The human peripheral nervous system. Peripheral nervous system, its structure and functions. How is the diagnosis

(systerna nervosum periphericum)

a conditionally allocated part of the nervous system, the structures of which are located outside the brain and spinal cord. The peripheral nervous system includes 12 cranial nerves (Cranial nerves), their roots, sensory and autonomic ganglia located along the trunks and branches of these nerves (see Autonomic nervous system), as well as the anterior and posterior roots of the spinal cord and 31 spinal nerves ( see Nerves), sensory ganglia, nerve plexuses (see Cervical plexus, brachial plexus, lumbosacral plexus), peripheral nerve trunks of the trunk and extremities, right and left sympathetic trunks, ganglia and nerves. The conditionality of the anatomical separation of the central and peripheral nervous system is determined by the fact that the nerve fibers that make up are either axons of motor neurons located in the anterior horns of the spinal cord segment, or dendrites of sensitive neurons of the intervertebral ganglia (the axons of these cells are sent along the posterior roots to). Thus, the bodies of neurons are located in the central nervous system, and their processes are located in the peripheral (for motor cells), or, conversely, the processes of neurons located in the peripheral nervous system constitute the c.n.s. (for sensitive cells). Basic P. n. With. is to provide communication ts.n.s. with the environment and target organs. It is carried out either by conducting nerve impulses of extero-, proprio- and interoreceptors to the corresponding segmental and suprasegmental formations of the spinal cord and brain, or in the opposite direction - regulatory signals from the central nervous system. to the muscles that ensure the movement of the body in the surrounding space, to internal organs and systems. P.'s structures n. With. have their own vascular and innervation supply that supports the trophism of nerve fibers and ganglia; as well as its own liquor system in the form of capillary gaps along the nerves and plexuses. It is formed starting from the intervertebral ganglia (right in front of which, on the spinal roots, it ends in blind sacs with cerebrospinal fluid that bathes the central nervous system). Thus, both CSF systems (central and peripheral nervous systems) are separate and have a kind of barrier between them at the level of the intervertebral ganglia. In the peripheral nervous system, nerve trunks may contain motor fibers (anterior roots of the spinal cord, facial, abducens, trochlear, accessory and hypoglossal), sensory (posterior roots of the spinal cord, sensitive part of the trigeminal nerve, auditory nerve) or autonomic (sympathetic and parasympathetic systems) . But the main part of the upper trunks of the trunk and limbs is mixed (contains motor, sensory and autonomic fibers). The mixed nerves include intercostal nerves, trunks of the cervical, brachial and lumbosacral plexuses and the nerves of the upper (radial, median, ulnar, etc.) and lower (femoral, sciatic, tibial, deep peroneal, etc.) ) limbs. The ratio of motor, sensory and autonomic fibers in the trunks of mixed nerves can vary significantly. The largest number of autonomic fibers contain the median and tibial nerves, as well as the vagus nerve. Despite the external disunity of a separate nerve trunks P. n. N of page, between them there is a certain functional interrelation provided by nonspecific structures ts.n.s. This or that individual nerve trunk affects the functional state not only of the symmetrical nerve, but also of distant nerves on its own and opposite side of the body: in the experiment, the contralateral neuromuscular preparation increases, and in the clinic, with mononeuritis, the conduction indices along other nerve trunks increase. The specified functional interrelation to some extent (along with other factors) determines the characteristic for P. n. With. the multiplicity of lesions of its structures - polyneuritis and, polyganglionitis, etc.

