The spinal cord is part of the central nervous system and has a direct connection with the internal organs, skin and muscles of a person. In appearance, the spinal cord resembles a cord that takes place in the spinal canal. Its length is about half a meter, and the width usually does not exceed 10 millimeters.

The spinal cord is divided into two parts - right and left. On top of it there are three shells: hard, soft (vascular) and arachnoid. Between the last two is a space filled with cerebrospinal fluid. In the central region of the spinal cord, gray matter can be found, on a horizontal section similar in appearance to a "moth". The gray matter is formed from the bodies of nerve cells (neurons), the total number of which reaches 13 million. Cells similar in structure and having the same functions create gray matter nuclei. There are three types of protrusions (horns) in the gray matter, which are divided into the anterior, posterior and lateral horn of the gray matter. The anterior horns are characterized by the presence of large motor neurons, the posterior horns are formed by small intercalary neurons, and the lateral horns are the location of the visceral motor and sensory centers.

The white matter of the spinal cord surrounds the gray matter on all sides, forming a layer created by myelinated nerve fibers stretching in an ascending and descending direction. Bundles of nerve fibers formed by a combination of processes of nerve cells form pathways. There are three types of conducting bundles of the spinal cord: short, which set the connection of brain segments at different levels, ascending (sensory) and descending (motor). 31-33 pairs of nerves are involved in the formation of the spinal cord, divided into separate sections called segments. The number of segments is always the same as the number of pairs of nerves. The function of the segments is to innervate specific areas of the human body.

Spinal Cord Functions

The spinal cord is endowed with two important functions - reflex and conduction. The presence of the simplest motor reflexes (withdrawal of the hand in case of a burn, extension of the knee joint when hitting the tendon with a hammer, etc.) is due to the reflex function of the spinal cord. The connection between the spinal cord and skeletal muscles is possible due to reflex arc, which is the path of passage of nerve impulses. The conduction function consists in the transmission of nerve impulses from the spinal cord to the brain using ascending paths of movement, as well as from the brain along descending paths to organs. various systems organism.

The brain is the control center of our body. All feelings, thoughts or actions are due to the work of the central nervous system. The brain controls the body by sending electrical signals along the nerve fibers, which first combine into the spinal cord and then diverge to various organs (the peripheral nervous system). The spinal cord is a "cord" of nerve fibers and is located in the middle of the spinal column. The brain and spinal cord together form central nervous system (CNS).

The brain and spinal cord are washed clear liquid, called spinal, or, for short, liquor.

The CNS is made up of billions of nerve cells called neurons. There are also so-called glial cells to support the neurons. Sometimes glial cells can become malignant, becoming the cause of the onset. Various areas brain control various bodies bodies, as well as our thoughts, memories and feelings. There is, for example, a speech center, a vision center, and so on.

Tumors of the central nervous system can develop in any area of ​​the brain, arising from:

• Cells that directly make up the brain;
• Nerve cells entering or exiting;
• Meninges.

Metastases are rare in children.

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The human spinal cord is the most important organ of the central nervous system, which communicates all organs with the central nervous system and conducts reflexes. It is covered on top with three shells:

• solid, cobweb and soft

Between the arachnoid and soft (vascular) membrane and in its central canal is located cerebrospinal fluid (liquor)

V epidural space (gap between solid meninges and the surface of the spine) - vessels and adipose tissue

What is the external structure of the spinal cord?

This is a long cord in the spinal canal, in the form of a cylindrical cord, about 45 mm long, about 1 cm wide, flatter in front and behind than on the sides. It has conditional upper and lower bounds. The upper one starts between the line of the foramen magnum and the first cervical vertebra: at this point, the spinal cord connects to the brain through the intermediate oblongata. The lower one is at the level of 1-2 lumbar vertebrae, after which the cord takes on a conical shape and then “degenerates” into a thin spinal cord ( terminal) with a diameter of about 1 mm, which stretches to the second vertebra of the coccygeal region. The terminal thread consists of two parts - inner and outer:

• inner - about 15 cm long, consists of nervous tissue, intertwined with lumbar and sacral nerves and located in the sac of the dura mater
• external - about 8 cm, starts below the 2nd vertebra sacral department and stretches in the form of a combination of solid, cobweb and soft shells up to the 2nd coccygeal vertebra and fuses with the periosteum

The outer, hanging down to the coccyx terminal thread with nerve fibers intertwining it is very similar in appearance to a ponytail. Therefore, pain and phenomena that occur when the nerves are pinched below the 2nd sacral vertebra are often called cauda equina syndrome.

