ANATOMY AND HISTOLOGY
The human nervous system is divided into central and peripheral. The central nervous system includes the brain and spinal cord, the peripheral nervous system includes nerve roots, nerve trunks, nerves, nerve plexuses, nerve ganglia (sensory and autonomic), and nerve endings.
The brain is located in the cranial cavity, the spinal cord is in the spinal canal. The nerves connected to the brain and exiting through openings in the bones of the skull are called cranial nerves. The nerves connected to the spinal cord and exiting the spinal canal through the intervertebral foramina are called spinal nerves.
The nervous system is formed by nervous tissue, and the structural unit nerve tissue is a nerve cell - a neuron.
Clusters of neuron cell bodies form the gray matter, and neuronal processes form the white matter. In the brain, gray matter is represented by the cerebral cortex and cerebellum) as well as various nuclei, in the spinal cord - by central gray matter. White matter forms associative, commissural and projection pathways.
In the peripheral N.s. neurons form nerve nodes - ganglia, and processes of nerve cells - nerve fibers. Nerve endings (receptors) convert irritation into a nerve impulse, which is sent to the central nervous system. The part of the peripheral nervous system through which the nerve impulse travels from the receptor is called afferent, centripetal, or sensory. From c.s.s. the nerve impulse follows the afferent, centrifugal, motor (or secretory) part and reaches the nerve ending (effector) in contact with the executive organ.
The nervous system is also divided into somatic and autonomic (vegetative).
To somatic N.s. include those parts that innervate the organs of the musculoskeletal system and the skin. The autonomous divisions include the divisions that innervate the internal organs. Both in the somatic part of the nervous system and in the autonomic part there are nerve nodes (ganglia).
Somatic ganglia are afferent spinal ganglia or ganglia of cranial nerves. One process extends from the cell body of the neurons that make them up, which then divides into two. The peripheral process reaches the receptor, and the central one reaches the sensitive nuclei in the central nervous system. The spinal nodes (31 pairs) look like thickenings of the dorsal roots of the spinal nerves. Of the sensory ganglia of the cranial nerves, the largest is the trigeminal ganglion (about 1 cm in diameter), and the smallest (less than 1 mm) is the inferior ganglion of the glossopharyngeal nerve.
Autonomic (effector) nodes contain multipolar neurons.
The dendrites of these cells do not leave the ganglion, and the axons reach the innervating organ. In accordance with the division of the autonomic nervous system into sympathetic and parasympathetic, the autonomic nodes are also divided into sympathetic and parasympathetic. The ciliary, pterygopalatine, auricular, sublingual and submandibular nodes are topographically connected with the three branches of the trigeminal nerve, and the axons of their neurons are part of the corresponding branches of the ophthalmic, maxillary and mandibular nerves.
Parasympathetic nodes are present in the walls of hollow internal organs and are located along the blood vessels in the thickness of the parenchymal organs. Intraorgan and periorgan parasympathetic nodes are part of the autonomic perivascular and intramural nerve plexuses. Sympathetic autonomic ganglia are located either along the spine, forming the right and left sympathetic trunks, or are part of the aortic prevertebral plexuses.
Contacts between neurons (interneuronal connections) are called synapses. There are synapses between the axon of one neuron and the body or dendrite of another, as well as synapses between the axons of two neurons. The processes of nerve cells (nerve fibers) are covered to varying degrees by myelin sheaths. Thin bundles of nerve fibers are surrounded by perineurium, and nerve roots, trunks and nerves are surrounded by epineurium.
The anterior branches of the cervical, lumbar and sacral spinal nerves form somatic plexuses. The anterior branches of the 1-4 spinal nerves are divided into bundles of nerve fibers, which are interconnected by arcuate loops and form the nerves and branches of the cervical plexus. Muscular branches innervate the deep muscles of the neck. Branches of 1, 2, sometimes 3 nerves connect into the cervical loop (deep cervical loop) and innervate the subhyoid group of muscles of the neck.
Cutaneous sensory nerves (greater auricular nerve, lesser occipital nerve, transverse cervical nerve and supraclavicular nerves) innervate the corresponding areas of the skin. The phrenic nerve (mixed - contains motor, sensory and sympathetic fibers) innervates the diaphragm, and the right one also partially innervates the liver.
The anterior branches of the 5-8 cervical nerves, sometimes part of the fibers of the 4th cervical and 1st thoracic nerves form the brachial plexus. In this case, after separation, three short nerve trunks are formed, passing in the interscalene space of the neck. Already in the supraclavicular region, the trunks are divided and in the axillary fossa around the artery of the same name they form medial, lateral and posterior bundles.
Thus, in the brachial plexus one can distinguish supraclavicular and subclavian parts. The short branches of the brachial plexus extending from the supraclavicular part innervate the muscles of the shoulder girdle, the skin of this area and the skin of the chest. From the subclavian part (from the bundles) the long branches of the brachial plexus begin - cutaneous and mixed nerves (musculocutaneous, median, radial and ulnar nerves), innervating the skin and muscles of the arm.
The lumbar plexus is formed by the connection of bundles of nerve fibers of the anterior branches 1-3, partially 12 thoracic and 4 lumbar nerves. In this plexus, as in the cervical one, there are no trunks, and the nerves are formed by connecting the named bundles of nerve fibers in the thickness of the lumbar (large and small) muscles. The branches of the lumbar plexus innervate the muscles and skin of the abdominal walls, partially the external genitalia, and the skin and muscles of the legs.
The anterior branches of the remaining part of the 4th lumbar nerve, 5th lumbar and sacral nerves form the sacral plexus. The anterior branches of the sacral nerves at the exit from the pelvic sacral foramina, fibers of the 4-5 lumbar nerves, united into the lumbosacral trunk, form a triangular neural plate on the anterior surface of the sacrum. The base of the triangle is directed to the sacral foramina, and the apex is directed towards the infrapiriform foramen and passes into the sciatic nerve (innervation of the muscles and skin of the leg), short muscle nerves innervate the muscles of the pelvic girdle, and cutaneous branches innervate the skin of the buttocks and thighs.
Autonomic plexuses, such as the superficial and deep cardiac plexuses, aortic - celiac (solar), superior and inferior mesenteric plexuses, are located in the adventitia of the aorta and its branches. In addition to these, there are plexuses on the walls of the pelvis - the upper and lower hypogastric plexuses, as well as intraorgan plexuses of hollow organs. The autonomic plexuses include ganglia and bundles of nerve fibers connected to each other.