P.'s defeats n. With. can be caused by a variety of factors: trauma, metabolic and vascular disorders, infections, intoxications (domestic, industrial and medicinal), vitamin deficiency and other deficient conditions. A large group of diseases P. n. With. make up hereditary polyneuropathies: neural Charcot - Marie - Tuta (see Amyotrophy), Roussy - Levi syndrome, hypertrophic polyneuropathy Dejerine - Sotta and Marie - Boveri, etc. In addition, a number of hereditary diseases of the c.n.s. is followed by P.'s defeat of n. S.: family Friedreich (see Ataxia), family Strumpell (see Paraplegia (Paraplegia)), ataxia-telangiectasia Louis-Bar, etc. Depending on the predominant localization of P.'s lesion n. With. distinguish Radiculitis, Plexites, ganglionites, Neuritis, as well as combined lesions - polyradiculoneuritis, polyneuritis (polyneuropathies). The most common cause of radiculitis is metabolic-dystrophic changes in the spine with osteochondrosis, herniated discs. Plexitis is more often caused by compression of the trunks of the cervical, brachial and lumbosacral plexuses by pathologically altered muscles, ligaments, vessels, the so-called cervical ribs and other formations, “for example, tumors, enlarged lymph nodes). The spinal ganglia are mainly affected by the herpes virus. A large group of compression lesions of P. n is described. N of page, connected with a prelum of its structures in fibrous, bone, muscular channels (Tunnel syndromes). defeats of P.'s structures of n. With. due to the involvement of motor, sensory and autonomic fibers that make up the nerve trunks (, paresis, muscle atrophy, disorders of superficial and deep sensitivity in the area of ​​impaired innervation in the form of pain, paresthesia, anesthesia, causalgia syndromes and phantom sensations, vegetative-vascular and trophic disorders more often in the distal extremities). A separate group consists of pain syndromes, which often occur in isolation, not accompanied by symptoms of loss of functions - neuralgia, plexalgia, radiculalgia. The most severe pain syndromes are observed with ganglionitis (sympathalgia), as well as injuries of the median and tibial nerves with the development of causalgia (causalgia).

At children's age a special form of pathology of P. of n. With. are the birth roots of the spinal cord (mainly at the level of the cervical, less often the lumbar segments), as well as the trunks of the brachial plexus with the development of birth traumatic paralysis of the arm, less often the leg. With a birth injury of the brachial plexus and its branches, Duchenne-Erb or Dejerine-Klumpke paralysis occurs (see Brachial plexus).

Tumors P. n. With. (neurinomas, neurofibromas, glomus) are relatively rare, but can occur at its various levels.

Diagnosis of lesions P. n. With. based primarily on the data of the clinical examination of the patient. Predominantly distal paralysis and paresis with impaired sensitivity, vegetative-vascular and trophic disorders in the zone of innervation of one or another nerve trunk are characteristic. With damage to the peripheral nerve trunks, a thermal imaging study has a certain diagnostic value, which reveals the so-called amputations in the denervation zone due to a violation of thermoregulation in it and a decrease in skin temperature. They also conduct electrodiagnostics and chronaximetry, but recently these methods are inferior to electromyography and electroneuromyography, the results of which are much more informative. Electromyography reveals characteristic denervation changes in the bioelectrical activity of paretic muscles in neural lesions. The study of the velocities of impulse conduction along the nerves allows you to determine the exact localization of the lesion of the nerve trunk by their decrease, as well as to identify the degree of involvement in the motor or sensory nerve fibers. For P.'s defeat n. With. a decrease in the amplitudes of the evoked potentials of the affected nerve and denervated muscles is also characteristic. To clarify the nature of the pathological process in polyneuropathies, nerve tumors, a biopsy of the skin nerves is used, followed by histological and histochemical examination. With clinically diagnosed tumors of the nerve trunks, computed tomography (CT) can be used, which is of particular importance in cases of tumors of the cranial nerves (for example, with acoustic neuroma). Computer allows you to establish the localization of the intervertebral disc, which is important for its subsequent prompt removal.

Treatment of diseases P. n. With. It is aimed at eliminating the action of the etiological factor, as well as at improving microcirculation and metabolic and trophic processes in the nervous system. Group B, potassium preparations and anabolic, anticholinesterase drugs and other neural conduction stimulants, nicotinic acid preparations, cavinton, trental, as well as drug metameric therapy are effective. Physiotherapeutic procedures are prescribed (, pulsed currents, electrical stimulation, diathermy and other thermal effects), physiotherapy exercises, sanatorium-and-spa. With tumors of the nerves, as well as with their injuries, according to indications, surgical treatment is performed. In recent years, kronasial has been developed containing a certain composition of gangliosides - receptors for neuronal membranes; its intramuscular application stimulates synaptogenesis and regeneration of nerve fibers.