The spinal cord has thickenings in the cervical and lumbosacral regions. This finds its explanation in the presence a large number outgoing nerves in these places, going to the upper, as well as to the lower extremities:

1. Cervical thickening extends from the 3rd - 4th cervical vertebrae to the 2nd thoracic, reaching a maximum in the 5th - 6th
2. Lumbosacral - from the level of the 9th - 10th thoracic vertebrae to the 1st lumbar with a maximum in the 12th thoracic

Gray and white matter of the spinal cord

If we consider the structure of the spinal cord in cross section, then in the center of it you can see a gray area in the form of a butterfly opening its wings. This is the gray matter of the spinal cord. It is surrounded on the outside by white matter. Cell structure gray and white matter is different from each other, as are their functions.

The gray matter of the spinal cord is composed of motor and interneurons.:

• motor neurons transmit motor reflexes
• intercalary - provide a connection between the neurons themselves

White matter is made up of so-called axons- nerve processes from which the fibers of the descending and ascending pathways are created.

Butterfly wings are narrower anterior horns gray matter, wider - rear. In the anterior horns are motor neurons, in the rear intercalary. Between the symmetrical side parts there is a transverse bridge made of brain tissue, in the center of which there is a channel that communicates top with the ventricle of the brain and filled with cerebrospinal fluid. In some departments or even along the entire length in adults, the central canal may become overgrown.

Relative to this canal, to the left and to the right of it, the gray matter of the spinal cord looks like columns of a symmetrical shape, interconnected by anterior and posterior commissures:

• the anterior and posterior pillars correspond to the anterior and posterior horns in cross section
• side protrusions form a side pillar

Lateral protrusions are not present throughout their entire length, but only between the 8th cervical and 2nd lumbar segments. Therefore, the cross section in segments where there are no lateral protrusions has an oval or round shape.

The connection of symmetrical pillars in the front and back parts forms two furrows on the surface of the brain: anterior, deeper, and posterior. The anterior fissure ends with a septum adjoining the posterior border of the gray matter.

Spinal nerves and segments

To the left and right of these central furrows are located respectively anterolateral and posterolateral furrows through which the anterior and posterior filaments exit ( axons) that form the nerve roots. The anterior spine in its structure is motor neurons anterior horn. Rear, responsible for sensitivity, consists of intercalary neurons back horn. Immediately at the exit of the brain segment, both the anterior and posterior roots unite into one nerve or ganglion (ganglion). Since there are two anterior and two posterior roots in each segment, in total they form two spinal nerve (one on each side). Now it is easy to calculate how many nerves the human spinal cord has.

To do this, consider its segmental structure. There are 31 segments in total:

• 8 - in the cervical region
• 12 - in the chest
• 5 - lumbar
• 5 - in the sacral
• 1 - in the coccygeal

This means that the spinal cord has a total of 62 nerves - 31 on each side.

The sections and segments of the spinal cord and the spine are not at the same level, due to the difference in length (the spinal cord is shorter than the spine). This must be taken into account when comparing the brain segment and the number of the vertebra during radiology and tomography: if at the beginning of the cervical region this level corresponds to the number of the vertebra, and in its lower part it lies one vertebra higher, then in the sacral and coccygeal regions this difference is already several vertebrae.

Two Important Functions of the Spinal Cord

The spinal cord performs two important functions − reflex and conductive. Each of its segments is associated with specific organs, ensuring their functionality. For instance:

• Cervical and thoracic - communicates with the head, hands, organs chest, chest muscles
• Lumbar - organs of the gastrointestinal tract, kidneys, muscular system torso
• Sacral region - pelvic organs, legs

Reflex functions are simple reflexes laid down by nature. For instance:

• pain reaction - pull your hand away if it hurts.
• knee jerk

Reflexes can be carried out without the participation of the brain

This is proven by simple experiments on animals. Biologists conducted experiments with frogs, testing how they react to pain in the absence of a head: a reaction was noted to both weak and strong pain stimuli.

