What organs make up the central nervous system. What is the CNS? Central nervous system: functions, characteristics, anatomy. Principles of coordination activity

CNS - what is it? The structure of the human nervous system is described as an extensive electrical network. Perhaps this is the most accurate metaphor possible, since a current really runs through thin threads-fibers. Our cells themselves generate microdischarges in order to quickly deliver information from receptors and sensory organs to the brain. But the system does not function by chance, everything is subject to a strict hierarchy. That is why they single out

Departments of the central nervous system

Let's consider this system in more detail. And yet, the central nervous system - what is it? Medicine provides an exhaustive answer to this question. This is the main part of the nervous system of chordates and humans. It consists of structural units - neurons. In invertebrates, this whole structure is similar to a cluster of nodules that do not have a clear subordination to each other.

The human central nervous system is represented by a bundle of the brain and spinal cord. In the latter, the cervical, thoracic, lumbar and sacrococcygeal regions are distinguished. They are located in the corresponding parts of the body. Almost all peripheral nerve impulses are conducted to the spinal cord.

The brain is also divided into several parts, each of which has a specific function, but coordinates their work with the neocortex, or the cerebral cortex. So, anatomically distinguish:

• brain stem;
• medulla;
• hindbrain (pons and cerebellum);
• midbrain (lamina of the quadrigemina and legs of the brain);
• forebrain

Each of these parts will be discussed in more detail below. Such a structure of the nervous system was formed in the process of human evolution so that he could ensure his existence in the new conditions of life.

Spinal cord

It is one of the two organs of the CNS. The physiology of its work does not differ from that in the brain: with the help of complex chemical compounds (neurotransmitters) and the laws of physics (in particular, electricity), information from small branches of nerves is combined into large trunks and either realized in the form of reflexes in the corresponding section of the spinal cord, or enters the brain for further processing.

It is located in the hole between the arches and the bodies of the vertebrae. It is protected, like the head, by three shells: hard, arachnoid and soft. The space between these tissue sheets is filled with a fluid that nourishes the nervous tissue, and also acts as a shock absorber (muffles vibrations during movements). The spinal cord starts from the opening in the occipital bone, on the border with the medulla oblongata, and ends at the level of the first or second lumbar vertebra. Further there are only membranes, cerebrospinal fluid and long nerve fibers ("ponytail"). Conventionally, anatomists divide it into departments and segments.

On the sides of each segment (corresponding to the height of the vertebrae), sensory and motor nerve fibers, called roots, depart. These are long processes of neurons whose bodies are located directly in the spinal cord. They are a collector of information from other parts of the body.

Medulla

The medulla oblongata is also active. It is part of such a formation as the brain stem, and is in direct contact with the spinal cord. There is a conditional boundary between these anatomical formations - this is a decussation. It is separated from the bridge by a transverse groove and a section of the auditory pathways that pass in the rhomboid fossa.

In the thickness of the medulla oblongata are the nuclei of the 9th, 10th, 11th and 12th cranial nerves, fibers of the ascending and descending nerve pathways and the reticular formation. This area is responsible for the implementation of protective reflexes, such as sneezing, coughing, vomiting and others. It also keeps us alive by regulating our breathing and heartbeat. In addition, the medulla oblongata contains centers for regulating muscle tone and maintaining posture.

Bridge

Together with the cerebellum, it is the posterior part of the CNS. What is it? An accumulation of neurons and their processes located between the transverse sulcus and the exit point of the fourth pair of cranial nerves. It is a roller-shaped thickening with a depression in the center (there are vessels in it). From the middle of the bridge exit the fibers of the trigeminal nerve. In addition, the upper and middle cerebellar peduncles depart from the bridge, and the nuclei of the 8th, 7th, 6th and 5th pairs of cranial nerves, the auditory pathway and the reticular formation are located in the upper part of the Varoliev bridge.

The main function of the bridge is to transmit information to the higher and lower parts of the central nervous system. Many ascending and descending paths pass through it, which end or begin their journey in different parts of the cerebral cortex.

Cerebellum

This is a department of the CNS (central nervous system), which is responsible for coordinating movements, maintaining balance and maintaining muscle tone. It is located between the pons and the midbrain. To obtain information about the environment, it has three pairs of legs in which nerve fibers pass.

The cerebellum acts as an intermediate collector of all information. It receives signals from sensory fibers of the spinal cord, as well as from motor fibers starting in the cortex. After analyzing the received data, the cerebellum sends impulses to the motor centers and corrects the position of the body in space. All this happens so quickly and smoothly that we do not notice his work. All our dynamic automatisms (dancing, playing musical instruments, writing) are the responsibility of the cerebellum.

midbrain

In the human CNS there is a department that is responsible for visual perception. It is the midbrain. It consists of two parts:

• The lower one is the legs of the brain, in which the pyramidal pathways pass.
• The upper one is the plate of the quadrigemina, on which, in fact, the visual and auditory centers are located.

The formations in the upper part are closely connected with the diencephalon, so there is not even an anatomical boundary between them. It can be conditionally assumed that this is the posterior commissure of the cerebral hemispheres. In the depths of the midbrain are the nuclei of the third cranial nerve - the oculomotor, and besides this, the red nucleus (it is responsible for controlling movements), the black substance (initiates movements) and the reticular formation.