PHYSIOLOGY
The basis for ideas about the functions of the nervous system is the neural theory, according to which the elementary structural unit of the N.S. recognized as a nerve cell. The most important property of a neuron is its ability to enter a state of excitation. The physiological properties of nerve cells, the mechanisms of their interactions and influences on various organs and tissues determine the main functions of the nervous system.
The nervous system functions on the principle of a reflex, which is externally manifested by a change in the activity of organs, tissues or the entire organism when receptors are irritated by agents of the external or internal environment. The structural basis of the reflex is the so-called reflex arc - receptors, afferent nerve fibers, central nervous system, efferent nerve fibers, effector.
Specific reflex reactions may include different quantity receptors, afferent and efferent neurons and complex processes interactions of excitations in the central nervous system At the same time, along the axon branches, without the participation of the neuron body, so-called axon reflexes can be carried out, which manifest themselves mainly in the autonomic nervous system and provide functional connections of internal organs and blood vessels to a certain extent regardless of the central nervous system.
Depending on the thickness and speed of excitation, all nerve fibers are divided into three large groups (A, B, C). Group A fibers are also divided into subgroups (a, b, g, and D). Subgroup A a includes thick myelinated nerve fibers (diameter 12-22 µm), conducting excitation at a speed of 70-160 m/s. They belong to the efferent motor fibers that originate from the motor neurons of the spinal cord and go to the skeletal muscles. Fibers of subgroups A b, A g and A D have a smaller diameter and a lower excitation speed. They are mainly afferent, conducting excitations from tactile, temperature and pain receptors.
Group B nerve fibers belong to thin myelinated fibers (diameter 1-3 µm), having an excitation velocity of 3-14 m/s and belonging to the preganglionic fibers of the autonomic nervous system. Thin unmyelinated nerve fibers of group C have a diameter of no more than 2 microns and an excitation speed of 1-2 m/s. This group includes postganglionic fibers of the sympathetic nervous system, as well as afferent fibers from some pain, cold, heat and pressure receptors.
Nerve fibers of all groups are characterized by general patterns of excitation. Normal conduction of excitation along a nerve fiber is possible only if its anatomical and physiological integrity ensures the safety of the mechanisms of excitation. All nerve fibers in the nerve trunk conduct excitations isolated from each other in any direction, but due to the presence of synapses with one-way conduction, excitation always propagates in one direction - from the neuron body along the axon to the effector.
The main functions of the nervous system are determined by the neurophysiological mechanisms of interneuronal interactions. The nature of the morphological connections between neurons and their functional relationships allow us to identify several common mechanisms. The presence of a widely branched dendritic tree in each neuron allows the cell to perceive a large number of excitations not only from various afferent structures, but also from various regions and nuclei of the brain and spinal cord.
The arrival of numerous heterogeneous excitations to an individual neuron is the basis of the convergence mechanism. There are several types of convergence of excitations on a neuron. The most studied and widely represented in the central scientific research center. multisensory convergence, which is characterized by the meeting and interaction on a neuron of two or more heterogeneous or heterotopic afferent excitations of different sensory modalities (visual, auditory, tactile, temperature).
Multisensory convergence is especially clearly manifested in the pontomesencephalic reticular formation, on the neurons of which excitations that arise from somatic, visceral, auditory, visual, vestibular, cortical and cerebellar stimulation interact. Convergence also occurs in the nonspecific nuclei of the thalamus, the median center, the caudate nucleus, the hippocampus and the structures of the limbic system.
In the cerebral cortex, along with numerous effects of multisensory convergence, other types of convergence of heterogeneous excitations to one neuron have been established. During the formation of a conditioned reflex, sensory-biological convergence is observed, manifested by the fact that excitations of the sensory (with a conditioned stimulus) and biological modality (with an unconditioned stimulus) converge to one cortical neuron.
Ascending to the cerebral cortex from subcortical structures, excitations specific in biological modality (painful, food, sexual, orientation-exploratory) can arrive at individual cortical neurons, manifesting themselves in the effects of multibiological convergence. The convergence of specific afferent excitations and excitations spreading along collaterals from efferent axons is called afferent-efferent.
The result of the interaction of converging excitations on a neuron can be the phenomena of propagation, facilitation, inhibition and occlusion. Prototyaniye consists in reducing the time of synaptic delay in the transmission of excitation due to the temporary summation of impulses following along the axon. The relief effect manifests itself when a series of excitation impulses causes a state of subthreshold excitation in the synaptic field of a neuron, which in itself is not yet sufficient for the appearance of an action potential on the postsynaptic membrane.
Only if there is a subsequent impulse passing along some other axons and reaching the same synaptic field can excitation occur in the neuron. In the case of simultaneous arrival of various afferent excitations to the synaptic fields of several neurons, a decrease in the total number of excited cells in the central nervous system is possible. (occlusion), which is manifested by a decrease in functional changes in the effector organ.
Electron microscopic studies of the synaptic organization of the central nervous system. also showed that a single large afferent ending contacts a large number dendrites of individual neurons. Such an ultrastructural organization can serve as the basis for a wide divergence of the excitation impulse, leading to the irradiation of excitations in the central nervous system. Irradiation can be directed (when excitation covers a certain group of neurons) and diffuse.
The combination of synaptic inputs from many neighboring cells on one neuron creates conditions for the multiplication of excitation impulses on the axon. In a network of neurons with cyclic closed connections (neural trap), a long-term, non-damping circulation of excitation occurs (prolonged excitation). Such functional connections can ensure long-term operation of effector neurons with a small number of those arriving in the central nervous system. afferent impulses.
Electrophysiological studies indicate the presence of a constant flow of excitation impulses from the central nervous system. to effectors. Such impulses indicate some constant tonic excitation of the structures of the nervous system. The tone of the nervous system is ensured not only by afferent impulses coming from peripheral receptors, but also by humoral influences (hormones, metabolites, biologically active substances).
Along with the mechanisms of excitation of nerve cells in the nervous system, there are mechanisms of inhibition, which are manifested by the cessation or decrease in the activity of neurons and individual organs. Unlike excitation, inhibition is a consequence of the interaction of two or more excitations. The nervous system has specialized inhibitory neurons that, when excited, suppress the activity of other nerve cells. The inhibitory effect of neurons is carried out by creating a short-term hyperpolarization of the postsynaptic membrane, called the inhibitory postsynaptic potential. Hyperpolarization appears when the postsynaptic membrane is exposed to inhibitory mediators such as g-aminobutyric acid, glycine, etc.
