The human nervous system is basic. What is the human nervous system: structure and functions of a complex structure. Thus, in the human midbrain there are

All organs and systems of the human body are closely interconnected; they interact through the nervous system, which regulates all mechanisms of life, from digestion to the process of reproduction. It is known that the human body (NS) provides the connection between the human body and the external environment. The unit of the NS is a neuron, which is a nerve cell that conducts impulses to other cells of the body. Connecting into neural circuits, they form an entire system, both somatic and vegetative.

We can say that the NS is plastic, since it is capable of restructuring its work when the needs of the human body change. This mechanism is especially relevant when one of the areas of the brain is damaged.

Since the human nervous system coordinates the work of all organs, its damage affects the activity of both nearby and distant structures, and is accompanied by failure of the functions of organs, tissues and body systems. The causes of disruption of the nervous system may lie in the presence of infections or poisoning of the body, in the occurrence of a tumor or injury, in diseases of the nervous system and metabolic disorders.

Thus, the human nervous system plays a conducting role in the formation and development of the human body. Thanks to the evolutionary improvement of the nervous system, the human psyche and consciousness developed. The nervous system is a vital mechanism for regulating processes that occur in the human body

In the human body, the work of all its organs is closely interconnected, and therefore the body functions as a single whole. The coordination of the functions of internal organs is ensured by the nervous system, which, in addition, communicates the body as a whole with the external environment and controls the functioning of each organ.

Distinguish central nervous system (brain and spinal cord) and peripheral, represented by nerves extending from the brain and spinal cord and other elements lying outside the spinal cord and brain. The entire nervous system is divided into somatic and autonomic (or autonomic). Somatic nervous the system primarily communicates the body with the external environment: perception of irritations, regulation of movements of the striated muscles of the skeleton, etc., vegetative - regulates metabolism and the functioning of internal organs: heartbeat, peristaltic contractions of the intestines, secretion of various glands, etc. Both of them function in close interaction, but the autonomic nervous system has some independence (autonomy), controlling many involuntary functions.

A cross-section of the brain shows that it consists of gray and white matter. Gray matter is a collection of neurons and their short processes. In the spinal cord it is located in the center, surrounding the spinal canal. In the brain, on the contrary, gray matter is located along its surface, forming a cortex and separate clusters called nuclei, concentrated in the white matter. White matter is located under the gray and is composed of nerve fibers covered with membranes. Nerve fibers, when connected, form nerve bundles, and several such bundles form individual nerves. The nerves through which excitation is transmitted from the central nervous system to the organs are called centrifugal, and the nerves that conduct excitation from the periphery to the central nervous system are called centripetal.

The brain and spinal cord are covered with three membranes: dura mater, arachnoid membrane and vascular membrane. Solid - external, connective tissue, lining the internal cavity of the skull and spinal canal. Arachnoid located under the dura ~ this is a thin shell with a small number of nerves and blood vessels. Vascular the membrane is fused with the brain, extends into the grooves and contains many blood vessels. Between the choroid and arachnoid membranes, cavities filled with brain fluid are formed.

In response to irritation, the nervous tissue enters a state of excitation, which is a nervous process that causes or enhances the activity of the organ. The property of nervous tissue to transmit excitation is called conductivity. The speed of excitation is significant: from 0.5 to 100 m/s, therefore, interaction is quickly established between organs and systems that meets the needs of the body. Excitation is carried out along the nerve fibers in isolation and does not pass from one fiber to another, which is prevented by the membranes covering the nerve fibers.

The activity of the nervous system is reflexive character. The response to stimulation carried out by the nervous system is called reflex. The path along which nervous excitation is perceived and transmitted to the working organ is called reflex arc. It consists of five sections: 1) receptors that perceive irritation; 2) sensitive (centripetal) nerve, transmitting excitation to the center; 3) the nerve center, where excitation switches from sensory neurons to motor neurons; 4) motor (centrifugal) nerve, carrying excitation from the central nervous system to the working organ; 5) a working organ that reacts to the received irritation.

The process of inhibition is the opposite of excitation: it stops activity, weakens or prevents its occurrence. Excitation in some centers of the nervous system is accompanied by inhibition in others: nerve impulses entering the central nervous system can delay certain reflexes. Both processes are excitation And braking - are interconnected, which ensures coordinated activity of organs and the entire organism as a whole. For example, during walking, contraction of the flexor and extensor muscles alternates: when the flexion center is excited, impulses follow to the flexor muscles, at the same time, the extension center is inhibited and does not send impulses to the extensor muscles, as a result of which the latter relax, and vice versa.

Spinal cord is located in the spinal canal and has the appearance of a white cord stretching from the occipital foramen to the lower back. There are longitudinal grooves along the anterior and posterior surfaces of the spinal cord; the spinal canal runs in the center, around which the Gray matter - an accumulation of a huge number of nerve cells that form a butterfly outline. Along the outer surface of the spinal cord there is white matter - a cluster of bundles of long processes of nerve cells.