The main functions of this area of ​​the CNS:

• orienting reflexes (reaction to strong stimuli: light, sound, pain, etc.);
• vision;
• pupil reaction to light and accommodation;
• friendly turn of the head and eyes;
• maintenance of skeletal muscle tone.

diencephalon

This formation is located above the midbrain, immediately below the corpus callosum. It consists of the thalamic part, the hypothalamus and the third ventricle. The thalamic part includes the thalamus proper (or thalamus), the epithalamus, and the metathalamus.

• The thalamus is the center of all types of sensitivity; it collects all afferent impulses and redistributes them into the corresponding motor pathways.
• The epithalamus (pineal gland, or pineal gland) is an endocrine gland. Its main function is the regulation of human biorhythms.
• The metathalamus is formed by the medial and lateral geniculate bodies. The medial bodies represent the subcortical center of hearing, and the lateral bodies represent vision.

The hypothalamus controls the pituitary gland and other endocrine glands. In addition, it regulates partly the autonomic nervous system. For the speed of metabolism and maintenance of body temperature, we must thank him. The third ventricle is a narrow cavity that contains the fluid necessary to feed the central nervous system.

The cortex of the hemispheres

Neocortex CNS - what is it? This is the youngest part of the nervous system, phylo - and ontogenetically it is one of the last to be formed and represents rows of cells densely layered on top of each other. This area occupies about half of the entire space of the cerebral hemispheres. It contains convolutions and furrows.

There are five parts of the cortex: frontal, parietal, temporal, occipital and insular. Each of them is responsible for their area of ​​work. For example, in the frontal lobe are the centers of movement and emotions. In the parietal and temporal - the centers of writing, speech, small and complex movements, in the occipital - visual and auditory, and the insular lobe corresponds to balance and coordination.

All information that is perceived by the endings of the peripheral nervous system, whether it be smell, taste, temperature, pressure or anything else, enters the cerebral cortex and is carefully processed. This process is so automated that when, in view of pathological changes, it stops or gets upset, the person becomes disabled.

CNS functions

For such a complex formation as the central nervous system, the functions corresponding to it are also characteristic. The first of them is integrative-coordinating. It implies the coordinated work of various organs and systems of the body to maintain the constancy of the internal environment. The next function is the connection between a person and his environment, adequate reactions of the body to physical, chemical or biological stimuli. It also includes social activities.

The functions of the central nervous system also cover metabolic processes, their speed, quality and quantity. To do this, there are separate structures, such as the hypothalamus and pituitary gland. Higher mental activity is also possible only thanks to the central nervous system. When the cortex dies, the so-called “social death” is observed, when the human body still remains viable, but as a member of society it no longer exists (it cannot speak, read, write and perceive other information, as well as reproduce it).

It is difficult to imagine humans and other animals without the central nervous system. Its physiology is complex and not yet fully understood. Scientists are trying to figure out how the most complex biological computer ever worked. But this is like "a bunch of atoms studying other atoms," so advances in this area are not yet sufficient.

Topic. Structure and functions of the human nervous system

1 What is the nervous system

2 Central nervous system

Brain

Spinal cord

CNS

3 Autonomic nervous system

4 Development of the nervous system in ontogeny. Characteristics of the three-bubble and five-bubble stages of brain formation

What is the nervous system

Nervous system is a system that regulates the activity of all human organs and systems. This system causes:

1) the functional unity of all human organs and systems;

2) the connection of the whole organism with the environment.

Nervous system controls the activity of various organs, systems and apparatuses that make up the body. It regulates the functions of movement, digestion, respiration, blood supply, metabolic processes, etc. The nervous system establishes the relationship of the body with the external environment, unites all parts of the body into a single whole.

The nervous system according to the topographic principle is divided into central and peripheral ( rice. one).

central nervous system(CNS) includes the brain and spinal cord.

To peripheral part of the nervoussystems include spinal and cranial nerves with their roots and branches, nerve plexuses, nerve nodes, nerve endings.

In addition, the nervous system containstwo special parts : somatic (animal) and vegetative (autonomous).

somatic nervous system innervates mainly the organs of the soma (body): striated (skeletal) muscles (face, trunk, limbs), skin and some internal organs (tongue, larynx, pharynx). The somatic nervous system primarily performs the functions of connecting the body with the external environment, providing sensitivity and movement, causing contraction of the skeletal muscles. Since the functions of movement and feeling are characteristic of animals and distinguish them from plants, this part of the nervous system is calledanimal(animal). The actions of the somatic nervous system are controlled by human consciousness.

autonomic nervous system innervates the viscera, glands, smooth muscles of organs and skin, blood vessels and the heart, regulates metabolic processes in tissues. The autonomic nervous system influences the processes of the so-called plant life, common to animals and plants(metabolism, respiration, excretion, etc.), which is why its name comes from ( vegetative- vegetable).

Both systems are closely related, but the autonomic nervous system has some degree of autonomy and does not depend on our will, as a result of which it is also called autonomic nervous system.