Bibliographer.: Badalyan L.O. and Skvortsov I.A. Clinical electroneuromyography, M., 1986; Gusev E.I., Grechko V.E. and Buryag S. Nervous diseases, p. 379, M. 1988; Popelyansky Ya.Yu. Diseases of the peripheral nervous system, M., 1989, bibliogr.

1. Small medical encyclopedia. - M.: Medical Encyclopedia. 1991-96 2. First aid. - M.: Great Russian Encyclopedia. 1994 3. Encyclopedic dictionary of medical terms. - M.: Soviet Encyclopedia. - 1982-1984.

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The peripheral nervous system contains nerves, cranial nerve nodes and spinal ganglia located along their course. It connects with internal organs, skin and muscles Based on this connection, the peripheral nervous system is of two types: autonomic and somatic. The latter is formed by those nerves that connect the CNS to the muscles, skin, and tendons. To belong to those nerves that connect the central nervous system with the glands, blood vessels and internal organs.

Sensory and motor nerves make up the spinal nerves. Receptors are located on the skin, muscles, mucous membranes, internal organs, tendons. These formations are the beginning of sensitive fibers. They send signals that contain data about the state of the body and its environment to the central nervous system. On the motor fibers, on the contrary, the central nervous system sends signals to the vessels, internal organs, and muscles. Thus, it controls the body's response to certain stimuli perceived by receptors.

Connected to the brain. Thanks to them, the nasal cavity and mouth, the larynx, the mucous membrane of the eyes, and the skin of the face remain sensitive. They also provide a connection of the central nervous system with all the receptors of hearing, taste, sight and smell. These are somatic fibers, and vegetative ones control the functioning of the glands (both lacrimal and salivary), are also involved in the process of respiration, in the work of the heart and digestive organs.

The peripheral nervous system must very quickly deliver motor or sensory impulses to the central nervous system. This is essential to ensure fast communication between the brain, spinal cord and receptors.

Peripheral is subject to a considerable number of diseases. Their causes are very diverse: poisoning, trauma, circulatory or metabolic disorders, inflammation. Often there is a combination of several factors.

The classification of these diseases depends on which part of the peripheral nervous system is affected. If the endings of the spinal cord become inflamed, sciatica occurs, if the nerve plexuses are affected - pleurisy. More often, peripheral neuropathy is manifested by a complex of symptoms. So, if a part of the spinal cord suffers, plexitis, neuritis, and radiculitis appear. They are accompanied by pain in the direction of the nerve trunks, the sensitivity of the skin in this area decreases, muscle weakness appears, and they gradually atrophy. The manifestations are the same, only the localization of the lesion changes.

But if any of the cranial nerves is damaged, there is a violation of the perception of visual images, sound signals and smells, but there is no pain, loss of sensitivity. The peripheral nervous system has several departments, therefore, the treatment of diseases depends on the cause that caused them, and on which part of it is affected. After a thorough examination, the doctor prescribes medications, physiotherapy procedures. Depending on the severity of the disease, the patient is offered a stay in the hospital or Surgical intervention is used only in case of rupture of peripheral nerves resulting from trauma.

Prevention of diseases is the observance of safety precautions when working with poisons. Hypothermia should be avoided. Patients with diabetes mellitus, in order to prevent diabetic polyneuritis, should regularly visit a doctor and undergo a special preventive course. Smokers and alcoholics are especially prone to damage to this system.

The peripheral nervous system is a conditionally distinguished part of the nervous system, the structures of which are located outside the brain and spinal cord.

The nervous system is made up of cells neurons whose function is to process and disseminate information. Neurons communicate with each other through connections - synapses. One neuron transmits information to another through synapses using chemical carriers - mediators. Neurons are divided into 2 types: excitatory and inhibitory. The body of the neuron is surrounded by densely branching processes - dendrites, which are designed to receive information. The branch of a nerve cell that transmits nerve impulses is called axon. Its length in humans can reach 1 meter.

The peripheral nervous system is subdivided into autonomic nervous system responsible for the constancy of the internal environment of the body, and somatic nervous system, innervating (supplying nerves) muscles, skin, ligaments.

The composition of the peripheral nervous system (or the peripheral part of the nervous system) includes nerves extending from the brain - cranial nerves and from the spinal cord - spinal nerves, as well as nerve cells that have moved outside the central nervous system. Depending on what type of nerve fibers are predominantly part of the nerve, there are motor, sensory, mixed and autonomous (vegetative) nerves.