In the gray matter, anterior, posterior and lateral horns are distinguished. They lie in the anterior horns motor neurons, in the rear - insert, which communicate between sensory and motor neurons. Sensory neurons lie outside the cord, in the spinal ganglia along the sensory nerves. Long processes extend from the motor neurons of the anterior horns - anterior roots, forming motor nerve fibers. Axons of sensory neurons approach the dorsal horns, forming back roots, which enter the spinal cord and transmit excitation from the periphery to the spinal cord. Here the excitation is switched to the interneuron, and from it to the short processes of the motor neuron, from which it is then communicated to the working organ along the axon.

In the intervertebral foramina, the motor and sensory roots are connected, forming mixed nerves, which then split into front and rear branches. Each of them consists of sensory and motor nerve fibers. Thus, at the level of each vertebra from the spinal cord in both directions only 31 pairs leave mixed type spinal nerves. The white matter of the spinal cord forms pathways that stretch along the spinal cord, connecting both its individual segments with each other and the spinal cord with the brain. Some pathways are called ascending or sensitive, transmitting excitation to the brain, others - downward or motor, which conduct impulses from the brain to certain segments of the spinal cord.

Function of the spinal cord. The spinal cord performs two functions - reflex and conduction.

Each reflex is carried out by a strictly defined part of the central nervous system - the nerve center. A nerve center is a collection of nerve cells located in one of the parts of the brain and regulating the activity of an organ or system. For example, the center of the knee reflex is located in the lumbar spinal cord, the center of urination is in the sacral, and the center of pupil dilation is in the upper thoracic segment of the spinal cord. The vital motor center of the diaphragm is localized in the III-IV cervical segments. Other centers - respiratory, vasomotor - are located in the medulla oblongata. In the future, some more nerve centers that control certain aspects of the body’s life will be considered. The nerve center consists of many interneurons. It processes the information that comes from the corresponding receptors and generates impulses that are transmitted to the executive organs - the heart, blood vessels, skeletal muscles, glands, etc. As a result, their functional state changes. To regulate the reflex and its accuracy, the participation of the higher parts of the central nervous system, including the cerebral cortex, is necessary.

The nerve centers of the spinal cord are directly connected to the receptors and executive organs of the body. Motor neurons of the spinal cord provide contraction of the muscles of the trunk and limbs, as well as the respiratory muscles - the diaphragm and intercostal muscles. In addition to the motor centers of skeletal muscles, the spinal cord contains a number of autonomic centers.

Another function of the spinal cord is conduction. Bundles of nerve fibers that form white matter connect various parts of the spinal cord to each other and the brain to the spinal cord. There are ascending pathways that carry impulses to the brain, and descending pathways that carry impulses from the brain to the spinal cord. According to the first, excitation arising in the receptors of the skin, muscles, and internal organs is carried along the spinal nerves to the dorsal roots of the spinal cord, perceived by sensitive neurons of the spinal nodes and from here sent either to the dorsal horns of the spinal cord, or as part of the white matter reaches the trunk, and then the cerebral cortex. Descending pathways carry excitation from the brain to the motor neurons of the spinal cord. From here, excitation is transmitted along the spinal nerves to the executive organs.

The activity of the spinal cord is controlled by the brain, which regulates spinal reflexes.

Brain located in the brain part of the skull. Its average weight is 1300-1400 g. After a person is born, brain growth continues up to 20 years. It consists of five sections: the anterior (cerebral hemispheres), intermediate, middle "hindbrain and medulla oblongata. Inside the brain there are four interconnected cavities - cerebral ventricles. They are filled with cerebrospinal fluid. The first and second ventricles are located in the cerebral hemispheres, the third - in the diencephalon, and the fourth - in the medulla oblongata. The hemispheres (the newest part in evolutionary terms) reach a high level of development in humans, making up 80% of the mass of the brain. The phylogenetically more ancient part is the brain stem. The trunk includes the medulla oblongata, pons, midbrain and diencephalon. The white matter of the trunk contains numerous nuclei of gray matter. The nuclei of 12 pairs of cranial nerves also lie in the brain stem. The brainstem is covered by the cerebral hemispheres.

The medulla oblongata is a continuation of the spinal cord and repeats its structure: there are also grooves on the anterior and posterior surfaces. It consists of white matter (conducting bundles), where clusters of gray matter are scattered - the nuclei from which cranial nerves originate - from the IX to the XII pairs, including the glossopharyngeal (IX pair), vagus (X pair), innervating the respiratory organs, blood circulation, digestion and other systems, sublingual (XII pair).. At the top, the medulla oblongata continues into a thickening - pons, and from the sides why the lower cerebellar peduncles extend. From above and from the sides, almost the entire medulla oblongata is covered by the cerebral hemispheres and the cerebellum.

The gray matter of the medulla oblongata contains vital centers that regulate cardiac activity, breathing, swallowing, carrying out protective reflexes (sneezing, coughing, vomiting, lacrimation), secretion of saliva, gastric and pancreatic juice, etc. Damage to the medulla oblongata can cause death due to cessation of cardiac activity and respiration.