The conduction functions of the spinal cord consist in conducting an impulse along the ascending path to the brain, and from there - along the descending path in the form of a return command to some organ

Thanks to this conductive connection, any mental action is carried out:
get up, go, take, throw, pick up, run, cut off, draw- and many others that a person, without noticing, commits in his Everyday life at home and at work.

Such a unique connection between the central brain, spinal cord, the entire CNS and all organs of the body and its limbs, as before, remains a dream of robotics. Not a single, even the most modern robot is yet able to carry out even a thousandth of those various movements and actions that are subject to a bioorganism. As a rule, such robots are programmed for highly specialized activities and are mainly used in conveyor automatic production.

Functions of gray and white matter. To understand how these magnificent functions of the spinal cord are carried out, consider the structure of the gray and white matter of the brain at the cellular level.

The gray matter of the spinal cord in the anterior horns contains nerve cells large sizes, which are called efferent(motor) and are combined into five nuclei:

• central
• anterolateral
• posterolateral
• anteromedial and posterior medial

Sensitive roots of small cells back horns are specific cellular processes from sensitive nodes of the spinal cord. V posterior horns the structure of the gray matter is heterogeneous. Most of the cells form their own nuclei (central and thoracic). The border zone of the white matter, located near the posterior horns, is adjoined by the spongy and gelatinous zones of the gray matter, the processes of the cells of which, together with the processes of small diffusely scattered cells of the posterior horns, form synapses (contacts) with the neurons of the anterior horns and between adjacent segments. These neurites are called anterior, lateral, and posterior proper bundles. Their connection with the brain is carried out with the help of white matter pathways. Along the edge of the horns, these bundles form a white border.

The lateral horns of the gray matter perform the following important functions:

• In the intermediate zone of gray matter (lateral horns) are sympathetic cells vegetative nervous system, it is through them that communication with internal organs is carried out. The processes of these cells are connected to the anterior roots
• Here is formed spinocerebellar path:
  At the level of the cervical and upper thoracic segments is reticular zone - a bundle of a large number of nerves associated with zones of activation of the cerebral cortex and reflex activity.

The segmental activity of the gray matter of the brain, the posterior and anterior roots of the nerves, the own bundles of white matter, bordering the gray, is called the reflex function of the spinal cord. The reflexes themselves are called unconditional, according to the definition of Academician Pavlov.

The conductive functions of the white matter are carried out by means of three cords - its outer sections, limited by furrows:

• Anterior funiculus - the area between the anterior median and lateral grooves
• Posterior funiculus - between the posterior median and lateral grooves
• Lateral funiculus - between the anterolateral and posterolateral grooves

White matter axons form three conduction systems:

• short bundles called associative fibers that connect different segments of the spinal cord
• ascending sensitive (afferent) bundles directed to the parts of the brain
• descending motor (efferent) beams directed from the brain to the neurons of the gray matter of the anterior horns

Ascending and descending conduction pathways. Consider, for example, some functions of the paths of the cords of the white matter:

Anterior cords:

• Anterior pyramidal (cortical-spinal) tract- transmission of motor impulses from the cerebral cortex to the spinal cord (anterior horns)
• Spinothalamic anterior pathway- transmission of impulses of touch impact on the surface of the skin (tactile sensitivity)
• Covering-spinal tract-connecting the visual centers under the cerebral cortex with the nuclei of the anterior horns, creates defensive reflex caused by auditory or visual stimuli
• Bundle of Geld and Leventhal (pre-door-spinal path)- fibers of the white matter connect the vestibular nuclei of eight pairs of cranial nerves with the motor neurons of the anterior horns
• Longitudinal posterior beam - connecting the upper segments of the spinal cord with the brain stem, coordinates the work eye muscles with neck, etc.

The ascending paths of the lateral cords conduct impulses of deep sensitivity (sensation of one's body) along the cortical-spinal, spinothalamic and tectospinal tracts.

Descending tracts of the lateral cords:

• Lateral corticospinal (pyramidal)- transmits the impulse of movement from the cerebral cortex to the gray matter of the anterior horns
• Red nuclear-spinal tract(located in front of the lateral pyramidal), the spinal cerebellar posterior and spinothalamic lateral pathways adjoin to it on the side.
  The red nuclear-spinal path carries out automatic control of movements and muscle tone at a subconscious level.