Nerves appear on the surface of the brain as motor or sensory roots. In this case, the motor roots are the axons of the motor cells located in the spinal cord and brain, and reach the innervated organ without interruption, and the sensitive ones are the axons of the nerve cells of the spinal nodes. To the periphery of the nodes, sensory and motor fibers form a mixed nerve.

All peripheral nerves, based on their anatomical features, are divided into cranial nerves - 12 pairs, spinal nerves - 31 pairs, autonomic (vegetative) nerves.

The cranial nerves arise from the brain and include:

• 1st pair - olfactory nerve
• 2nd pair - optic nerve
• 3rd pair - oculomotor nerve
• 4th pair - trochlear nerve
• 5th pair - trigeminal nerve
• 6th pair - abducens nerve
• 7th pair - facial nerve
• 8th pair - vestibulocochlear nerve
• 9th pair - glossopharyngeal nerve
• 10th pair - vagus nerve
• 11th pair - accessory nerve
• 12th pair - hypoglossal nerve

Through the peripheral nerve, the spinal ganglion and the posterior root, nerve impulses enter the spinal cord, that is, into the central nervous system.

Ascending fibers from a limited area of ​​\u200b\u200bthe body come together and form peripheral nerve. Fibers of all types (superficial and deep sensitivity, fibers innervating skeletal muscles, and fibers innervating internal organs, sweat glands and vascular smooth muscles) are combined into bundles surrounded by 3 connective tissue sheaths (endoneurium, perineurium, epineurium) and form a nerve cable.

After the peripheral nerve enters the spinal canal through the intervertebral foramen, it bifurcates into the anterior and posterior spinal roots.

The anterior roots leave the spinal cord, the posterior roots enter it. Within the nerve plexuses outside the spinal canal, the fibers of the peripheral nerves intertwine in such a way that eventually the fibers from one individual nerve end up at different levels within different spinal nerves.

The peripheral nerve contains fibers from several different radicular segments.

spinal nerves in the amount of 31 pairs are divided into:

• cervical nerves - 8 pairs
• thoracic nerves -12 pairs
• lumbar nerves - 5 pairs
• sacral nerves - 5 pairs
• coccygeal nerve - 1 pair

Each spinal nerve is a mixed nerve and is formed by the fusion of its 2 roots: the sensory root, or posterior root, and the motor root, or anterior root. In the central direction, each root is connected to the spinal cord by means of radicular filaments. The posterior roots are thicker and contain the spinal ganglion in their composition. The anterior roots of the nodes do not have. Most of the spinal nodes lie in the intervertebral foramen.

Externally, the spinal ganglion looks like a thickening of the posterior root, located slightly closer to the center from the confluence of the anterior and posterior roots. There are no synapses in the spinal ganglion itself.

By location in the body and functions, the nervous system is divided into peripheral and central. peripheral consists of individual nerve circuits and their groups that penetrate into all parts of our body and perform mainly a conductive function: the delivery of nerve signals from the sense organs (receptors) to the center and from it to the executive organs.

Central The nervous system consists of the brain and spinal cord. IN spinal cord the centers of a number of congenital unconditioned reflexes are located. It regulates the muscular movements of the human body and limbs, as well as the work of internal organs. main function brain- management, processing of information received from the periphery and the development of "commands" to the executive bodies.

Figure 3 - Plan of the structure of the nervous system

Functional asymmetry of the brain

It has been established that mental functions are distributed in a certain way between the left and right hemispheres. Both hemispheres are capable of receiving and processing information, both in the form of images and words, but there is functional asymmetry of the brain- different degree of manifestation of certain functions in the left and right hemispheres. The function of the left hemisphere is reading and counting, in general, the predominant operation of sign information (words, symbols, numbers, etc.). The left hemisphere provides the possibility of logical constructions, without which consistent analytical thinking is impossible. The right hemisphere operates with figurative information, provides orientation in space, perception of music, emotional attitude to perceived and understood objects. Both hemispheres function in interconnection. Functional asymmetry is inherent only to a person and is formed in the process of communication, in which a relative predominance of the functioning of the left or right hemisphere may develop in the individual, which affects his individual psychological characteristics.