The hindbrain includes the pons and cerebellum. Pons It is bounded below by the medulla oblongata, from above it passes into the cerebral peduncles, and its lateral sections form the middle cerebellar peduncles. The substance of the pons contains the nuclei of the V to VIII pairs of cranial nerves (trigeminal, abducens, facial, auditory).

Cerebellum located posterior to the pons and medulla oblongata. Its surface consists of gray matter (cortex). Under the cerebellar cortex there is white matter, in which there are accumulations of gray matter - the nuclei. The entire cerebellum is represented by two hemispheres, the middle part - the vermis and three pairs of legs formed by nerve fibers, through which it is connected to other parts of the brain. The main function of the cerebellum is unconditioned reflex coordination of movements, which determines their clarity, smoothness and preservation of body balance, as well as maintaining muscle tone. Through the spinal cord, along the pathways, impulses from the cerebellum enter the muscles.

The cerebral cortex controls the activity of the cerebellum. The midbrain is located in front of the pons and is represented by quadrigeminal And legs of the brain. In its center there is a narrow canal (brain aqueduct), which connects the III and IV ventricles. The cerebral aqueduct is surrounded by gray matter, in which the nuclei of the III and IV pairs of cranial nerves lie. In the cerebral peduncles the pathways from the medulla oblongata continue; pons to the cerebral hemispheres. The midbrain plays an important role in the regulation of tone and in the implementation of reflexes that make standing and walking possible. The sensitive nuclei of the midbrain are located in the quadrigeminal tubercles: the upper ones contain nuclei associated with the organs of vision, and the lower ones contain nuclei associated with the organs of hearing. With their participation, orienting reflexes to light and sound are carried out.

The diencephalon occupies the highest position in the brainstem and lies anterior to the cerebral peduncles. Consists of two visual tuberosities, supracubertal, subtubercular region and geniculate bodies. Along the periphery of the diencephalon there is white matter, and in its thickness there are nuclei of gray matter. Visual tuberosities - the main subcortical centers of sensitivity: impulses from all receptors of the body arrive here along the ascending pathways, and from here to the cerebral cortex. In the sub-hillock part (hypothalamus) there are centers, the totality of which represents the highest subcortical center of the autonomic nervous system, regulating metabolism in the body, heat transfer, and the constancy of the internal environment. The parasympathetic centers are located in the anterior parts of the hypothalamus, and the sympathetic centers in the posterior parts. The subcortical visual and auditory centers are concentrated in the nuclei of the geniculate bodies.

The second pair of cranial nerves, the optic ones, goes to the geniculate bodies. The brain stem is connected to the environment and to the organs of the body by cranial nerves. By their nature they can be sensitive (I, II, VIII pairs), motor (III, IV, VI, XI, XII pairs) and mixed (V, VII, IX, X pairs).

Autonomic nervous system. Centrifugal nerve fibers are divided into somatic and autonomic. Somatic conduct impulses to skeletal striated muscles, causing them to contract. They originate from motor centers located in the brainstem, in the anterior horns of all segments of the spinal cord and, without interruption, reach the executive organs. Centrifugal nerve fibers going to internal organs and systems, to all tissues of the body, are called vegetative. Centrifugal neurons of the autonomic nervous system lie outside the brain and spinal cord - in the peripheral nerve nodes - ganglia. The processes of ganglion cells end in smooth muscle, cardiac muscle and glands.

The function of the autonomic nervous system is to regulate physiological processes in the body, to ensure the body's adaptation to changing environmental conditions.

The autonomic nervous system does not have its own special sensory pathways. Sensitive impulses from organs are sent along sensory fibers common to the somatic and autonomic nervous systems. The regulation of the autonomic nervous system is carried out by the cerebral cortex.

The autonomic nervous system consists of two parts: sympathetic and parasympathetic. Nuclei of the sympathetic nervous system located in the lateral horns of the spinal cord, from the 1st thoracic to the 3rd lumbar segments. Sympathetic fibers leave the spinal cord as part of the anterior roots and then enter the nodes, which, connected by short bundles in a chain, form a paired border trunk located on both sides of the spinal column. Next, from these nodes, the nerves go to the organs, forming plexuses. Impulses entering the organs through sympathetic fibers provide reflex regulation of their activity. They strengthen and increase heart rate, cause rapid redistribution of blood by narrowing some vessels and dilating others.

Parasympathetic nerve nuclei lie in the middle, medulla oblongata and sacral parts of the spinal cord. Unlike the sympathetic nervous system, all parasympathetic nerves reach peripheral nerve nodes located in the internal organs or on the approaches to them. The impulses conducted by these nerves cause a weakening and slowing of cardiac activity, a narrowing of the coronary vessels of the heart and brain vessels, dilation of the vessels of the salivary and other digestive glands, which stimulates the secretion of these glands, and increases the contraction of the muscles of the stomach and intestines.

Most internal organs receive dual autonomic innervation, that is, they are approached by both sympathetic and parasympathetic nerve fibers, which function in close interaction, exerting the opposite effect on the organs. This is of great importance in adapting the body to constantly changing environmental conditions.