An important role in the activity of the nervous system is played by the mechanism of dominance of excitation that occurs in various structures of the brain and spinal cord. Neurons covered by dominant excitation are characterized by long-term increased excitability and an increase in the efficiency of temporal and spatial interneuronal interaction. Dominant arousal may underlie the formation of a purposeful behavioral act in animals and humans.
The nervous system has plasticity, i.e. the ability to rearrange its functional effects on an organ depending on the changed needs of the body. Such a restructuring is possible in case of damage to various parts of the brain or in cases where it is necessary to compensate for function in the periphery. The determining factor in the restructuring of processes in N.S. is a change in the quality of the flow of afferent impulses from the periphery, which signal the results of restructuring in the functioning of the organ under the influence of the nervous system.
One of the main functions of the nervous system is to regulate the activity of individual organs and tissues, carried out by its autonomic and somatic departments. The regulation of the body's autonomic functions is ultimately aimed at maintaining the constancy of its internal environment or homeostasis. The specific apparatus for ensuring homeostasis is functional systems body. Functional systems selectively combine various structures of the nervous system, which, in interaction with the endocrine glands, provide neurohumoral regulation of function.
Such brain structures are called centers of the nervous system. At the level of the lumbar spinal cord there are centers for defecation, urination, erection, ejaculation, as well as centers that regulate the tone of skeletal muscles lower limbs. At the level of the cervical spinal cord there is a center that regulates the work of the internal and external muscles of the eye, and some centers of the autonomic nervous system that regulate the activity of the heart and the tone of the bronchi.
In the medulla oblongata there are such vital centers as the respiratory center and the vasomotor center. There are also centers for sucking, chewing, swallowing, salivation, as well as those that carry out defensive reactions - vomiting, sneezing, coughing, blinking. At the level of the midbrain there are centers for regulating the tone of skeletal muscles. The variety of tonic reactions carried out by these centers can be divided into static, determining the position of the body in space, and statokinetic, aimed at maintaining the balance of the body when it moves.
In structures related to the diencephalon, such as the hypothalamus, thalamus and limbic system, there are centers that carry out and regulate more general integrative functions of the body: feelings of hunger, satiety, thirst, maintaining a constant body temperature, some instincts, as well as simple motor acts.
The highest regulator of all body functions, establishing subtle adequate relationships between the body and the environment, is the cerebral cortex. Various areas of the cortex, where different types of somatic and visceral sensitivity are represented, are the final link of the analyzers. In the posterior central gyrus of the cerebral cortex, somatic and musculo-articular sensitivity are represented.
In the superior temporal gyrus, along the edge of the posterior third of the Sylvian fissure, the auditory region is located, next to it is the vestibular region. Visual stimuli are perceived by the corresponding zone of the cortex of the occipital lobe of the brain. The anterior central gyrus is the zone where motor excitation reaches the periphery to the muscles of various parts of the body. Within it, groups of neurons can be distinguished, the excitation of which causes contraction of strictly defined muscle groups.
The destruction of areas of the cortex, which are the place of representation of various functions, leads to their disruption. On this basis, they talk about the localization of a particular function in the cerebral cortex, considering individual zones to be the highest centers of these functions. A similar approach to understanding the localization of functions in the central structures underlies the topical diagnosis of N.S. diseases. At the same time, the function is always localized dynamically depending on the complexity and nature of the reactions of the whole organism.
Higher forms of activity of the nervous system are associated primarily with the formation of goal-directed behavior, which includes the mechanisms of learning and memory (see Higher nervous activity). The central nervous system, especially such brain structures as the reticular formation and the thalamus, forms the state of sleep and wakefulness of a person. Limbic formations of the brain are the structural basis for the occurrence emotional states. Mechanisms of the nervous system - the basis mental activity a person, enriched by the development of speech, on the basis of which a person develops abstract thinking.
All formations of the nervous system have a high level of metabolism, which is reflected in the high rate of oxygen consumption, for example, neurons of the brain consume oxygen at a rate of 260-1080 µmol/h per 1 g, and glial cells - 50-200 µmol/h per 1 g The main energy supplier for N.S. is glucose. Glucose utilization in the brain occurs at a rate of 5.4 mg/min per 100 g. During metabolic processes in neurons, high-energy phosphates (ATP) and creatine phosphate are formed, which are involved in the operation of the membrane sodium pump.
In neurons, an intensive exchange of amino acids also occurs, in which the most important role belongs to glutamic and closely related g-aminobutyric acids. Free amino acids enter the nervous system from the bloodstream and are a source for the synthesis of proteins and biologically active compounds. Protein biosynthesis in neurons is several times higher than in neuroglia. All structures of the nervous system also have active systems for the synthesis and hydrolysis of all classes of lipids, the most numerous group being phospholipids.
RESEARCH METHODS
Methods for studying the state of the structures and functions of the nervous system. Computerization of medical and, in particular, neurological research has significantly expanded the possibilities for diagnosing diseases of the nervous system, primarily associated with focal damage to the structures of the central nervous system. and peripheral nervous system (tumors, abscesses of the brain and spinal cord, strokes, atrophy and developmental abnormalities of the nervous system, etc.), as well as those caused by hereditary metabolic disorders (amino acids, lipids, carbohydrates, metals, vitamins, etc.).
At the same time, the most effective remain clinical methods of neurological and neuropsychological examination of the patient, which are based on communication between the doctor and the patient, which has great value in the diagnosis of nervous system pathology and adequate selection of individually effective therapy. It is clinical studies that make it possible to determine the minimum range of necessary additional techniques that provide correct positioning topical and nosological diagnosis.
PATHOLOGY
The nervous system is the most integrated system of the body, representing both structurally and functionally a single whole. In this regard, even its local lesions, as a rule, have an impact on functional state not only those adjacent to the source, but also structures very distant from it. Defeat N.s. is also accompanied by various dysfunctions of internal organs due to the loss of its normal regulatory influences in pathology of the nervous system.
At the same time, the nervous system, protected by the blood-brain barrier and having relative immunological independence, is not always involved in pathological processes developing in the internal organs and systems of the body. Lesions of various parts and integrative levels of the central, peripheral and autonomic nervous system can be caused by many reasons, the main of which are vascular disorders, infections and intoxications, tumors, injuries, and exposure to various physical factors.
A large group consists of hereditary and congenital diseases of the nervous system, including those associated with the unfavorable course of the prenatal, intranatal and early postnatal periods of child development. as well as with hereditary metabolic disorders of amino acids, carbohydrates, lipids, vitamins, metals, etc.
