination, as well as in the complication of interneuronal connections.

The vegetative (autonomous) nervous system (ANS) of a person regulates the functioning of internal organs, metabolism, adapts the level of the body's work to the current needs of existence. This system has two divisions: sympathetic and parasympathetic, which have parallel nerve paths to all organs and vessels of the body and often act on their work with the opposite effect. Sympathetic innervations habitually accelerate functional processes (increase the frequency and strength of heart contractions, expand the lumen of the bronchi of the lungs and all blood vessels, etc.), and parasympathetic innervations slow down (lower) the course of functional processes. An exception is the action of the ANS on the smooth muscles of the stomach and intestines and on the processes of urination: here, sympathetic innervations inhibit muscle contraction and urine formation, while parasympathetic ones, on the contrary, accelerate it. In some cases, both departments can reinforce each other in their regulatory effect on the body (for example, when physical activity both systems can increase the work of the heart). In the first periods of life (up to 7 years), the child exceeds the activity of the sympathetic part of the ANS, which causes respiratory and cardiac arrhythmias, excessive sweating and others. The predominance of sympathetic regulation in childhood is due to the peculiarities child's body, develops and requires increased activity of all vital processes. The final development of the autonomic nervous system and the establishment of a balance in the activity of both departments of this system is completed at the age of 15-16. The centers of the sympathetic division of the ANS are located on both sides along the spinal cord at the level of the cervical, thoracic and lumbar regions. The parasympathetic division has centers in the medulla oblongata, midbrain and diencephalon, as well as in the sacral spinal cord. The highest center of autonomic regulation is located in the region of the hypothalamus of the diencephalon.

The peripheral part of the ANS is represented by nerves and nerve plexuses (nodes). The nerves of the autonomic nervous system are usually gray in color, since the processes of the neurons that form do not have a myelin sheath. Very often, the fibers of the neurons of the autonomic nervous system are included in the composition of the nerves of the somatic nervous system, forming mixed nerves.

The axons of the neurons of the central part of the sympathetic division of the ANS are first included in the roots of the spinal cord, and then, as a branch, go to the prevertebral nodes of the peripheral division, located in chains on both sides of the spinal cord. These are the so-called pre-bundles of the fiber. In the nodes, excitation switches to other neurons and goes after the nodal fibers to the working organs. A number of nodes of the sympathetic division of the ANS form the left and right sympathetic trunks along the spinal cord. Each trunk has three cervical sympathetic nodes, 10-12 thoracic, 5 lumbar, 4 sacral and 1 coccygeal. In the coccygeal region, both trunks are connected to each other. Paired cervical nodes are divided into upper (largest), middle and lower. From each of these nodes, cardiac branches branch off, reaching the cardiac plexus. From the cervical nodes there are also branches to the blood vessels of the head, neck, chest and upper limbs, forming around them the choroid plexuses. Along the vessels, the sympathetic nerves reach the organs (the salivary glands, pharynx, larynx, and pupils of the eyes). Lower cervical knot often combined with the first thoracic, resulting in a large cervicothoracic node. cervical sympathetic nodes associated with the cervical spinal nerves, which form the cervical and brachial plexus.

Two nerves depart from the nodes of the thoracic region: a large gastrointestinal (from 6-9 nodes) and a small gastrointestinal (from 10-11 nodes). Both nerves pass through the diaphragm into the abdominal cavity and end in the abdominal (solar) plexus, from which numerous nerves branch off to the abdominal organs. The right vagus nerve connects to the abdominal plexus. Branches also depart from the thoracic nodes to the organs of the posterior mediastinum, aortic, cardiac and pulmonary plexuses.

From the sacral section of the sympathetic trunk, which consists of 4 pairs of nodes, fibers depart to the crisis and coccygeal spinal nerves. In the pelvic area is the hypogastric plexus of the sympathetic trunk, from which the nerve fibers depart to the organs of the small pelvis *

The parasympathetic part of the autonomic nervous system is made up of neurons. located in the nuclei of the oculomotor, facial, glossopharyngeal and vagus nerves of the brain, as well as from nerve cells located in the II-IV sacral segments of the spinal cord. In the peripheral part of the parasympathetic part of the autonomic nervous system, the nerve ganglions are not very clearly defined, and therefore the innervation is mainly carried out due to the long processes of the central neurons. The schemes of parasympathetic innervation are mostly parallel to the same schemes from the sympathetic department, but there are some peculiarities. For example, parasympathetic innervation of the heart is carried out by a branch of the vagus nerve through the sinoatrial node (pacemaker) of the conduction system of the heart, and sympathetic innervation is carried out by many nerves coming from the thoracic nodes of the sympathetic division of the autonomic nervous system and go directly to the muscles of rage and ventricles of the heart.

The most important parasympathetic nerves are the right and left vagus nerves, numerous fibers of which innervate the organs of the neck, chest, and abdomen. In many cases branches vagus nerves form plexuses with sympathetic nerves (cardiac, pulmonary, abdominal and other plexuses). As part of the third pair of cranial nerves (oculomotor), there are parasympathetic fibers that go to the smooth muscles of the eyeball and, when excited, cause pupil constriction, while excitation of sympathetic fibers dilates the pupil. As part of the VII pair of cranial nerves (facial), parasympathetic fibers innervate the salivary glands (reduce saliva secretion). The fibers of the sacral part of the parasympathetic nervous system take part in the formation of the hypogastric plexus, from which branches go to the organs of the small pelvis, thereby regulating the processes of urination, defecation, sexual administration, etc.