She is being divided into two parts sympathetic and parasympathetic. The allocation of these departments is based both on the anatomical principle (differences in the location of the centers and the structure of the peripheral part of the sympathetic and parasympathetic nervous system), and on functional differences.

Excitation of the sympathetic nervous system contributes to the intensive activity of the body; excitation of the parasympathetic On the contrary, it helps to restore the resources expended by the body.

The sympathetic and parasympathetic systems have opposite influence on many organs, being functional antagonists. Yes, under influence of impulses coming along the sympathetic nerves, heart contractions become more frequent and intensified, blood pressure in the arteries rises, glycogen in the liver and muscles breaks down, blood glucose increases, pupils dilate, sensitivity of the sense organs and the efficiency of the central nervous system increase, bronchi narrow, contractions of the stomach and intestines are inhibited, secretion decreases gastric juice and pancreatic juice, the bladder relaxes and its emptying is delayed. Under the influence of impulses coming through the parasympathetic nerves, heart contractions slow down and weaken, blood pressure decreases, blood glucose decreases, contractions of the stomach and intestines are stimulated, secretion of gastric juice and pancreatic juice increases, etc.

central nervous system

Central nervous system (CNS)- the main part of the nervous system of animals and humans, consisting of a cluster of nerve cells (neurons) and their processes.

central nervous system consists of the brain and spinal cord and their protective membranes.

The outermost is dura mater , below it is located arachnoid (arachnoid ), and then pia mater fused to the surface of the brain. Between the soft and arachnoid membranes is subarachnoid (subarachnoid) space , containing cerebrospinal (cerebrospinal) fluid, in which both the brain and spinal cord literally float. The action of the buoyancy force of the fluid leads to the fact that, for example, the adult brain, which has an average weight of 1500 g, actually weighs 50–100 g inside the skull. The meninges and cerebrospinal fluid also play the role of shock absorbers, softening all kinds of shocks and shocks that experiences the body and which could cause damage to the nervous system.

CNS formed from gray and white matter .

Gray matter make up cell bodies, dendrites and unmyelinated axons, organized into complexes that include countless synapses and serve as information processing centers for many of the functions of the nervous system.

white matter consists of myelinated and unmyelinated axons that act as conductors that transmit impulses from one center to another. The gray and white matter also contain glial cells.

CNS neurons form many circuits that perform two main functions: provide reflex activity, as well as complex information processing in higher brain centers. These higher centers, such as the visual cortex (visual cortex), receive incoming information, process it, and transmit a response signal along the axons.

The result of the activity of the nervous system- this or that activity, which is based on the contraction or relaxation of muscles or the secretion or cessation of secretion of glands. It is with the work of muscles and glands that any way of our self-expression is connected. Incoming sensory information is processed by passing through a sequence of centers connected by long axons, which form specific pathways, such as pain, visual, auditory. sensitive (ascending) pathways go in an upward direction to the centers of the brain. Motor (descending)) paths connect the brain with the motor neurons of the cranial and spinal nerves. Pathways are usually organized in such a way that information (for example, pain or tactile) from the right side of the body goes to the left side of the brain and vice versa. This rule also applies to descending motor pathways: the right half of the brain controls the movements of the left half of the body, and the left half controls the right. There are a few exceptions to this general rule, however.

Brain

consists of three main structures: the cerebral hemispheres, the cerebellum and the trunk.

Large hemispheres - the largest part of the brain - contain higher nerve centers that form the basis of consciousness, intellect, personality, speech, understanding. In each of the large hemispheres, the following formations are distinguished: isolated accumulations (nuclei) of gray matter lying in the depths, which contain many important centers; a large array of white matter located above them; covering the hemispheres from the outside, a thick layer of gray matter with numerous convolutions, constituting the cerebral cortex.

Cerebellum also consists of a gray matter located in the depths, an intermediate array of white matter and an outer thick layer of gray matter, forming many convolutions. The cerebellum provides mainly coordination of movements.

Trunk The brain is formed by a mass of gray and white matter, not divided into layers. The trunk is closely connected with the cerebral hemispheres, cerebellum and spinal cord and contains numerous centers of sensory and motor pathways. The first two pairs of cranial nerves depart from the cerebral hemispheres, while the remaining ten pairs from the trunk. The trunk regulates such vital functions as breathing and blood circulation.

Scientists have calculated that the brain of a man is heavier than the brain of a woman by an average of 100 gm. They explain this by the fact that most men are much larger than women in terms of their physical parameters, that is, all parts of a man's body are larger than parts of a woman's body. The brain actively begins to grow even when the child is still in the womb. The brain reaches its "real" size only when a person reaches the age of twenty. At the very end of a person's life, his brain becomes a little lighter.

There are five main divisions in the brain:

1) telencephalon;

2) diencephalon;

3) midbrain;

4) hindbrain;

5) medulla oblongata.

If a person has suffered a traumatic brain injury, then this always negatively affects both his central nervous system and his mental state.

The "drawing" of the brain is very complex. The complexity of this "pattern" is predetermined by the fact that furrows and ridges go along the hemispheres, which form a kind of "gyrus". Despite the fact that this "drawing" is strictly individual, there are several common furrows. Thanks to these common furrows, biologists and anatomists have identified 5 lobes of the hemispheres:

1) frontal lobe;

2) parietal lobe;

3) occipital lobe;

4) temporal lobe;

5) hidden share.