The nature of the damage to the nervous system is clinically recognized by disturbances in movement, sensitivity, and autonomic functions. Neurological symptoms may be focal, i.e. associated with a specific lesion, and cerebral - dependent on changes in the function of the entire brain as a whole. Thus, when the pyramidal system is damaged, central paralysis and paresis are observed with a spastic increase in muscle tone and the appearance of pathological reflexes and automatisms.
Damage to the subcortical nodes belonging to the extrapyramidal system is manifested by motor disorders associated with the appearance of violent movements - hyperkinesis or, on the contrary, with the development of general muscle rigidity and a general impoverishment of movements. When the cerebellum and its connections are damaged, coordination of movements is impaired, and ataxia occurs at rest or during movement. Motor disturbances can also be observed in the case of a violation of praxis - apraxia, which is characterized by a violation of the general pattern of performing a particular motor act and a violation of voluntary movements despite the absence of paresis, ataxia or hyperkinesis.
Sensitivity disorders, depending on the affected conduction systems and centers, may concern disturbances in the tactile sense, pain and temperature perception, as well as proprioception of muscles and tendon-ligamentous apparatus. A weakening of sensitivity is accompanied by the appearance of anesthesia or hypoesthesia, and an increase in sensitivity is accompanied by hyperesthesia. A special group of pathologies consists of pain syndromes, as well as perversions of sensitivity.
Autonomic disorders include disorders of the functions of internal organs, the endocrine system, blood vessels, thermoregulation, and metabolism. In addition to apraxia, disorders of higher mental functions are accompanied by disorders of gnosis (visual, auditory, gustatory and other forms of agnosia), as well as speech (for example, motor and sensory aphasia). General cerebral disorders include disturbances of consciousness, headache, dizziness, and vomiting. Mental disorders with disorders of intelligence, thinking, memory, behavior and emotions require special clinical assessment.
Nervous system injuries include traumatic brain injury, spinal cord injury, and peripheral nervous system injury. In the acute period, patients with mild traumatic brain and spinal injuries (concussions of the brain and spinal cord), as well as mild contusions, do not require surgical treatment and are under the supervision of a neurologist (optimally in a hospital setting). In the presence of severe contusion, parenchymal and intrathecal hemorrhages with compression of the structures of the central nervous system. urgent surgical care is required.
In the long-term period of injuries to the central nervous system. syndromes of encephalopathy, traumatic epilepsy, cerebrasthenia, autonomic-visceral instability, myelopathy, leptomeningitis, etc. are observed. In connection with the development of microsurgical technology and modern electroneuromyographic methods for diagnosing nerve injuries, the principles of treatment and their course have changed significantly, and therefore increased frequency of full functional recovery after complete rupture of the nerve trunk.
Along with this, significant shifts in the structure of morbidity occur within each of these groups: the nature of neuroinfections changes, the role of viruses increases, incl. previously relatively pathogenic, the nature and structure of vascular diseases change, environmental factors influence the nature of intoxications, diseases of the development of the nervous system. This is due to environmental pollution, changes in the nutritional pattern of the population, as well as significant advances in diagnosis and treatment achieved by medicine over the past decades.
Functional diseases of the nervous system are divided into general neuroses (neurasthenia, hysteria, psychasthenia) and their local forms: motor (functional hyperkinesis, stuttering, etc.) and vegetative, as well as neurosis-like conditions or neurosis syndromes. Neurosis as a consequence of neuropsychic overstrain of microsocial conflicts is characterized by transient, mildly expressed disorders in the sphere of the psyche, emotions and behavior in the absence of organic symptoms of damage to the nervous system.
Vascular diseases account for up to 20% of all neurological diseases. These include chronic cerebral circulatory failure, acute circulatory disorders in the brain and spinal cord in the form of hemorrhagic and ischemic strokes, vascular crises, transient circulatory disorders in the central nervous system, intrathecal hemorrhages (epi- and subdural, subarachnoid), hemorrhages in ventricles of the brain, etc.
The origin of vascular diseases of the nervous system is associated with atherosclerosis, hypertension, aneurysms of the vessels of the brain and spinal cord, heart pathology, infectious diseases, intoxications, etc. The development of acute cerebrovascular accidents is caused mainly by progressive chronic cerebral circulatory failure, against which the direct pathogenetic mechanisms are significant fluctuations in blood pressure, heart rhythm disturbances, vasomotor disorders (spasms, stasis), changes in the rheological properties of blood, damage to the walls of blood vessels, incl. their congenital structural inferiority in malformations.
Neurological manifestations of vascular diseases can be general cerebral (in the initial stages of chronic cerebrovascular insufficiency, cerebral vascular crises) and focal (in acute cerebrovascular accidents - strokes, transient cerebral ischemia with symptoms of prolapse caused by destruction or ischemia of a particular area of the central nervous system. With.). Paralysis and paresis, ataxia, hyperkinesis, disorders of higher mental functions with disorders of gnosis, praxis and speech occur; with damage to the brain stem - alternating syndromes, dizziness, vomiting, nystagmus, respiratory and cardiac rhythm disorders; in case of damage to the spinal cord - symptoms associated with the level of damage and its prevalence. Analysis of clinical manifestations allows, as a rule, to determine the location of the lesion and its nature with fairly high accuracy.
The clinical picture depends on the type of pathogen and its pathogenicity, neurotropism to certain structures of the nervous system, and the form of the disease. General cerebral and meningeal symptoms are observed, which are usually detected against the background of general infectious manifestations (hyperthermia, intoxication). Focal symptoms make it possible not only to determine the topic of the predominant lesion, but often also to differentiate individual forms of neuroinfections. The etiology of the disease is established using special virological, bacteriological and serological studies of blood, cerebrospinal fluid, saliva, and tear fluid.
A special group of infectious lesions of the nervous system consists of the so-called slow neuroinfections, which include multiple sclerosis, Creutzfeldt-Jakob disease, amyotrophic lateral sclerosis, etc. With these diseases, there is a progressive increase in neurological symptoms, sometimes a remitting course, and therefore for a long time they were classified as chronic progressive diseases of the nervous system.
The clinical picture is characterized by a relative systemic involvement of structures of the nervous system, which allows them to be differentiated on the basis of a neurological examination; at the same time, as the process progresses, new functional systems can be involved, leading to increasing disability of the patient, loss of personal characteristics, and in some cases (with amyotrophic lateral sclerosis) and death due to damage to the vital parts of the central nervous system.