The forebrain consists of highly developed hemispheres and the middle part connecting them. The right and left hemispheres are separated from each other by a deep fissure at the bottom of which lies the corpus callosum. Corpus callosum connects both hemispheres through long processes of neurons that form pathways. The cavities of the hemispheres are represented lateral ventricles(I and II). The surface of the hemispheres is formed by gray matter or the cerebral cortex, represented by neurons and their processes; under the cortex lies white matter - pathways. Pathways connect individual centers within one hemisphere, or the right and left halves of the brain and spinal cord, or different floors of the central nervous system. The white matter also contains clusters of nerve cells that form the subcortical nuclei of the gray matter. Part of the cerebral hemispheres is the olfactory brain with a pair of olfactory nerves extending from it (I pair).

The total surface of the cerebral cortex is 2000 - 2500 cm 2, its thickness is 2.5 - 3 mm. The cortex includes more than 14 billion nerve cells arranged in six layers. In a three-month-old embryo, the surface of the hemispheres is smooth, but the cortex grows faster than the braincase, so the cortex forms folds - convolutions, limited by grooves; they contain about 70% of the surface of the cortex. Furrows divide the surface of the hemispheres into lobes. Each hemisphere has four lobes: frontal, parietal, temporal And occipital, The deepest grooves are the central ones, separating the frontal lobes from the parietal lobes, and the lateral ones, which delimit the temporal lobes from the rest; The parieto-occipital sulcus separates the parietal lobe from the occipital lobe (Fig. 85). Anterior to the central sulcus in the frontal lobe is the anterior central gyrus, behind it is the posterior central gyrus. The lower surface of the hemispheres and the brain stem is called base of the brain.

To understand how the cerebral cortex functions, you need to remember that the human body has a large number of different highly specialized receptors. Receptors are capable of detecting the most minor changes in the external and internal environment.

Receptors located in the skin respond to changes in the external environment. In muscles and tendons there are receptors that signal to the brain about the degree of muscle tension and joint movements. There are receptors that respond to changes in the chemical and gas composition of the blood, osmotic pressure, temperature, etc. In the receptor, irritation is converted into nerve impulses. Along sensitive nerve pathways, impulses are carried to the corresponding sensitive zones of the cerebral cortex, where a specific sensation is formed - visual, olfactory, etc.

The functional system, consisting of a receptor, a sensitive pathway and a zone of the cortex where this type of sensitivity is projected, was called by I. P. Pavlov analyzer.

Analysis and synthesis of the received information is carried out in a strictly defined area - the zone of the cerebral cortex. The most important areas of the cortex are motor, sensitive, visual, auditory, and olfactory. Motor the zone is located in the anterior central gyrus in front of the central sulcus of the frontal lobe, the zone skin-muscular sensitivity - behind the central sulcus, in the posterior central gyrus of the parietal lobe. Visual the zone is concentrated in the occipital lobe, auditory - in the superior temporal gyrus of the temporal lobe, and olfactory And gustatory zones - in the anterior temporal lobe.

The activity of analyzers reflects the external material world in our consciousness. This enables mammals to adapt to environmental conditions by changing behavior. Man, learning natural phenomena, the laws of nature and creating tools, actively changes the external environment, adapting it to his needs.

Many neural processes take place in the cerebral cortex. Their purpose is twofold: interaction of the body with the external environment (behavioral reactions) and the unification of body functions, nervous regulation of all organs. The activity of the cerebral cortex of humans and higher animals was defined by I. P. Pavlov as higher nervous activity, representing conditioned reflex function cerebral cortex. Even earlier, the main principles about the reflex activity of the brain were expressed by I. M. Sechenov in his work “Reflexes of the Brain.” However, the modern idea of higher nervous activity was created by I.P. Pavlov, who, by studying conditioned reflexes, substantiated the mechanisms of adaptation of the body to changing environmental conditions.

Conditioned reflexes are developed during the individual life of animals and humans. Therefore, conditioned reflexes are strictly individual: some individuals may have them, while others may not. For such reflexes to occur, the action of the conditioned stimulus must coincide in time with the action of the unconditioned stimulus. Only the repeated coincidence of these two stimuli leads to the formation of a temporary connection between the two centers. According to the definition of I.P. Pavlov, reflexes acquired by the body during its life and resulting from the combination of indifferent stimuli with unconditioned ones are called conditioned.

In humans and mammals, new conditioned reflexes are formed throughout life; they are locked in the cerebral cortex and are temporary in nature, since they represent temporary connections of the organism with the environmental conditions in which it is located. Conditioned reflexes in mammals and humans are very complex to develop, since they cover a whole complex of stimuli. In this case, connections arise between different parts of the cortex, between the cortex and subcortical centers, etc. The reflex arc becomes significantly more complex and includes receptors that perceive conditioned stimulation, a sensory nerve and the corresponding pathway with subcortical centers, a section of the cortex that perceives conditioned irritation, second area associated with the center of the unconditioned reflex, center of the unconditioned reflex, motor nerve, working organ.