V different departments spinal cord different ratio of gray and white medulla. This is due to the different number of ascending and descending paths. There is more gray matter in the lower spinal segments. As you move up, it becomes less, and the white matter, on the contrary, is added, as new ascending paths are added, and at the level of the upper cervical segments and the middle part of the chest white - most of all. But in the area of ​​​​both cervical and lumbar thickenings, gray matter predominates.

As you can see, the spinal cord has a very complex structure. The connection of nerve bundles and fibers is vulnerable, and serious injury or a disease can disrupt this structure and lead to disruption of the conduction pathways, due to which there may be complete paralysis and loss of sensitivity below the “break” point of conduction. Therefore, at the slightest dangerous signs, the spinal cord must be examined and treated in time.

Puncture of the spinal cord

For the diagnosis of infectious diseases (encephalitis, meningitis, and other diseases), a puncture of the spinal cord is used ( lumbar puncture) - leading the needle into the spinal canal. It is carried out in this way:
V subarachnoid the space of the spinal cord at a level below the second lumbar vertebra, a needle is inserted and a fence is taken cerebrospinal fluid (liquor).
This procedure is safe, since the spinal cord is absent below the second vertebra in an adult, and therefore there is no threat of damage to it.

However, it requires special care not to bring infection or epithelial cells under the membrane of the spinal cord.

Spinal cord puncture is performed not only for diagnosis, but also for treatment, in such cases:

• injection of chemotherapy drugs or antibiotics under the lining of the brain
• for epidural anesthesia during operations
• for the treatment of hydrocephalus and reduction intracranial pressure(removal of excess liquor)

Spinal puncture has the following contraindications:

• spinal stenosis
• displacement (dislocation) of the brain
• dehydration (dehydration)

Take care of this important organ, do elementary prevention:

1. Take Antivirals During a Viral Meningitis Epidemic
2. Try not to have picnics in the forested area in May-early June (the period of activity of the encephalitis tick)

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The brain is divided into three sections: posterior, middle and anterior.

The medulla oblongata, pons, and cerebellum belong to the posterior, and the diencephalon and cerebral hemispheres to the anterior. All departments, including the cerebral hemispheres, form the brain stem. Inside the cerebral hemispheres and in the brain stem there are cavities filled with fluid.

Functions of the brain regions:

Oblong - is a continuation of the spinal cord, contains nuclei that control vegetative functions body (breathing, heart function, digestion).

The bridge is a continuation of the medulla oblongata; nerve bundles pass through it, connecting the anterior and midbrain with oblong and dorsal. In its substance lie the nuclei of the cranial nerves (trigeminal, facial, auditory).

The cerebellum is located in the back of the head behind the medulla oblongata and the bridge, is responsible for the coordination of movements, maintaining posture, body balance.

The midbrain connects the anterior and posterior, contains the nuclei of orienting reflexes to visual and auditory stimuli, controls muscle tone. It contains pathways between other parts of the brain.

The diencephalon receives impulses from all receptors, participates in the occurrence of sensations. Its parts work together internal organs and regulate vegetative functions: metabolism, body temperature, blood pressure, breath. The diencephalon consists of the thalamus and hypothalamus.

The cerebral hemispheres are the most developed and largest part of the brain. Centers of speech, memory, thinking, hearing, vision, musculoskeletal sensitivity, taste and smell, movement. Each hemisphere is divided into four lobes: frontal, parietal, temporal and occipital.

The cells of the cortex perform various functions and therefore three types of zones can be distinguished in the cortex:

Sensory zones (receive impulses from receptors).

Associative zones (process and store the information received, as well as develop a response based on past experience).

Motor zones (send signals to organs).

The spinal cord is a part of the central nervous system. It is a long 45 cm cord with a diameter of 1 cm. It is located in the spinal canal. There are two furrows in front and behind, dividing it into left and right half. It is covered with three shells: hard, arachnoid and vascular. The space between the arachnoid and choroid covered with cerebrospinal fluid.