Hereditary degenerative diseases of the nervous system can be inherited in an autosomal dominant, autosomal recessive and sex-linked manner. The relatively pronounced systemic nature of damage to the nervous system in these diseases allows them to be divided into groups with predominant damage to the pyramidal system, subcortical formations, the cerebellum and its connections, and neuromuscular diseases. Progress wedge, genetics makes it possible to establish in certain hereditary diseases of the nervous system the fine molecular links of pathogenesis and even the primary biochemical defect.
The variety of wedges, forms of hereditary diseases of the nervous system, clinical polymorphism, the presence of transitional variants make their identification difficult, and therefore data banks, data registers with elements of machine diagnostics of hereditary diseases of the nervous system are created according to the complex of obligate and optional clinical, neurophysiological and biochemical signs of a particular disease. To genetic lesions N.s. These include chromosomal abnormalities, of which the most common are Down disease, Shereshevsky-Turner syndrome, Klinefelter syndrome, etc. The hereditary nature of a number of chronic progressive degenerative diseases of the nervous system (for example, myasthenia gravis, syringomyelia) has not been established.
Toxic lesions
A large group of toxic lesions of the nervous system consists of diseases associated with exogenous intoxications (methyl alcohol, potent drugs, industrial poisons, etc.), endogenous intoxications (with pathologies of the liver, kidneys, pancreas, gastrointestinal tract, etc.) , avitaminosis and others deficiency states, metabolic disorders due to porphyria, galactosemia, etc. Intoxication affects the cerebral cortex, subcortical nodes, cerebellum, but most often the structures of the peripheral nervous system (toxic polyneuropathy, encephalopathy, myelopathy).
Diseases of the peripheral nervous system are the most common and account for about 40-45% of neurological diseases. These include radiculitis, plexitis, neuritis and neuralgia, polyneuritis. True inflammation relatively rarely underlies damage to nerves, roots, and plexuses. Dystrophic changes usually predominate due to compression, microtrauma, etc. In this regard, in clinical practice the term “polyneuropathies” (hereditary, toxic, dysmetabolic, vascular, etc.) is more often used. Nerve lesions are accompanied by paresis of the muscles they innervate, impaired sensitivity and vegetative-trophic disorders in the innervation zone.
Diseases of the autonomic nervous system can be distinguished conditionally, because Autonomic disorders accompany, to one degree or another, almost all diseases of the nervous system. At the same time, there are hypothalamic syndromes, angiotrophoneurosis (which includes Raynaud's disease), vegetative ganglionitis, truncitis, solaritis. Attention to the pathology of vegetative N.s. increases in connection with the assessment of the role of its dysfunction in the origin and course of a number of somatic diseases (a special scientific direction, studying the problems of vegetative-visceral relationships - neurosomatic).
Diseases of the nervous system in childhood have features of both etiology and pathogenesis, as well as clinical manifestations. Factors of various origins that influence the growing and constantly functionally improving nervous system of a child, especially in the early stages of ontogenesis, determine the occurrence of clinically similar symptom complexes, the nature of which depends not so much on the etiological factor, but on the stage of brain development at which it had its effect .
Therefore, a large group of conditions of different origins are united under common names - “consequences of perinatal lesions of the c.n. pp.,” “cerebral palsy,” etc. The “perinatal” factor, in addition to direct damage to the brain, disrupts the program of its development. There is a lag in the development of basic motor, perceptual and intellectual functions, which aggravates the initially occurring defect. At the same time, the child’s brain is distinguished by extremely high plasticity and rich compensatory capabilities, and therefore a structural defect of the nervous system that arose pre- or intranatally can be completely compensated due to the plasticity of the intact parts.
TREATMENT
In the treatment of diseases of the nervous system, agents are used that correct microcirculation and metabolism in the nervous tissue, vitamins, biogenic stimulants, and nootropic agents. In recent years, agents that regulate immunological processes in the central nervous system have been introduced into clinical practice. (corticosteroids, cytostatics, levamisole, tactivin, etc.), as well as those affecting various ergic systems of the brain (transmitter and neuropeptide drugs). Antihypoxic and antioxidant therapy, complexones, correctors of membrane-destructive processes and the functioning of membrane ion channels are successfully used.
Great success has been achieved in the treatment of vascular diseases of the brain, early stages of chronic cerebral circulatory failure, some hereditary degenerative diseases of the nervous and neuromuscular systems (parkinsonism, torsion dystonia, hepatocerebral dystrophy, myasthenia gravis, myopathy).
The scope of use of reflexology methods in neurology is expanding. In pediatric neurology, certain successes have been achieved in the rehabilitation therapy of children with consequences of perinatal damage to the central nervous system. and cerebral palsy. The role of neurosurgical treatment of vascular lesions of the nervous system, hydrocephalus, stereotactic methods for parkinsonism, hyperkinesis, and surgical treatment of discogenic radiculitis is increasing.
Prevention is based on early diagnosis and active treatment of the initial stages of neurological diseases, prevention of unfavorable pregnancy and birth injuries to the child, and general health measures. Tumors of the brain and spinal cord are divided into primary and secondary, or metastatic.
Nervous system (sustema nervosum) is a complex of anatomical structures that ensure the individual adaptation of the body to the external environment and the regulation of the activity of individual organs and tissues.
Only a biological system can exist that is capable of acting in accordance with external conditions in close connection with the capabilities of the organism itself. It is this single goal - establishing behavior and state of the body that is adequate to the environment - are subordinated to the functions of individual systems and organs at each moment of time. In this regard, the biological system acts as a single whole.
The nervous system, together with the endocrine glands, is the main integrating and coordinating apparatus, which, on the one hand, ensures the integrity of the body, and on the other, its behavior adequate to the external environment.
The nervous system includes
the brain and spinal cord, as well as nerves, ganglia, plexuses, etc. All these formations are predominantly built from nervous tissue, which
- capable get excited under the influence of irritation from the environment internal or external to the body and
- excite in the form of a nerve impulse to various nerve centers for analysis, and then
- transmit the “order” developed at the center to the executive bodies to perform a response of the body in the form of movement (movement in space) or changes in the function of internal organs.
Excited e tion
-
active physiological process
, with which some types of cells respond to external influences. The ability of cells to generate excitation is called excitability. Excitable cells include nerve, muscle and glandular cells.
All other cells have only irritability, i.e.
the ability to change their metabolic processes when exposed to any factors
(irritants).
In excitable tissues, especially nervous tissues, excitation can spread along the nerve fiber and is a carrier of information about the properties of the stimulus
. In muscle and glandular cells, excitation is a factor that triggers their specific activity - contraction, secretion.