During the individual life of an animal and a person, countless formed conditioned reflexes serve as the basis for his behavior. Animal training is also based on the development of conditioned reflexes, which arise as a result of combination with unconditioned ones (giving treats or encouraging affection) when jumping through a burning ring, lifting on their paws, etc. Training is important in the transportation of goods (dogs, horses), border protection, hunting (dogs), etc.

Various environmental stimuli acting on the body can cause not only the formation of conditioned reflexes in the cortex, but also their inhibition. If inhibition occurs immediately upon the first action of the stimulus, it is called unconditional. When braking, suppression of one reflex creates conditions for the emergence of another. For example, the smell of a predatory animal inhibits the consumption of food by a herbivore and causes an orienting reflex, in which the animal avoids meeting the predator. In this case, in contrast to unconditional inhibition, the animal develops conditioned inhibition. It occurs in the cerebral cortex when a conditioned reflex is reinforced by an unconditioned stimulus and ensures the animal’s coordinated behavior in constantly changing environmental conditions, when useless or even harmful reactions are excluded.

Higher nervous activity. Human behavior is associated with conditioned-unconditioned reflex activity. Based on unconditioned reflexes, starting from the second month after birth, the child develops conditioned reflexes: as he develops, communicates with people and is influenced by the external environment, temporary connections constantly arise in the cerebral hemispheres between their various centers. The main difference between human higher nervous activity is thinking and speech, which appeared as a result of labor social activity. Thanks to the word, generalized concepts and ideas arise, as well as the ability for logical thinking. As a stimulus, a word evokes a large number of conditioned reflexes in a person. They are the basis for training, education, and the development of work skills and habits.

Based on the development of speech function in people, I. P. Pavlov created the doctrine of first and second signaling systems. The first signaling system exists in both humans and animals. This system, the centers of which are located in the cerebral cortex, perceives through receptors direct, specific stimuli (signals) of the external world - objects or phenomena. In humans, they create the material basis for sensations, ideas, perceptions, impressions about the surrounding nature and social environment, and this constitutes the basis concrete thinking. But only in humans there is a second signaling system associated with the function of speech, with the word audible (speech) and visible (writing).

A person can be distracted from the characteristics of individual objects and find common properties in them, which are generalized in concepts and united by one word or another. For example, the word “birds” summarizes representatives of various genera: swallows, tits, ducks and many others. Likewise, every other word acts as a generalization. For a person, a word is not only a combination of sounds or an image of letters, but first of all a form of representing material phenomena and objects of the surrounding world in concepts and thoughts. With the help of words, general concepts are formed. Through the word, signals about specific stimuli are transmitted, and in this case the word serves as a fundamentally new stimulus - signal signals.

When generalizing various phenomena, a person discovers natural connections between them - laws. A person’s ability to generalize is the essence abstract thinking, which distinguishes him from animals. Thinking is the result of the function of the entire cerebral cortex. The second signaling system arose as a result of the joint work of people, in which speech became a means of communication between them. On this basis, verbal human thinking arose and developed further. The human brain is the center of thinking and the center of speech associated with thinking.

The dream and its meaning. According to the teachings of I.P. Pavlov and other domestic scientists, sleep is a deep protective inhibition that prevents overwork and exhaustion of nerve cells. It covers the cerebral hemispheres, midbrain and diencephalon. In

During sleep, the activity of many physiological processes sharply decreases, only the parts of the brain stem that regulate vital functions - breathing, heartbeat - continue to function, but their function is also reduced. The sleep center is located in the hypothalamus of the diencephalon, in the anterior nuclei. The posterior nuclei of the hypothalamus regulate the state of awakening and wakefulness.

Monotonous speech, quiet music, general silence, darkness, and warmth help the body fall asleep. During partial sleep, some “sentinel” points of the cortex remain free from inhibition: the mother sleeps soundly when there is noise, but the slightest rustle of the child wakes her up; soldiers sleep with the roar of guns and even on the march, but immediately respond to the orders of the commander. Sleep reduces the excitability of the nervous system, and therefore restores its functions.

Sleep occurs quickly if stimuli that interfere with the development of inhibition, such as loud music, bright lights, etc., are eliminated.

Using a number of techniques, preserving one excited area, it is possible to induce artificial inhibition in the cerebral cortex (dream-like state) in a person. This condition is called hypnosis. I.P. Pavlov considered it as a partial inhibition of the cortex limited to certain zones. With the onset of the deepest phase of inhibition, weak stimuli (for example, a word) are more effective than strong ones (pain), and high suggestibility is observed. This state of selective inhibition of the cortex is used as a therapeutic technique, during which the doctor instills in the patient that it is necessary to eliminate harmful factors - smoking and drinking alcohol. Sometimes hypnosis can be caused by a strong, unusual stimulus under given conditions. This causes “numbness,” temporary immobilization, and concealment.