Despite the fact that hundreds of works have been written on the study of the functions of the brain, its nature has not been fully elucidated. One of the most important mysteries that the brain “guesses” is vision. Rather, how and with what help we see. Many mistakenly assume that vision is the prerogative of the eyes. This is not true. Scientists are more inclined to believe that the eyes simply perceive the signals that our environment sends us. Eyes pass them on "by authority". The brain, having received this signal, builds a picture, i.e. we see what our brain “shows” to us. Similarly, the issue with hearing should be resolved: it is not the ears that hear. Rather, they also receive certain signals that the environment sends us.

Spinal cord.

The spinal cord looks like a cord, it is somewhat flattened from front to back. Its size in an adult is approximately 41 to 45 cm, and its weight is about 30 gm. It is "surrounded" by the meninges and is located in the brain canal. Throughout its length, the thickness of the spinal cord is the same. But it has only two thickenings:

1) cervical thickening;

2) lumbar thickening.

It is in these thickenings that the so-called innervation nerves of the upper and lower extremities are formed. Dorsal brainis divided into several departments:

1) cervical;

2) thoracic region;

3) lumbar;

4) sacral department.

Located inside the spinal column and protected by its bone tissue, the spinal cord has a cylindrical shape and is covered with three membranes. On a transverse section, the gray matter has the shape of the letter H or a butterfly. Gray matter is surrounded by white matter. The sensory fibers of the spinal nerves end in the dorsal (posterior) sections of the gray matter - the posterior horns (at the ends of H facing the back). The bodies of motor neurons of the spinal nerves are located in the ventral (anterior) sections of the gray matter - the anterior horns (at the ends of H, remote from the back). In the white matter, there are ascending sensory pathways ending in the gray matter of the spinal cord, and descending motor pathways coming from the gray matter. In addition, many fibers in the white matter connect the different parts of the gray matter of the spinal cord.

Main and specific CNS function- the implementation of simple and complex highly differentiated reflective reactions, called reflexes. In higher animals and humans, the lower and middle sections of the central nervous system - the spinal cord, medulla oblongata, midbrain, diencephalon and cerebellum - regulate the activity of individual organs and systems of a highly developed organism, communicate and interact between them, ensure the unity of the organism and the integrity of its activity. The highest department of the central nervous system - the cerebral cortex and the nearest subcortical formations - mainly regulates the connection and relationship of the body as a whole with the environment.

The main features of the structure and function CNS

connected with all organs and tissues through the peripheral nervous system, which in vertebrates includes cranial nerves from the brain, and spinal nerves- from the spinal cord, intervertebral nerve nodes, as well as the peripheral part of the autonomic nervous system - nerve nodes, with nerve fibers approaching them (preganglionic) and departing from them (postganglionic) nerve fibers.

Sensory, or afferent, nervous adductor fibers carry excitation to the central nervous system from peripheral receptors; by diverting efferent (motor and autonomic) nerve fibers excitation from the central nervous system is sent to the cells of the executive working apparatus (muscles, glands, blood vessels, etc.). In all parts of the CNS there are afferent neurons that perceive stimuli coming from the periphery, and efferent neurons that send nerve impulses to the periphery to various executive organs.

Afferent and efferent cells with their processes can contact each other and make up two-neuron reflex arc, carrying out elementary reflexes (for example, tendon reflexes of the spinal cord). But, as a rule, interneurons, or interneurons, are located in the reflex arc between the afferent and efferent neurons. Communication between different parts of the central nervous system is also carried out with the help of many processes of afferent, efferent and intercalary neurons of these departments, forming intracentral short and long pathways. The CNS also includes neuroglial cells, which perform a supporting function in it, and also participate in the metabolism of nerve cells.

The brain and spinal cord are covered with membranes:

1) dura mater;

2) arachnoid;

3) soft shell.

Hard shell. The hard shell covers the outside of the spinal cord. In its shape, it most of all resembles a bag. It should be said that the outer hard shell of the brain is the periosteum of the bones of the skull.

Arachnoid. The arachnoid is a substance that is almost closely adjacent to the hard shell of the spinal cord. The arachnoid membrane of both the spinal cord and the brain does not contain any blood vessels.

Soft shell. The pia mater of the spinal cord and brain contains nerves and blood vessels, which, in fact, feed both brains.

autonomic nervous system

autonomic nervous system It is one of the parts of our nervous system. The autonomic nervous system is responsible for: the activity of the internal organs, the activity of the endocrine and external secretion glands, the activity of the blood and lymphatic vessels, and also, to some extent, the muscles.

The autonomic nervous system is divided into two sections:

1) sympathetic section;

2) parasympathetic section.