In the center of the spinal cord passes the spinal canal, consisting of intercalary and motor neurons, and the outer one is formed by the white matter of axons. In the gray matter, the anterior horns, in which the motor neurons are located, and the posterior, in which the intercalary neurons are located, are distinguished.

There are 31 segments in the spinal cord. From segments of the cervical and upper chest parts spinal cord nerves depart to the muscles of the head, upper limbs, organs chest cavity, to the heart and lungs. Segments of the thoracic and lumbar parts control the muscles of the trunk and organs abdominal cavity, and the lower lumbar and sacral muscles - with muscles lower extremities and lower abdomen.

The spinal cord performs two functions: reflex and conduction.

Reflex - provides the implementation of the simplest reflexes (flexion and extension of the limbs, withdrawal of the hand, knee jerk).

Conduction - nerve impulses from receptors along the ascending paths of the spinal cord go to the brain, and along the descending paths there are commands to the working organs from the brain.

Simple motor reflexes are carried out under the control of one spinal cord. All complex movements - from walking to performing any labor processes - require the mandatory participation of the brain.

Spinal cord. The spinal cord is a long cord. It fills the cavity of the spinal canal and has a segmental structure corresponding to the structure of the spine. In the center of the spinal cord is gray matter - a cluster of nerve cells surrounded by white matter formed by nerve fibers (Fig. 7).

In the spinal cord are the reflex centers of the muscles of the trunk, limbs and neck. With their participation, tendon reflexes are carried out in the form of a sharp muscle contraction (knee, Achilles reflexes), stretch reflexes, flexion reflexes, various reflexes aimed at maintaining a certain posture. Reflexes of urination and defecation, reflex swelling of the penis and ejaculation in men (erection and ejaculation) are associated with the function of the spinal cord. The spinal cord also performs a conductive function. The nerve fibers that make up the bulk of the white matter form the pathways of the spinal cord. Through these pathways, communication is established between various parts of the central nervous system and impulses pass in the ascending and descending directions. Through these pathways, information enters the overlying parts of the brain, from which impulses depart that change activity. skeletal muscles and internal organs. The activity of the spinal cord in humans is largely subordinated to the coordinating influences of the overlying parts of the central nervous system. Ensuring the implementation of vital important functions The spinal cord develops earlier than other parts of the nervous system. When the embryo's brain is at the stage of cerebral vesicles, the spinal cord already reaches a considerable size. In the early stages of fetal development, the spinal cord fills the entire cavity of the spinal canal. Then spinal column overtakes the spinal cord in growth, and by the time of birth it ends at the level of the third lumbar vertebra. In newborns, the length of the spinal cord is 14-16 cm, by the age of 10 it doubles. The spinal cord grows slowly in thickness. On a cross section of the spinal cord of children early age there is a predominance of the anterior horns over the posterior ones. An increase in the size of nerve cells in the spinal cord is observed in children during their school years.

Brain. The spinal cord passes directly into the brainstem located in the skull (Fig. 8).