Dreams. Both the nature of sleep and the essence of dreams are revealed on the basis of the teachings of I.P. Pavlov: during a person’s wakefulness, excitation processes predominate in the brain, and when all areas of the cortex are inhibited, complete deep sleep develops. With such sleep there are no dreams. In the case of incomplete inhibition, individual uninhibited brain cells and areas of the cortex enter into various interactions with each other. Unlike normal connections in the waking state, they are characterized by quirkiness. Every dream is a more or less vivid and complex event, a picture, a living image that periodically arises in a sleeping person as a result of the activity of cells that remain active during sleep. According to I.M. Sechenov, “dreams are unprecedented combinations of experienced impressions.” Often, external irritations are included in the content of a dream: a warmly covered person sees himself in hot countries, the cooling of his feet is perceived by him as walking on the ground, in the snow, etc. Scientific analysis of dreams from a materialistic point of view has shown the complete failure of the predictive interpretation of “prophetic dreams.”

Hygiene of the nervous system. The functions of the nervous system are carried out by balancing excitatory and inhibitory processes: excitation at some points is accompanied by inhibition at others. At the same time, the functionality of the nervous tissue is restored in the areas of inhibition. Fatigue is promoted by low mobility during mental work and monotony during physical work. Fatigue of the nervous system weakens its regulatory function and can provoke the occurrence of a number of diseases: cardiovascular, gastrointestinal, skin, etc.

The most favorable conditions for the normal functioning of the nervous system are created with the correct alternation of work, active rest and sleep. Elimination of physical fatigue and nervous fatigue occurs when switching from one type of activity to another, in which different groups of nerve cells will alternately experience the load. In conditions of high automation of production, the prevention of overwork is achieved by the personal activity of the employee, his creative interest, and the regular alternation of moments of work and rest.

Drinking alcohol and smoking cause great harm to the nervous system.

The nervous system is the center of nerve communications and the body's most important regulatory system: it organizes and coordinates vital actions. But it has only two main functions: stimulating muscles for movement and regulating the functioning of the body, as well as the endocrine system.

The nervous system is divided into the central nervous system and the peripheral nervous system.

From a functional point of view, the nervous system can be divided into somatic (controlling voluntary actions) and autonomic or autonomic (coordinating involuntary actions) systems.

central nervous system

Includes the spinal cord and brain. Here the cognitive and emotional functions of a person are coordinated. From here all movements are controlled and the weight of feeling is developed.

Brain

In an adult, the brain is one of the heaviest organs in the body, weighing approximately 1300 g.

It is the center of interaction of the nervous system, and its main function is to transmit and respond to received nerve impulses. In its various areas it acts as a mediator of respiratory processes, solving specific problems and hunger.

The brain is divided structurally and functionally into several main parts:

Spinal cord

It is located in the spinal canal and is surrounded by meninges that protect it from injury. In an adult, the length of the spinal cord reaches 42-45 cm and extends from the elongated brain (or the inner part of the brain stem) to the second lumbar vertebra and has a different diameter in different parts of the spine.

31 pairs of peripheral spinal nerves depart from the spinal cord, which connect it to the entire body. Its most important function is to connect various parts of the body to the brain.

Both the brain and spinal cord are protected by three layers of connective tissue. Between the most superficial and middle layers there is a cavity where fluid circulates, which, in addition to protection, also nourishes and cleanses nerve tissue.

Peripheral nervous system

Consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves. It constitutes an intricate network that forms nervous tissue that is not part of the central nervous system and is represented mainly by peripheral nerves responsible for muscles and internal organs.

Cranial nerves

12 pairs of cranial nerves arise from the brain and pass through the openings of the skull.

All cranial nerves are found in the head and neck, with the exception of the tenth nerve (vagus), which also involves various structures of the chest and stomach.

Spinal nerves

Each of the 31 pairs of nerves originate in the dorsal M03IC and then pass through the intervertebral foramina. Their names are associated with the place where they originate: 8 cervical, 12 thoracic, 5 lumbar, 5 cruciate and 1 coccygeal. After passing through the intervertebral foramen, each branch is divided into 2 branches: the anterior, large one, which stretches into the distance to cover the muscles and skin on the front and sides and the skin of the extremities, and the posterior, smaller one, which covers the muscles and skin of the back. The thoracic spinal nerves also communicate with the sympathetic part of the autonomic nervous system. At the top of the neck, the roots of these nerves are very short and located horizontally.

The nervous system is an integral morphological and functional set of various interconnected nervous structures, which, together with the humoral system, ensures the interconnected regulation of the activity of all body systems and the response to changing conditions of the internal and external environment. The nervous system consists of neurons, or nerve cells, and neuroglial cells (neuroglia). Neurons are the main structural and functional elements in both the central and peripheral nervous systems. Neurons- these are excitable cells, that is, they are capable of generating and transmitting electrical impulses (action potentials). Neurons have different shapes and sizes and form processes of two types: axons And dendrites. A neuron usually has several short branched dendrites, along which impulses travel to the neuron body, and one long axon, along which impulses travel from the neuron body to other cells (neurons, muscle or glandular cells). The transfer of excitation from one neuron to other cells occurs through specialized contacts - synapses. Neuroglial cells are more numerous than neurons and make up at least half the volume of the central nervous system, but unlike neurons they cannot generate action potentials. Neuroglial cells are different in structure and origin; they perform auxiliary functions in the nervous system, providing support, trophic, secretory, delimitation and protective functions. According to their functional purpose, they are distinguished 1) somatic or animal nervous system, 2) autonomic or autonomic nervous system.