Sympathetic nervous system dilates the pupil, it also causes an increase in heart rate, an increase in blood pressure, expands the small bronchi, etc. This nervous system is carried out by sympathetic spinal centers. It is from these centers that peripheral sympathetic fibers begin, which are located in the lateral horns of the spinal cord.

parasympathetic nervous system is responsible for the activity of the bladder, genitals, rectum, and it also “irritates” a number of other nerves (for example, glossopharyngeal, oculomotor nerve). Such a "diverse" activity of the parasympathetic nervous system is explained by the fact that its nerve centers are located both in the sacral spinal cord and in the brain stem. Now it becomes clear that those nerve centers that are located in the sacral spinal cord control the activity of the organs located in the small pelvis; nerve centers located in the brain stem regulate the activity of other organs through a number of special nerves.

How is the control over the activity of the sympathetic and parasympathetic nervous system carried out? Control over the activity of these sections of the nervous system is carried out by special autonomic apparatus, which are located in the brain.

Diseases of the autonomic nervous system. The causes of diseases of the autonomic nervous system are as follows: a person does not tolerate hot weather or, conversely, feels uncomfortable in winter. A symptom may be that a person, when excited, quickly begins to blush or turn pale, his pulse quickens, he begins to sweat a lot.

It should be noted that diseases of the autonomic nervous system occur in people from birth. Many believe that if a person gets excited and blushes, then he is simply too modest and shy. Few people would think that this person has some kind of autonomic nervous system disease.

Also, these diseases can be acquired. For example, due to a head injury, chronic poisoning with mercury, arsenic, due to a dangerous infectious disease. They can also occur when a person is overworked, with a lack of vitamins, with severe mental disorders and experiences. Also, diseases of the autonomic nervous system can be the result of non-compliance with safety regulations at work with dangerous working conditions.

The regulatory activity of the autonomic nervous system may be impaired. Diseases can "mask" as other diseases. For example, with a disease of the solar plexus, bloating, poor appetite can be observed; with a disease of the cervical or thoracic nodes of the sympathetic trunk, chest pains can be observed, which can radiate to the shoulder. These pains are very similar to heart disease.

To prevent diseases of the autonomic nervous system, a person should follow a number of simple rules:

1) avoid nervous fatigue, colds;

2) observe safety precautions in production with hazardous working conditions;

3) eat well;

4) go to the hospital in a timely manner, complete the entire prescribed course of treatment.

Moreover, the last point, timely admission to the hospital and complete completion of the prescribed course of treatment, is the most important. This follows from the fact that delaying your visit to the doctor for too long can lead to the most unfortunate consequences.

Good nutrition also plays an important role, because a person "charges" his body, gives him new strength. Having refreshed, the body begins to fight diseases several times more actively. In addition, fruits contain many beneficial vitamins that help the body fight disease. The most useful fruits are in their raw form, because when they are harvested, many useful properties can disappear. A number of fruits, in addition to containing vitamin C, also have a substance that enhances the action of vitamin C. This substance is called tannin and is found in quinces, pears, apples, and pomegranates.

Development of the nervous system in ontogeny. Characteristics of the three-bubble and five-bubble stages of brain formation

Ontogeny, or the individual development of an organism, is divided into two periods: prenatal (intrauterine) and postnatal (after birth). The first continues from the moment of conception and the formation of the zygote until birth; the second - from the moment of birth to death.

prenatal period in turn is divided into three periods: initial, embryonic and fetal. The initial (pre-implantation) period in humans covers the first week of development (from the moment of fertilization to implantation in the uterine mucosa). Embryonic (prefetal, embryonic) period - from the beginning of the second week to the end of the eighth week (from the moment of implantation to the completion of organ laying). The fetal (fetal) period begins from the ninth week and lasts until birth. At this time, there is an increased growth of the body.

postnatal period ontogenesis is divided into eleven periods: 1st - 10th day - newborns; 10th day - 1 year - infancy; 1-3 years - early childhood; 4-7 years - the first childhood; 8-12 years - the second childhood; 13-16 years - adolescence; 17-21 years old - youthful age; 22-35 years - the first mature age; 36-60 years - the second mature age; 61-74 years - old age; from 75 years old - senile age, after 90 years old - long-livers.

Ontogeny ends with natural death.

The nervous system develops from three main formations: neural tube, neural crest and neural placodes. The neural tube is formed as a result of neurulation from the neural plate - a section of the ectoderm located above the notochord. According to the theory of Shpemen's organizers, chord blastomeres are capable of secreting substances - inductors of the first kind, as a result of which the neural plate bends inside the body of the embryo and a neural groove is formed, the edges of which then merge, forming a neural tube. The closure of the edges of the neural groove begins in the cervical region of the body of the embryo, spreading first to the caudal part of the body, and later to the cranial.

The neural tube gives rise to the central nervous system, as well as neurons and gliocytes of the retina. Initially, the neural tube is represented by a multi-row neuroepithelium, the cells in it are called ventricular. Their processes facing the cavity of the neural tube are connected by nexuses, the basal parts of the cells lie on the subpial membrane. The nuclei of neuro-epithelial cells change their location depending on the phase of the cell life cycle. Gradually, towards the end of embryogenesis, ventricular cells lose their ability to divide and give rise to neurons and various types of gliocytes in the postnatal period. In some areas of the brain (germinal or cambial zones), ventricular cells do not lose their ability to divide. In this case, they are called subventricular and extraventricular. Of these, in turn, neuroblasts differentiate, which, no longer having the ability to proliferate, undergo changes during which they turn into mature nerve cells - neurons. The difference between neurons and other cells of their differon (cell row) is the presence of neurofibrils in them, as well as processes, while the axon (neuritis) appears first, and later - dendrites. The processes form connections - synapses. In total, the differon of the nervous tissue is represented by neuroepithelial (ventricular), subventricular, extraventricular cells, neuroblasts and neurons.