A direct continuation of the spinal cord is the medulla oblongata, which together with the bridge of the brain (pons varolii) forms back brain. its nerve cells form nerve centers that regulate reflex functions sucking, swallowing, digestion, cardiovascular and respiratory systems, as well as nuclei V-XII pairs cranial nerves and parasympathetic nerve fibers running in their composition. The need to implement the listed vital functions from the moment of birth of a child determines the degree of maturity of the structures of the medulla oblongata already in the neonatal period. By the age of 7, the maturation of the nuclei of the medulla oblongata is basically over. At the level of the medulla, the reticular formation begins, consisting of a network of nerve cells with which the afferent and efferent pathways are in contact. The axons of various neurons form multiple collaterals, in contact with huge number reticular cells. One axon can interact with 27,500 neurons. The reticular formation extends to the level of the midbrain and diencephalon. In the reticular formation, a descending system is distinguished, which regulates, under the influence of influence from the higher parts of the central nervous system, the reflex activity of the spinal cord and muscle tone. It includes the anterior part of the medulla oblongata and the middle part of the pons. The ascending system - the structures of the brainstem, midbrain and diencephalon - receives impulses from the spinal cord and sensory systems, has a general non-specific effect on the overlying parts of the brain. She, as will be shown later, plays an important role in the regulation of the level of wakefulness and organization behavioral responses. Part midbrain are included legs of the brain and brain roof. Here are clusters of nerve cells in the form of the upper and lower tubercles of the quadrigemina, the red nucleus, the substantia nigra, the nuclei of the oculomotor and trochlear nerves, and the reticular formation. In the upper and lower tubercles quadrigemina the simplest visual and auditory reflexes are closed and their interaction is carried out (movement of the ears, eyes, turn towards the stimulus). black substance participates in the complex coordination of finger movements, acts of swallowing and chewing. red core is directly related to the regulation of muscle tone. Behind the medulla oblongata and the pons is located cerebellum. The cerebellum is an organ that regulates and coordinates motor functions and their vegetative support. Information from various muscular, vestibular, auditory and visual receptors, signaling the position of the body in space and the nature of the execution of movements, is integrated in the cerebellum with influences from the overlying parts of the brain, which ensures the implementation of a smooth coordinated motor act based on the feedback principle. Removal of the cerebellum does not entail the loss of the ability to move, but it disrupts the nature of the actions performed. Enhanced growth of the cerebellum is noted in the first year of a child's life, which is determined by the formation of differentiated and coordinated movements during this period. In the future, the pace of its development is reduced. By the age of 15, the cerebellum reaches the size of an adult.

The most important functions are performed by structures diencephalon, which includes the visual tubercle (thalamus) and hypothalamic region (hypothalamus). Hypothalamus, despite its small size, it contains dozens of highly differentiated nuclei. The hypothalamus is associated with the autonomic functions of the body and carries out the coordination and integrative activity of the sympathetic and parasympathetic divisions. The paths from the hypothalamus go to the middle, medulla oblongata and spinal cord, ending in neurons - sources of preganglionic fibers. The vegetative effects of the hypothalamus, its different departments have different directions and biological significance. The posterior sections lead to the appearance of sympathetic-type effects, the anterior - parasympathetic. The ascending influences of these departments are also multidirectional: the posterior ones have an excitatory effect on the cerebral cortex, while the anterior ones have an inhibitory effect. connection of the hypothalamus with one of the the most important glands internal secretion - the pituitary gland - provides nervous regulation of endocrine function. In the cells of the nuclei of the anterior hypothalamus, neurosecretion is produced, which is transported along the fibers of the hypothalamic-pituitary pathway to the neurohypophysis. This is facilitated by an abundant blood supply, and vascular connections hypothalamus and pituitary gland. The hypothalamus and pituitary gland are often combined into hypothalamic-pituitary system playing essential role in the regulation of endocrine glands. One of the major nuclei of the hypothalamus gray mound - takes part in the regulation of the functions of many endocrine glands and metabolism. The destruction of the gray tubercle causes atrophy of the gonads. Its prolonged irritation can lead to early puberty, skin ulcers, gastric and duodenal ulcers.

The hypothalamus is involved in the regulation of body temperature. Its role in the regulation of water metabolism and carbohydrate metabolism has been proven. The nuclei of the hypothalamus are involved in many complex behavioral reactions (sexual, food, aggressive-defensive). The hypothalamus plays an important role in the formation of basic biological motivations (hunger, thirst, sex drive) and emotions of positive and negative sign. The variety of functions carried out by the structures of the hypothalamus gives grounds to regard it as the highest subcortical center for the regulation of vitality. important processes, their integration into complex systems providing appropriate adaptive behavior.

The differentiation of the nuclei of the hypothalamus by the time of birth is not completed and proceeds unevenly in ontogenesis. The development of the nuclei of the hypothalamus ends at puberty. thalamus(visual tubercle) is a significant part of the diencephalon. This is a multinuclear formation, connected by bilateral connections with the cerebral cortex. It consists of three groups of nuclei. Relay nuclei transmit visual, auditory, skin-muscular-articular information to the corresponding projection areas of the cerebral cortex. Associative nuclei transmit it to the associative sections of the cerebral cortex. Nonspecific nuclei (continuation of the reticular formation of the midbrain) have an activating effect on the cerebral cortex.