In turn, in the autonomic nervous system there are:

Sympathetic division of the autonomic nervous system
Parasympathetic division of the autonomic nervous system,
Metasympathetic division of the autonomic nervous system (enteric nervous system).

The central nervous system (CNS) is the main part of the nervous system of animals and humans, consisting of a collection 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 reactions, called. 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, carry out communication and interaction between them, ensure the unity of the organism and the integrity of its activities. The higher 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 central nervous system is connected to 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 ganglia, as well as the peripheral part of the autonomic nervous system - nerve ganglia, with them (preganglionic) and the nerve fibers extending from them (postganglionic). 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 parts of the central nervous system 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 carries out elementary reflexes (for example, tendon reflexes of the spinal cord). But, as a rule, intercalary nerve cells, 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 using many processes of afferent, efferent and intercalary neurons of these parts, 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 autonomic nervous system is a part of the nervous system that has a two-neuron structure and innervates internal organs, smooth muscles, heart, endocrine glands and skin;

Through the autonomic nervous system, the central nervous system regulates the functions of internal organs, blood supply and trophism of all organs. The autonomic nervous system is divided into sympathetic and parasympathetic divisions.

The sympathetic nervous system is the peripheral part of the autonomic nervous system, ensuring the mobilization of the body's resources to perform urgent work. The sympathetic nervous system stimulates the heart, constricts blood vessels and enhances the performance of skeletal muscles. The sympathetic nervous system is represented by:

gray matter of the lateral horns of the spinal cord;
two symmetrical sympathetic trunks with their ganglia;
internodal and connecting branches; and
branches and ganglia involved in the formation of nerve plexuses.

The parasympathetic nervous system is the peripheral part of the autonomic nervous system, responsible for maintaining a constant internal environment of the body. The parasympathetic nervous system consists of:

the cranial region, in which preganglionic fibers leave the midbrain and rhombencephalon as part of several cranial nerves; And
the sacral region, in which preganglionic fibers exit the spinal cord as part of its ventral roots.

The parasympathetic nervous system slows down the heart and dilates some blood vessels.

Main directions of research of the nervous system

Modern science of the nervous system combines many scientific disciplines: along with classical neuroanatomy, neurology and neurophysiology, molecular biology and genetics, chemistry, cybernetics and a number of other sciences make an important contribution to the study of the nervous system. This interdisciplinary approach to the study of the nervous system is reflected in the term neuroscience. In Russian-language scientific literature, the term “neurobiology” is often used as a synonym. One of the main goals of neuroscience is to understand the processes occurring both at the level of individual neurons and neural networks, the result of which are various mental processes: thinking, emotions, consciousness.<В соответствие с этой задачей изучение нервной системы ведется на разных уровнях организация, начиная с молекулярного и заканчивая изучением сознания, творческих способностей и социального поведения.

LECTURE ON THE TOPIC: HUMAN NERVOUS SYSTEM

Nervous system is a system that regulates the activities of all human organs and systems. This system determines: 1) the functional unity of all human organs and systems; 2) the connection of the whole organism with the environment.

From the point of view of maintaining homeostasis, the nervous system ensures: maintaining the parameters of the internal environment at a given level; inclusion of behavioral responses; adaptation to new conditions if they persist for a long time.

Neuron(nerve cell) - the main structural and functional element of the nervous system; Humans have more than one hundred billion neurons. A neuron consists of a body and processes, usually one long process - an axon and several short branched processes - dendrites. Along dendrites, impulses follow to the cell body, along an axon - from the cell body to other neurons, muscles or glands. Thanks to the processes, neurons contact each other and form neural networks and circles through which nerve impulses circulate.

A neuron is a functional unit of the nervous system. Neurons are susceptible to stimulation, that is, they are capable of being excited and transmitting electrical impulses from receptors to effectors. Based on the direction of impulse transmission, afferent neurons (sensory neurons), efferent neurons (motor neurons) and interneurons are distinguished.

Nervous tissue is called excitable tissue. In response to some impact, a process of excitation arises and spreads in it - rapid recharging of cell membranes. The emergence and propagation of excitation (nerve impulse) is the main way the nervous system carries out its control function.

The main prerequisites for the occurrence of excitation in cells: the existence of an electrical signal on the membrane in a resting state - the resting membrane potential (RMP);

the ability to change the potential by changing the permeability of the membrane for certain ions.

The cell membrane is a semi-permeable biological membrane, it has channels that allow potassium ions to pass through, but there are no channels for intracellular anions, which are retained at the inner surface of the membrane, creating a negative charge of the membrane from the inside, this is the resting membrane potential, which averages - – 70 millivolts (mV). There are 20-50 times more potassium ions in the cell than outside, this is maintained throughout life with the help of membrane pumps (large protein molecules capable of transporting potassium ions from the extracellular environment to the inside). The MPP value is determined by the transfer of potassium ions in two directions:

1. from the outside into the cell under the action of pumps (with a large expenditure of energy);

2. from the cell to the outside by diffusion through membrane channels (without energy consumption).