Braking e tion
in the central nervous system - active physiological process
, the result of which is a delay in the excitation of the nerve cell.
Together with excitation, inhibition forms the basis of the integrative activity of the nervous system and ensures the coordination of all functions of the body.
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The human nervous system is classified According to the method of transmitting information as: By area of localization as: By functional affiliation as: |
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The anatomical and functional unit of the nervous system is the nerve cell - neuron. Neurons have processes with which they connect with each other and with innervated formations (muscle fibers, blood vessels, glands). The processes of the nerve cell are unequal in functionally: some of them conduct stimulation to the neuron body - This dendrites, and only one shoot - axon - from the nerve cell body to other neurons or organs .
The processes of neurons are surrounded by membranes and combined into bundles, which form nerves. The membranes isolate the processes of different neurons from each other and contribute to the conduction of excitation. The sheathed processes of nerve cells are called. The number of nerve fibers in different nerves ranges from 102 to 105. Most nerves contain processes of both sensory and motor neurons. Interneurons are predominantly located in the spinal cord and brain, their processes form the pathways of the central nervous system.
Most nerves in the human body mixed, that is, they contain both sensory and motor nerve fibers. That is why, when nerves are damaged, sensory disorders are almost always combined with motor disorders.
Irritation is perceived by the nervous system through the sense organs (eye, ear, organs of smell and taste) and special sensitive nerve endings - receptors located in the skin, internal organs, blood vessels, skeletal muscles and joints.
The functioning of the nervous system is based on neurohumoral regulation And reflex regulation .
Neurohumoral regulation (Greek neuron nerve + lat. humor fluid) - regulating and coordinating influence of the nervous system and those contained in the blood, lymph and tissue fluid biologically active substances on the vital processes of the human and animal body. Numerous specific and nonspecific metabolic products (metabolites) are involved in the neurohumoral regulation of functions. N.r.f. is important for maintaining the relative constancy of the composition and properties of the internal environment of the body, as well as for adapting the body to changing conditions of existence. Interacting with the somatic (animal) nervous system and the endocrine system, the neurohumoral regulatory function ensures the maintenance of constant homeostasis And adaptation in changing environmental conditions.
For a long time, nervous regulation was actively opposed to humoral regulation. Modern physiology has completely rejected the opposition of individual types of regulation (for example, reflex - humoral-hormonal or other). At the early stages of the evolutionary development of animals, the nervous system was in its infancy. Communication between individual cells or organs in such organisms was carried out using various chemical substances , secreted by working cells or organs (i.e., was humoral in nature). As the nervous system improved, humoral regulation gradually came under the controlling influence of a more advanced nervous system. At the same time, many transmitters of nervous excitation (acetylcholine, norepinephrine, gemma-aminobutyric acid, serotonin, etc.), having fulfilled their main role - the role mediators and, having avoided enzymatic inactivation or reuptake by nerve endings, enter the blood, carrying out a distant (non-mediator) effect. In this case, biologically active substances penetrate through histohematic barriers into organs and tissues, direct and regulate their vital functions.
Reflex regulation
Reflex(lat. reflexus turned back, reflected) is the body’s response to external or internal irritation with the participation of the nervous system, ensuring the occurrence, change or cessation functional activity
organs, tissues or the whole organism, carried out with the participation of the central nervous system in response to irritation of the body’s receptors.
The reflex pathway in the body is a chain of sequentially interconnected neurons
, transmitting irritation from the receptor to the spinal cord or brain, and from there to the working organ (muscle, gland). It is called reflex arc
.
Each neuron in the reflex arc performs its own function. There are three types of neurons:
irritable- sensitive ( afferent) neuron,
conveying irritation to the working organ - motor ( efferent) neuron,
connecting sensory and motor neurons - intercalary ( association neuron). In this case, excitation is always carried out in one direction: from sensory to motor neuron.
Reflex is the elementary unit of nervous action . Under natural conditions, reflexes are not carried out in isolation, but are combined (integrated) into complex reflex acts, having a certain biological orientation. The biological significance of reflex mechanisms lies in the regulation of the work of organs and the coordination of their functional interaction in order to ensure the constancy of the internal environment of the body, maintaining its integrity and the ability to adapt to constantly changing environmental conditions.
Reflexes are grouped into different groups
depending on the leading feature taken as the basis for their division. A fairly common characteristic of reflexes along individual links of the reflex arc. By receptor location reflexes are divided into extero-, intero- and proprioceptive, according to the location of the central link- spinal, bulbar, mesencephalic, cerebellar, diencephalic, cortical; by localization of the efferent part- somatic and vegetative; according to the reaction caused - swallowing, blinking, coughing, etc.
According to the classification of I.I. Pavlov, all reflexes are divided into innate, or unconditional(they are species-specific and relatively constant), and individually acquired, or conditional reflexes (are changeable and temporary in nature and are developed in the process of interaction of the body with the environment).
Unconditioned reflexes are divided into simple (food, defensive, sexual, visceral, tendon) and complex reflexes (instincts, emotions). Some researchers also classify indicative (orientative-exploratory) reflexes as unconditioned reflexes. The instinctive activity of animals (instincts) includes several stages of animal behavior, and the individual stages of its implementation are sequentially related to each other according to the type chain reflex.
Based on the provisions of I.P. Pavlova about nerve center As a morphofunctional set of nerve formations located in various parts of the central nervous system, the concept of the structural and functional architecture of the unconditioned reflex was developed. The central part of the arc B.r. does not pass through any one part of the central nervous system, but is multi-storey and multi-branched. Each branch passes through an important part of the nervous system: the spinal cord, medulla oblongata, midbrain, and cerebral cortex. The higher branch, in the form of the cortical representation of one or another unconditioned reflex, serves as the basis for the formation of conditioned reflexes.
Makes up the so-called
lower nervous activity
animals.
Evolutionarily more primitive species of animals are characterized by simple unconditioned reflexes and instincts, for example, in animals in which the role of acquired, individually developed reactions is still relatively small and innate, albeit complex forms of behavior predominate, dominance of tendon and labyrinthine reflexes is observed. With the complication of the structural organization of the c.s.s. and the progressive development of the cerebral cortex, complex unconditioned reflexes and, in particular, emotions acquire a significant role. 
Conditioned reflexes
- body reactions (reflexes), produced under certain conditions
during the life of a person or animal on the basis of innate unconditioned reflexes. Unlike unconditioned reflexes, conditioned reflexes have the ability to quickly form
(when the body needs it in a given situation) and to the same rapid fading
(when the need for them disappears).