Unlike macroglial gliocytes, which develop from ventricular cells, microglial cells develop from the mesenchyme and enter the macrophage system.

The cervical and trunk parts of the neural tube give rise to the spinal cord, the cranial part differentiates into the head. The cavity of the neural tube turns into a spinal canal connected to the ventricles of the brain.

The brain undergoes several stages in its development. Its departments develop from the primary cerebral vesicles. At first there are three of them: front, middle and diamond-shaped. By the end of the fourth week, the anterior cerebral vesicle is divided into the rudiments of the telencephalon and diencephalon. Shortly thereafter, the rhomboid bladder also divides, giving rise to the hindbrain and medulla oblongata. This stage of brain development is called the stage of five brain bubbles. The time of their formation coincides with the time of the appearance of the three bends of the brain. First of all, a parietal bend is formed in the region of the middle cerebral bladder, its bulge is turned dorsally. After it, an occipital bend appears between the rudiments of the medulla oblongata and spinal cord. Its convexity is also turned dorsally. The last to form a bridge bend between the two previous ones, but it bends ventrally.

The cavity of the neural tube in the brain is transformed first into the cavity of three, then five bubbles. The cavity of the rhomboid bladder gives rise to the fourth ventricle, which is connected through the aqueduct of the midbrain (the cavity of the middle cerebral bladder) with the third ventricle, formed by the cavity of the rudiment of the diencephalon. The cavity of the initially unpaired rudiment of the telencephalon is connected through the interventricular opening with the cavity of the rudiment of the diencephalon. In the future, the cavity of the terminal bladder will give rise to the lateral ventricles.

The walls of the neural tube at the stages of formation of the cerebral vesicles will thicken most evenly in the region of the midbrain. The ventral part of the neural tube is transformed into the legs of the brain (midbrain), gray tubercle, funnel, posterior pituitary gland (midbrain). Its dorsal part turns into a plate of the roof of the midbrain, as well as the roof of the third ventricle with the choroid plexus and the epiphysis. The lateral walls of the neural tube in the region of the diencephalon grow, forming visual tubercles. Here, under the influence of inductors of the second kind, protrusions are formed - eye vesicles, each of which will give rise to an eye cup, and later - the retina. Inducers of the third kind, located in the eyecups, affect the ectoderm above itself, which laces up inside the glasses, giving rise to the lens.

central nervous system(CNS) - the main part of the nervous system of animals and humans, consisting of an accumulation of nerve cells (neurons) and their processes; it is represented in invertebrates by a system of closely interconnected nerve nodes (ganglia), in vertebrates and humans - by the spinal cord and brain.

The main and specific function of the central nervous system is the implementation of simple and complex highly differentiated reflective, called. In higher animals and humans, the lower and middle sections of the central nervous system -, and - regulate the activity of individual organs and systems of a highly developed organism, communicate and interact between them, ensure the unity of the organism and the integrity of its activities. The highest department of the central nervous system - the cerebral cortex and the nearest subcortical formations - mainly regulates the connection and relationship of the body as a whole with the environment.

The main features of the structure and function

The central nervous system is connected with all organs and tissues through the peripheral nervous system, which in vertebrates includes cranial nerves extending from the brain, and spinal nerves - from, intervertebral nerve nodes, as well as the peripheral part of the autonomic nervous system - nerve nodes, with approaches to him (preganglionic, from the Latin ganglion) and outgoing from them (postganglionic) nerve fibers. Sensitive, or afferent, nerve adductor fibers are carried to the central nervous system from peripheral ones; along the efferent efferent (motor and autonomic) nerve fibers, excitation from the central nervous system is directed to the cells of the executive working apparatus (muscles, glands, blood vessels, etc.). In all parts of the central nervous system there are afferent, perceiving stimuli coming from the periphery, and efferent neurons that send nerve impulses to the periphery to various executive effector organs. Afferent and efferent cells with their processes can contact each other and make up a two-neuron reflex arc that performs elementary reflexes (for example, tendon reflexes). But, as a rule, interneurons, or interneurons, are located in the reflex arc between the afferent and efferent neurons. Communication between different parts of the CNS is also carried out with the help of many processes of afferent, efferent and intercalary neurons of these parts, which form intracentral short and long pathways. The CNS also includes cells that perform a supporting function in it, and also participate in the metabolism of nerve cells.

Explanation for the figure

I. Neck nerves.
II. Thoracic nerves.
III. Lumbar nerves.
IV. sacral nerves.
V. Coccygeal nerves.
-/-
1. Brain.
2. Diencephalon.
3. Midbrain.
4. Bridge.
5. .
6. Medulla oblongata.
7. Spinal cord.
8. Neck thickening.
9. Transverse thickening.
10. "Ponytail"

central nervous system(CNS), when considered in detail, consists of the forebrain, midbrain, hindbrain and spinal cord. In these main sections of the central nervous system, in turn, the most important structures are distinguished that are directly related to mental processes, states and properties of a person: the thalamus, hypothalamus, bridge, cerebellum and medulla oblongata.