In the process of excitation, the main role is played by sodium ions, which are always 8-10 times more abundant outside the cell than inside. Sodium channels are closed when the cell is at rest; in order to open them, it is necessary to act on the cell with an adequate stimulus. If the stimulation threshold is reached, the sodium channels open and sodium enters the cell. In thousandths of a second, the membrane charge will first disappear and then change to the opposite - this is the first phase of the action potential (AP) - depolarization. The channels close - the peak of the curve, then the charge is restored on both sides of the membrane (due to potassium channels) - the repolarization stage. The excitation stops and while the cell is at rest, the pumps exchange the sodium that entered the cell for potassium, which left the cell.

An PD evoked at any point in a nerve fiber itself becomes an irritant for neighboring sections of the membrane, causing AP in them, which in turn excite more and more sections of the membrane, thus spreading throughout the entire cell. In fibers covered with myelin, APs will occur only in areas free of myelin. Therefore, the speed of signal propagation increases.

The transfer of excitation from cell to another occurs through a chemical synapse, which is represented by the point of contact of two cells. The synapse is formed by presynaptic and postsynaptic membranes and the synaptic cleft between them. Excitation in the cell resulting from AP reaches the area of the presynaptic membrane where synaptic vesicles are located, from which a special substance, the transmitter, is released. The transmitter entering the gap moves to the postsynaptic membrane and binds to it. Pores open in the membrane for ions, they move into the cell and the process of excitation occurs

Thus, in the cell, the electrical signal is converted into a chemical one, and the chemical signal again into an electrical one. Signal transmission in a synapse occurs more slowly than in a nerve cell, and is also one-sided, since the transmitter is released only through the presynaptic membrane, and can only bind to receptors of the postsynaptic membrane, and not vice versa.

Mediators can cause not only excitation but also inhibition in cells. In this case, pores open on the membrane for ions that strengthen the negative charge that existed on the membrane at rest. One cell can have many synaptic contacts. An example of a mediator between a neuron and a skeletal muscle fiber is acetylcholine.

The nervous system is divided into central nervous system and peripheral nervous system.

In the central nervous system, a distinction is made between the brain, where the main nerve centers and the spinal cord are concentrated, and here there are lower-level centers and pathways to peripheral organs.

Peripheral section - nerves, nerve ganglia, ganglia and plexuses.

The main mechanism of activity of the nervous system is reflex. A reflex is any response of the body to a change in the external or internal environment, which is carried out with the participation of the central nervous system in response to irritation of receptors. The structural basis of the reflex is the reflex arc. It includes five consecutive links:

1 - Receptor - a signaling device that perceives influence;

2 - Afferent neuron – brings a signal from the receptor to the nerve center;

3 - Interneuron – central part of the arc;

4 - Efferent neuron - the signal comes from the central nervous system to the executive structure;

5 - Effector - a muscle or gland performing a certain type of activity

Brain consists of clusters of nerve cell bodies, nerve tracts and blood vessels. Nerve tracts form the white matter of the brain and consist of bundles of nerve fibers that conduct impulses to or from various parts of the gray matter of the brain - nuclei or centers. Pathways connect various nuclei, as well as the brain and spinal cord.

Functionally, the brain can be divided into several sections: the forebrain (consisting of the telencephalon and diencephalon), the midbrain, the hindbrain (consisting of the cerebellum and the pons) and the medulla oblongata. The medulla oblongata, pons, and midbrain are collectively called the brainstem.

Spinal cord located in the spinal canal, reliably protecting it from mechanical damage.

The spinal cord has a segmental structure. Two pairs of anterior and posterior roots extend from each segment, which corresponds to one vertebra. There are 31 pairs of nerves in total.

The dorsal roots are formed by sensory (afferent) neurons, their bodies are located in the ganglia, and the axons enter the spinal cord.

The anterior roots are formed by the axons of efferent (motor) neurons, the bodies of which lie in the spinal cord.

The spinal cord is conventionally divided into four sections - cervical, thoracic, lumbar and sacral. It closes a huge number of reflex arcs, which ensures the regulation of many body functions.

The gray central substance is nerve cells, the white one is nerve fibers.

The nervous system is divided into somatic and autonomic.

TO somatic nervous system (from the Latin word “soma” - body) refers to part of the nervous system (both cell bodies and their processes), which controls the activity of skeletal muscles (body) and sensory organs. This part of the nervous system is largely controlled by our consciousness. That is, we are able to bend or straighten an arm, leg, etc. at will. However, we are unable to consciously stop perceiving, for example, sound signals.

Autonomic nervous system (translated from Latin “vegetative” - plant) is part of the nervous system (both cell bodies and their processes), which controls the processes of metabolism, growth and reproduction of cells, that is, functions common to both animals and plants organisms. The autonomic nervous system is responsible, for example, for the activity of internal organs and blood vessels.

The autonomic nervous system is practically not controlled by consciousness, that is, we are not able to relieve a spasm of the gallbladder at will, stop cell division, stop intestinal activity, dilate or constrict blood vessels