Conditioned reflex excitation occurs when any indifferent stimulus(lat. indifferens - indifferent) reinforced by unconditional. Thanks to temporary connections of varying complexity, previously indifferent stimuli preceding a particular activity become a signal (condition) of this activity. Having acquired a signal value, the conditioned stimulus leads to the emergence of a signal in the central nervous system. excitation that outstrips the activity of brain structures that ensure the formation of future behavior. Such anticipatory excitation not only ensures a biologically expedient adaptation of the organism to the environment, but also underlies the active influence on this environment.
Thus, the conditioned reflex is one of the main types of adaptive activity of the body, carried out by the higher departments of the central nervous system. by the formation of temporary connections between signal stimulation and unconditioned
(innate) reaction of the body.
The classification of conditioned reflexes may be based on the nature of the response (motor, secretory, etc.); method of formation (UR of the first, second and other orders, associative, imitation, etc.), biological significance (nutritional, defensive, orientation-research, etc.).
A set of unconditioned reflexes
amounts to higher nervous activity
.
Higher nervous activity - integrative activity of the higher parts of the central nervous system (cerebral cortex and subcortical centers), ensuring the most perfect adaptation of animals and humans to the environment.
As a result of long evolutionary development, the nervous system turned out to be represented by two sections. They are clearly different in appearance, but structurally and functionally they form a single whole. This central nervous system
in the form of the brain and spinal cord and peripheral nervous system
, represented by nerves, nerve plexuses and nodes.
The central nervous system (systema nervosum centrale) is represented by head And spinal cord. In their thickness, areas of gray color (gray matter) are clearly visible, this is the appearance of clusters of neuron bodies, and white matter, formed by the processes of nerve cells, through which they establish connections with each other. The number of neurons and the degree of their concentration are much higher in the upper section, which as a result takes on the appearance of a three-dimensional brain.
Spinal cord located in the spinal canal from the first cervical to the second lumbar vertebra. Externally, the spinal cord resembles a cord cylindrical. 31 pairs of spinal nerves depart from the spinal cord, which leave the spinal canal through the corresponding intervertebral foramina and branch symmetrically in the right and left halves of the body. The spinal cord is divided into cervical, thoracic, lumbar, sacral and coccygeal sections, respectively; among the spinal nerves, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1-3 coccygeal nerves are considered. The section of the spinal cord corresponding to a pair (right and left) of the spinal nerves is called segment of the spinal cord
.
Every spinal nerve
is formed as a result of the fusion of the anterior and posterior roots extending from the spinal cord. On the dorsal root there is a thickening - the spinal ganglion, where the bodies of sensory neurons are located. The processes of sensory neurons carry excitation from the receptors to the spinal cord.
The anterior roots of the spinal nerves are formed by processes of motor neurons, which transmit commands from the central nervous system to skeletal muscles and internal organs.
At the level of the spinal cord, reflex arcs close, providing the simplest reflex reactions, such as tendon reflexes (for example, the knee reflex), flexion reflexes when irritating pain receptors in the skin, muscles and internal organs. An example of a simple spinal reflex is the withdrawal of a hand when it touches a hot object. The reflex activity of the spinal cord is associated with maintaining posture, maintaining a stable body position when turning and tilting the head, alternating flexion and extension of paired limbs when walking, running, etc. In addition, the spinal cord plays an important role in regulating the activity of internal organs, in particular the intestines, bladder, and blood vessels.
Peripheral nervous system
Basically it is a connecting link between the central nervous system and organs. The nerves that make up the peripheral nervous system are not independent structures; they are formed by processes of motor neurons, the bodies of which are located in the brain and spinal cord, and processes of sensory neurons that carry information to the central nervous system. Thus, from the point of view of functions and structure, the division of the nervous system into central and peripheral is relative; the nervous system is one.
The nerves that make up the peripheral nervous system are formed motor, sensitive
And vegetative fibers
.
Motor fibers are long processes (axons) of neurons, the bodies of which are located in the spinal cord and in parts of the brain, they follow to striated fibers of body muscles.
Sensitive fibers - processes of neurons of the same name, whose bodies are located in the form of clusters (sensitive nodes) inside the nerves in close proximity to the central nervous system, they carry information to the centers spinal and brain.
The peripheral nervous system is represented
:
a) 12 cranial nerves (on both sides), which provide brain control over the head and neck areas;
b) the 31st pair of spinal nerves, through which the spinal cord controls the torso, limbs, and organs of the thoracic and abdominal cavities.
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Schematic representation of the structure of the human autonomic nervous system and the organs innervated by it (shown in red sympathetic nervous system, blue - parasympathetic; connections between cortical and subcortical centers and spinal cord formations are indicated by a dotted line).
1
And 2
- cortical and subcortical centers; |
The nervous system is also divided into somatic and autonomic (autonomic).
TO somatic nervous system include those parts that innervate the organs of the musculoskeletal system and the skin (Greek sō ma, sō matos - body, “relating to the body”).
The autonomic nervous system (systema nervosum autonomicum; synonym: autonomic nervous system, involuntary nervous system, visceral nervous system) is a part of the nervous system that ensures the activity of internal organs, regulation of vascular tone, innervation of glands, trophic innervation of skeletal muscles, receptors and the nervous system itself.
Autonomic fibers emerge from the central nervous system and, subsequently leaving the main nerve trunks, through the system of vegetative nodes regulate the functioning of internal organs . Such relationships between the peripheral and central nervous systems indicate their functional and structural unity.
The autonomic nervous system has central and peripheral sections.
In the central department
There are suprasegmental (higher) and segmental (lower) vegetative centers.
Suprasegmental autonomic centers
concentrated in brain- in the cerebral cortex (mainly in the frontal and parietal lobes), hypothalamus, olfactory brain, subcortical structures (striatum), in the brain stem (reticular formation), cerebellum, etc.
Segmental autonomic centers
located and in the brain and spinal cord.
The autonomic centers of the brain are conventionally divided into midbrain and bulbar (autonomic nuclei of the oculomotor, facial, glossopharyngeal and vagus nerves), and the spinal cord into lumbosternal and sacral.
Motor centers innervation of non-striated (smooth) muscles of internal organs and vessels are located in precentral And frontal areas. There are also reception centers from internal organs and blood vessels, centers of sweating, nervous trophism, and metabolism. The centers of thermoregulation, salivation and lacrimation are concentrated in the striatum. The participation of the cerebellum in the regulation of such autonomic functions as the pupillary reflex and skin trophism has been established. The nuclei of the reticular formation constitute the suprasegmental centers of vital functions - respiratory, vasomotor, cardiac activity, swallowing, etc.