Main and specific function CNS- the implementation of simple and complex highly differentiated reflective reactions, called reflexes. In higher animals and humans, the lower and middle sections of the central nervous system - the spinal cord, medulla oblongata, midbrain, diencephalon and cerebellum - regulate the activity of individual organs and systems of a highly developed organism, communicate and interact between them, ensure the unity of the organism and the integrity of its activity. Superior department CNS- the cerebral cortex and the nearest subcortical formations - mainly regulates the connection and relationship of the body as a whole with the environment.
Almost all departments of the central and peripheral nervous system are involved in the processing of information coming through external and internal receptors located on the periphery of the body and in the organs themselves. The work of the cerebral cortex and subcortical structures included in the forebrain is associated with higher mental functions, with thinking and consciousness of a person.

The central nervous system is connected with all organs and tissues of the body through nerves that come out of the brain and spinal cord. They carry information that enters the brain from the external environment and conduct it in the opposite direction to individual parts and organs of the body. Nerve fibers entering the brain from the periphery are called afferent, and those that conduct impulses from the center to the periphery are called efferent.
central nervous system is a collection of nerve cells - neurons. CNS neurons form many circuits that perform two main functions: they provide reflex activity, as well as complex information processing in higher brain centers. These higher centers, such as the visual cortex (visual cortex), receive incoming information, process it, and transmit a response signal along the axons.
Tree-like processes extending from the bodies of nerve cells are called dendrites. One of these processes is elongated and connects the bodies of some neurons with the bodies or dendrites of other neurons. It's called an axon. Part of the axons is covered with a special myelin sheath, which contributes to faster conduction of the impulse along the nerve.
The places where nerve cells meet each other are called synapses. Through them, nerve impulses are transmitted from one cell to another. The mechanism of synaptic impulse transmission, which operates on the basis of biochemical metabolic processes, can facilitate or hinder the passage of nerve impulses through the central nervous system and thereby participate in the regulation of many mental processes and conditions of the body.

CNS connected with all organs and tissues through the peripheral nervous system, which in vertebrates includes cranial nerves extending from the brain, and spinal nerves - from the spinal cord, intervertebral nerve nodes, as well as the peripheral part of the autonomic nervous system - nerve nodes, with suitable to them (preganglionic) and outgoing from them (postganglionic) nerve fibers. Sensitive, or afferent, nerve adductor fibers carry excitation to the central nervous system from peripheral receptors; along the efferent efferent (motor and autonomic) nerve fibers, excitation from the central nervous system is directed to the cells of the executive working apparatus (muscles, glands, blood vessels, etc.). In all departments CNS there are afferent neurons that perceive stimuli coming from the periphery, and efferent neurons that send nerve impulses to the periphery to various executive effector organs. Afferent and efferent cells, with their processes, can contact each other and form a two-neuron reflex arc that performs elementary reflexes (for example, tendon reflexes of the spinal cord). But, as a rule, interneurons, or interneurons, are located in the reflex arc between the afferent and efferent neurons. Communication between different parts of the CNS is also carried out with the help of many processes of afferent, efferent and intercalary neurons of these parts, which form intracentral short and long pathways. Part CNS also includes neuroglial cells that perform a supporting function in it, and also participate in the metabolism of nerve cells.

NERVOUS SYSTEM, a very complex network of structures that permeates the entire body and provides self-regulation of its vital activity due to the ability to respond to external and internal influences (stimuli). The main functions of the nervous system are the receipt, storage and processing of information from the external and internal environment, the regulation and coordination of the activities of all organs and organ systems. In humans, as in mammals, the nervous system includes three main components: 1) nerve cells (neurons); 2) glial cells associated with them, in particular neuroglial cells, as well as cells that form neurilemma; 3) connective tissue. Neurons provide the conduction of nerve impulses; neuroglia performs supporting, protective and trophic functions both in the brain and spinal cord, and neurilemma, which consists mainly of specialized, so-called. Schwann cells, participates in the formation of sheaths of peripheral nerve fibers; connective tissue supports and links together the various parts of the nervous system.

The human nervous system is divided in different ways. Anatomically, it consists of the central nervous system ( CNS) and the peripheral nervous system (PNS). CNS includes the brain and spinal cord, and the PNS, which provides communication between the central nervous system and various parts of the body, includes cranial and spinal nerves, as well as nerve nodes (ganglia) and nerve plexuses that lie outside the spinal cord and brain.
Neuron. The structural and functional unit of the nervous system is a nerve cell - a neuron. It is estimated that there are more than 100 billion neurons in the human nervous system. A typical neuron consists of a body (i.e., a nuclear part) and processes, one usually non-branching process, an axon, and several branching ones, dendrites. The axon carries impulses from the cell body to the muscles, glands, or other neurons, while the dendrites carry them to the cell body.
In a neuron, as in other cells, there is a nucleus and a number of tiny structures - organelles (see also

Central nervous the system consists of dorsal and brain .