Centripetal impulses from all body receptors (with the exception of olfactory ones), before reaching the cerebral cortex, enter the nuclei of the thalamus. Here the received information is processed, gets emotional coloring and goes to the cerebral cortex. By the time of birth, most of the nuclei of the visual hillocks are well developed. After birth, the size of the visual tubercles increase due to the growth of nerve cells and the development of nerve fibers. The ontogenetic direction of the development of the structures of the diencephalon consists in increasing their interconnections with other brain formations, which creates conditions for improving the coordination activity of its various departments and the diencephalon as a whole. In the development of the diencephalon, an essential role belongs to the descending influences of the cortical fields of the telencephalon.

Finite, or anterior, brain, includes the basal ganglia and the cerebral hemispheres. The main part of the telencephalon, which reaches the greatest development in humans, are the cerebral hemispheres.

Large hemispheres of the brain located above the anterior dorsal surface of the brainstem. They are connected by large bundles of nerve fibers that form corpus callosum. In an adult, the mass of the cerebral hemispheres is about 80% of the mass of the brain and 40 times the mass of the trunk. Structural and functional organization of the cerebral cortex. The cerebral cortex is thin layer gray matter on the surface of the hemispheres. In the process of evolution, the surface of the cortex intensively increased in size due to the appearance of furrows and convolutions. The total surface area of ​​the cortex in an adult reaches 2200-2600 cm 2. The thickness of the cortex in various parts hemispheres ranges from 1.3 to 4.5 mm. There are 12 to 18 billion nerve cells in the cortex. The processes of these cells form a huge number of contacts, which creates conditions for the most complex processes processing and storage of information.

On the bottom and inner surface hemispheres are located old and ancient bark, or archi- and paleocortex. Functionally, these sections of the cerebral cortex are closely related to the hypothalamus, amygdala, and some midbrain nuclei. All these structures are limbic system of the brain. As will be shown later, the limbic system plays a critical role in shaping emotions and attention. The highest centers of vegetative regulation are also located in the old and ancient bark. On the outer surface of the hemispheres, the phylogenetically newest cortex is located, appearing only in mammals and reaching the greatest development in humans. This neocortex.

The cerebral cortex has 6--7 layers, differing in shape, size and location of neurons (Fig. 9). Between the nerve cells of all layers of the cortex, in the course of their activity, both permanent and temporary connections arise.

According to the peculiarities of the cellular composition and structure, the cerebral cortex is divided into a number of sections. They are called cortical fields.

Under the cortex is the white matter of the cerebral hemispheres. Associative, commissural and projection fibers are distinguished in the white matter. association fibers interconnect separate parts of the same hemisphere. Short associative fibers connect individual convolutions and close fields. Long fibers - convolutions of various lobes within one hemisphere. Commissural fibers connect symmetrical parts of both hemispheres. Most of them pass through the corpus callosum. Projection fibers go beyond the hemispheres. They are part of the descending and ascending pathways, along which the two-way connection of the cortex with the underlying parts of the central nervous system is carried out. There are known cases of the birth of children deprived of the cerebral cortex. This anencephaly. They usually only live for a few days. But there is a known case of the life of an anencephalus for 3 years 9 months. After his death, an autopsy revealed that the cerebral hemispheres were completely absent, and two bubbles were found in their place. During the first year of life, this child slept almost all the time. He did not respond to sound or light. Having lived for almost 4 years, he did not learn to speak, walk, recognize his mother, although he had (some) congenital reactions: he sucked when a nipple of the mother’s breast or a nipple was put into his mouth, swallowed, etc.

Observations on animals with remote hemispheres of the brain and on anencephaly show that in the process of phylogenesis the importance of the higher parts of the CNS in the life of the organism sharply increases. going on function corticolization, subordination of complex reactions of the body to the cerebral cortex. Everything that is acquired by the body during an individual life is associated with the function of the cerebral hemispheres. Higher nervous activity is associated with the function of the cerebral cortex. The body's interaction with external environment, his behavior in the surrounding material world are connected with the large hemispheres of the brain. Together with the nearest subcortical centers, the brain stem and spinal cord, the cerebral hemispheres unite the individual parts of the body into a single whole, carry out the nervous regulation of the functions of all organs. In experiments with the removal of various parts of the cortex, their irritation and during registration electrical activity In the brain, the presence of three types of cortical regions was established: sensory, motor, and associative (Fig. 10).