Peripheral department The autonomic nervous system is represented by nerves and nodes located near internal organs (extramural) or in their thickness (intramural).
The autonomic nodes are connected to each other by nerves, forming plexuses, for example pulmonary, cardiac, abdominal aortic plexus.
Sympathetic nervous system
(pars sympathica, Greek sympathēs - experiencing a similar feeling), part of the autonomic nervous system, including nerve cells of the thoracic and upper lumbar spinal cord and nerve cells of the border sympathetic trunk, solar plexus, mesenteric nodes, the processes of which innervate all organs.
The influence of the sympathetic nervous system on the central nervous system. is manifested by a change in its bioelectrical activity, as well as its conditioned and unconditioned reflex activity.
With increased tonesympathetic nervous system are intensifying heart contractions and their rhythm become more frequent, the speed of excitation through the heart muscle increases, blood vessels constrict, blood pressure increases, metabolism increases, blood glucose increases, bronchi and pupils dilate, the secretory activity of the adrenal medulla increases, the tone of the gastrointestinal tract decreases etc.
Parasympathetic nervous system
(pars parasympathica, Greek raga- - prefix meaning “retreat, deviation from something”, etc.) - part of the autonomic nervous system, represented by the oculomotor, facial, glossopharyngeal, vagus nerves and their nuclei, neurons of the lateral horns of the spinal cord at the level of the II-IV sacral segments, as well as associated ganglia, pre- and postganglionic fibers.
Increased tone parasympathetic nervous system
accompanied by decrease strength and frequency of heart contractions, slowing down the speed of excitation through the myocardium, reducing blood pressure, increased insulin secretion and decreased blood glucose concentration, increased secretory and motor activity of the gastrointestinal tract.
Many internal organs receive both sympathetic and parasympathetic innervation. The influence of these two departments is often antagonistic, but there are many examples where both departments act synergistic(so-called functional synergy).
In many organs having both sympathetic and parasympathetic innervation
, under physiological conditions the regulatory influences of the parasympathetic nerves predominate. These organs include the bladder and some exocrine glands (lacrimal, digestive, etc.).
There are also organs supplied only by sympathetic or only parasympathetic nerves
; These include almost all blood vessels, the spleen, smooth muscles of the eyes, some exocrine glands (sweat glands) and smooth muscles of the hair follicles.
The transmission pathways of adaptation-trophic influences are based on straight And indirect types of sympathetic innervation . There are tissues endowed with direct sympathetic innervation (cardiac muscle, uterus and other smooth muscle formations), but the bulk of tissues (skeletal muscles, glands) have indirect adrenergic innervation. In this case, the transmission of the adaptation-trophic influence occurs humorally: the mediator is transferred to the effector cells by the blood stream or reaches them by diffusion.
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. By outer surface The spinal cord contains white matter - a collection 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 Paths conduct excitation from the brain to 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 in humans high development, making up 80% of the brain mass. The phylogenetically more ancient part is the brain stem. The trunk includes the medulla oblongata, pons, midbrain and diencephalon. Numerous nuclei lie in the white matter of the trunk 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 the peripheral nerve ganglia located in 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 chemical and gas composition 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 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 in them general properties, 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 they are formed general concepts. 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 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 structure through which all human organs and life support systems function. This article will talk about the nervous system, its components, functioning and types.
central nervous system
The anatomical structure of the nervous system involves division into central and peripheral. What is the nervous system? This concept can be defined as the interaction of these two subsystems, since the central one is the brain and spinal cord, and the peripheral one is the spinal and cranial nerves and nerve ganglia extending from them to all parts of the body.
Thus, the central nervous system is connected to all parts of the body thanks to nerve fibers - neurons, from which neural chains are built. To understand what the central nervous system is and how it works, you need to imagine its location.
The spinal cord of an adult weighs about 30 grams. and is approximately 45 cm in length. It is located in the brain canal surrounded by the meninges, which act as shock absorbers. The volume of the spinal cord is the same along its entire length; there are thickenings only in the cervical and lumbar regions. This is where the nerve endings of the upper and lower extremities are formed. In total, the spinal cord has 5 sections: cervical, thoracic, lumbar, sacral and coccygeal.
The brain is located in the area of the skull, and is divided into the right hemisphere, which is responsible for the formation of imaginative thinking, and the left, responsible for abstract thinking. The brainstem and cerebellum are also distinguished.
It has been scientifically confirmed that the female brain is approximately 100 grams lighter than the male brain. The explanation for this may be that the male body is more physically developed than the female. At the same time, the brain begins to form in the womb, and reaches its real size only by the age of twenty.
Somatic nervous system
A conventional division of the nervous system into autonomic and somatic is accepted. Moreover, the somatic nervous system is sometimes called “animal”, i.e. characteristic of animals. This means that it is responsible for controlling a person’s skeletal muscle mass, his movement in space, his relationship with the environment, as well as the functioning of his senses.
Autonomic nervous system
Let's look at what the autonomic nervous system is. This is part of the general nervous system, responsible for the functioning of the heart muscle, blood vessels, and some types of glands. It is customary to divide the autonomic nervous system into two parts: sympathetic and parasympathetic. They complement each other.
Sympathetic nervous system
The sympathetic nervous system is responsible for processes that must mobilize the body's resources when stress or an extreme situation occurs. These are heart rate, changes in blood pressure, blood sugar levels, pupil dilation and bronchial function. This is the understanding of what the sympathetic nervous system is. The parasympathetic nervous system also acts in support of it. It regulates the functioning of the bladder, rectum, genitals, i.e. helps accumulate and restore the body's energy resources.
Parasympathetic nervous system
It is necessary to separately consider what the parasympathetic nervous system is. It lowers blood pressure, helps reduce heart rate, and regulates the functioning of the digestive system.
The control of the sympathetic and parasympathetic systems occurs thanks to special autonomic apparatuses located in the brain.
Prevention and prevention of diseases of the autonomic nervous system is necessary, because even changes in weather conditions, for example, extreme heat or frost, can be the cause. Symptoms may include redness or paleness of the face, increased heart rate, and increased sweating. Therefore, you need to avoid stressful situations, illnesses due to the weather, try to follow safety precautions at the workplace, maintain a healthy diet, and also undergo regular medical examinations and consult a doctor in a timely manner if you have concerns.
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.