The structure and function of the spinal cord. The spinal cord of an adult is a long strand of almost cylindrical shape. The brain is located in the spinal canal. The spinal cord is divided into two symmetrical halves by the anterior and posterior longitudinal grooves. Passes through the center of the spinal cord spinal canal filled with cerebrospinal fluid. It is centered around Gray matter, on a cross section having the shape of a butterfly and formed by the bodies of neurons. The outer layer of the spinal cord is formed white matter, consisting of processes of neurons that form pathways.

On the cross section, the pillars are represented In front of them , rear and lateral horns. In the posterior horns are nuclei of sensory neurons, in the anterior - the neurons that form the motor centers, in the lateral horns lie the neurons that form the centers of the sympathetic part of the autonomic nervous system. 31 pairs of mixed nerves depart from the spinal cord, each of which begins with two roots: in front of him(motor) and rear(sensitive). The anterior roots also contain autonomic nerve fibers. On the back roots are ganglions- accumulations of bodies of sensitive neurons. Connecting, the roots form mixed nerves. Each pair of spinal nerves innervates a specific part of the body.

Functions of the spinal cord:

– reflex- carried out by the somatic and autonomic nervous systems.

– conductive- carried out by the white matter of the ascending and descending pathways.

The structure and functions of the brain.Brain located in the brain part of the skull. The mass of the brain of an adult is about 1400-1500 g. The brain consists of five sections: anterior, middle, posterior, intermediate and oblong. The oldest part of the brain is the medulla oblongata, pons, midbrain and diencephalon. From here come 12 pairs of cranial nerves. This part forms the brain stem. The cerebral hemispheres became evolutionarily later.

Medulla is a continuation of the spinal cord. Performs a reflex and conductive function. The following centers are located in the medulla oblongata:

- respiratory;

- cardiac activity;

- vasomotor;

- unconditioned food reflexes;

- protective reflexes (coughing, sneezing, blinking, tearing);

- centers of change in the tone of some muscle groups and body position.

Hind brain comprises pons and cerebellum. The pontine pathways connect the medulla oblongata with the cerebral hemispheres.

Cerebellum plays a major role in maintaining body balance and coordination of movements. All vertebrates have a cerebellum, but the level of its development depends on the habitat and the nature of the movements performed.

midbrain in the process of evolution has changed less than other departments. Its development is associated with visual and auditory analyzers.

The diencephalon includes: optic tubercles ( thalamus), epithelium ( epithalamus), hypotuberous region ( hypothalamus) and cranked bodies. In it is located reticular formation- a network of neurons and nerve fibers that affects the activity of various parts of the central nervous system.

thalamus is responsible for all types of sensitivity (except olfactory) and coordinates facial expressions, gestures, and other manifestations of emotions. Adjacent to the thalamus epiphysis- gland of internal secretion. The nuclei of the epiphysis are involved in the work of the olfactory analyzer. Below is another endocrine gland - pituitary .

Hypothalamus controls the activity of the autonomic nervous system, regulation of metabolism, homeostasis, sleep and wakefulness, endocrine functions of the body. It combines nervous and humoral regulatory mechanisms into a common neuroendocrine system. The hypothalamus forms a single complex with the pituitary gland, in which it has a controlling role (control of the activity of the anterior pituitary gland). The hypothalamus secretes the hormones vasopressin and oxytocin, which enter the posterior pituitary gland, and from there are carried by the blood.

In the diencephalon are the subcortical centers of vision and hearing.

forebrain consists of the right and left hemispheres connected by the corpus callosum. The gray matter forms the cerebral cortex. The white matter forms the pathways of the hemispheres. The nuclei of gray matter (subcortical structures) are scattered in the white matter.

The cerebral cortex occupies most of the surface of the hemispheres in humans and consists of several layers of cells. The area of ​​the crust is about 2-2.5 thousand cm2. Such a surface is associated with the presence of a large number of furrows and convolutions. Deep grooves divide each hemisphere into 4 lobes: frontal, parietal, temporal and occipital.

The lower surface of the hemispheres is called the base of the brain. The frontal lobes, separated from the parietal lobes by a deep central sulcus, reach the greatest development in humans. Their mass is about 50% of the mass of the brain.

Associative zones of the cerebral cortex are areas of the cerebral cortex in which the analysis and transformation of incoming excitations takes place. The following zones are distinguished:

– motor the zone is located in the anterior central gyrus of the frontal lobe;

– zone of musculoskeletal sensitivity located in the posterior central gyrus of the parietal lobe;

– visual zone located in the occipital lobe;

– auditory zone located in the temporal lobe;

– centers of smell and taste located on the inner surfaces of the temporal and frontal lobes. The association zones of the cortex connect its various areas. They play an important role in the formation of conditioned reflexes.

The activity of all human organs is controlled by the cerebral cortex. Any spinal reflex is carried out with the participation of the cerebral cortex. The bark provides the connection of the organism with the external environment, is the material basis of human mental activity.

The functions of the left and right hemispheres are not equivalent. The right hemisphere is responsible for imaginative thinking, the left - for abstract. With damage to the left hemisphere, human speech is impaired.