Sensory areas of the cerebral cortex. Afferent fibers carrying signals from various receptors come to certain areas of the cortex. Each receptor apparatus corresponds to a certain area in the cortex. I.P. Pavlov called these areas the cortical nucleus of the analyzer. In the sensory zones, primary and secondary projection fields are distinguished. The neurons of the projection primary fields highlight individual signs of the signal. In the field of visual projection, for example, the place of an object in the field of view, the direction of movement, contour, color, and contrast are analyzed. The destruction of this area leads to the loss of the ability to primary analysis of external stimuli in a certain part of the visual field. With irritation of the primary visual zone during operations, the appearance of light flickers, color spots is noted; when the projection field of the auditory cortex is irritated, the patient hears tones, individual sounds.

With limited damage to secondary, for example visual, fields, the patient clearly sees individual elements images, but cannot combine them into a coherent image, recognize a familiar object (visual agnosia). Irritation of secondary sensory zones in a person during an operation causes formalized visual and complex objects. auditory hallucinations: sounds of music, speech, etc.

Sensory zones are localized in certain areas of the cortex: the visual sensory zone is located in occipital region both hemispheres, auditory - in the temporal region, zone taste sensations- in the lower part of the parietal regions, the somatosensory zone, which analyzes impulses from the receptors of muscles, joints, tendons, and skin, is located in the region of the posterior central gyrus (see Fig. 10).

motor areas of the cortex. Zones, the irritation of which naturally causes a motor reaction, is called motor or motor. They are located in the region of the anterior central gyrus. The motor cortex has bilateral intracortical connections with all sensory areas. This ensures close interaction of sensory and motor zones.

association areas of the cortex. The human cerebral cortex "is characterized by the presence of a vast area that does not have direct afferent and efferent connections with the periphery. These areas, connected by an extensive system of connections of associative fibers with sensory and motor zones, are called associative or tertiary cortical zones. V back departments in the cortex they are located between the parietal, occipital and temporal regions, in the anterior sections they occupy the main surface of the frontal lobes. The associative cortex is either absent or poorly developed in all mammals up to primates. In humans, the posterior associative cortex occupies about half, and the frontal regions 25% of the entire surface of the cortex. In terms of structure, they are distinguished by a particularly powerful development of the upper associative layers of cells in comparison with the system of afferent and efferent neurons. Their feature is also the presence of polysensory neurons - cells that perceive information from various sensory systems.

The association cortex also contains centers associated with speech activity. Associative areas of the cortex are considered as structures responsible for the synthesis of incoming information, and as an apparatus necessary for the transition from visual perception to abstract symbolic processes. The formation of a second signaling system peculiar only to humans is associated with the associative zones of the cortex.

Clinical observations show that with the defeat of the posterior associative areas, complex forms of orientation in spaces, constructive activity are violated, it is difficult to perform all intellectual operations that are carried out with the participation of spatial analysis (counting, perception of complex semantic images). With the defeat of speech zones, the ability to perceive and reproduce speech is impaired. Damage to the frontal areas of the cortex leads to the impossibility of implementing complex behavioral programs that require the selection of significant signals based on past experience and foreseeing the future.

Development of the cerebral cortex how a phylogenetically new formation occurs during long period ontogeny. By the time a child is born, the cerebral cortex has the same type of structure as in an adult. However, its surface after birth increases significantly due to the formation of small furrows and convolutions. During the first months of life, the development of the cortex proceeds at a very rapid pace. Most neurons acquire a mature form, myelination of nerve fibers occurs. Different cortical zones mature unevenly. The somatosensory and motor cortex matures the earliest, while the visual and auditory cortex matures somewhat later. The maturation of the projection (sensory and motor) zones is generally completed by the age of 3 years. The associative cortex matures much later. By the age of 7, there is a significant leap in the development of associative areas.

However, their structural maturation - the differentiation of nerve cells, the formation of neural ensembles and connections of the associative cortex with other parts of the brain - occurs up to adolescence. The frontal areas of the cortex mature most late. As will be shown below, the gradual maturation of the structures of the cerebral cortex determines the age characteristics of higher nerve functions and behavioral reactions of children of preschool and primary school age.