The concept of reflex. Classification of reflexes by origin

The main form of interaction of the organism with the environment is reflex- the response of the body to irritation. This action is carried out with the help of the central nervous system.

Reflexes are of two types: congenital And acquired, or, according to the classification of I. P. Pavlov, unconditional(naturally conditioned, constantly acting), providing the rhythm of breathing and heartbeat, thermoregulation of the body, constriction and expansion of the pupil of the eye, blood filling of blood vessels, etc., and conditional, formed as a response to certain features of human life, ensuring its adaptation to a changing environment.

The unconditioned reflex is automatic and does not require any prior training. A conditioned reflex requires certain conditions for its occurrence and acts as the physiological basis of human knowledge.

So, for example, a small child reaches out with his hand to a shiny white teapot. Burned, the baby instantly withdraws his hand. This is an unconditioned reflex. But now he withdraws his hand at the mere sight of a teapot. This is a conditioned reflex.

Unconditioned and conditioned reflexes perform the function of connecting the organism with the environment, ensure its adaptation to this environment and normal life activity in it.

Nervous processes in the cerebral cortex. Types of braking. First and second signal systems

The coordination of the functions of the cerebral cortex is carried out due to the interaction of two main nervous processes - arousal And braking. By the nature of the activity, these processes are opposite to each other. If the processes of excitation are associated with the active activity of the cortex, with the formation of new conditioned nerve connections, then the processes of inhibition are aimed at changing this activity, at stopping the excitation that has arisen in the cortex, at blocking temporary connections. But one should not assume that inhibition is a cessation of activity, a passive state of nerve cells. Inhibition is also an active process, but of an opposite nature than excitation. Braking provides the necessary conditions for restoring their performance. Sleep has the same protective and restorative significance as inhibition, which has spread widely to a number of important areas of the cortex. Sleep protects the cortex from exhaustion and destruction. However, sleep is not a stop of the brain. I. P. Pavlov also noted that sleep is a kind of active process, and not a state of complete inactivity. During sleep, the brain is resting, but not inactive, while the cells that are active during the day are resting. Many scientists suggest that during sleep there is a kind of processing of information accumulated during the day, but a person is not aware of this, because the corresponding functional systems of the cortex that provide awareness are inhibited.

The cerebral cortex is affected by a variety of signals coming both from outside and from the body itself. IP Pavlov distinguished two fundamentally different types of signals (signal systems). Signals are, first of all, objects and phenomena of the surrounding world. I. P. Pavlov called these various visual, auditory, tactile, gustatory, olfactory stimuli first signal system. It is found in humans and animals.

But the human cerebral cortex is also capable of responding to words. Words and combinations of words also signal to a person about certain objects and phenomena of reality. Words and phrases I. P. Palov called second signal system. The second signal system is a product of human social life and is unique to him; animals do not have a second signal system.

Methods of scientific and psychological research

Methods of scientific and psychological research called a set of techniques and operations aimed at studying psychological phenomena and solving various scientific and psychological problems.

According to L.M. Fridman, methods of scientific and psychological research are divided into:

On non-experimental, describing a particular feature of an individual or a group of people. Non-experimental methods include: observation (self-observation), questioning, interviewing, conversation, analysis of performance results;

- diagnostic methods, which allow not only to describe certain mental characteristics of a person or group of people, but also measure them, give them qualitative and quantitative characteristics. Diagnostic methods include: testing, scaling, ranking, sociometry;

- experimental methods including natural, artificial, laboratory, field, ascertaining and formative experiments;

- formative methods, which allow, on the one hand, to study psychological characteristics, and on the other hand, to implement educational and educational tasks.

Questions for self-control

What is the subject of modern psychology?

What are the stages in the development of psychological science?

Why did psychology have its own subject of study at each stage of its development?

What was the originality of views on mental phenomena in ancient times?

What are the main ideas of ancient Greek philosophers about the soul?

Why did the ideas of R. Descartes serve as an important factor in the formation and development of scientific paradigms in psychology?

Who was the founder of scientific psychology? Prove it.

What is the subject of psychology from the point of view of classical behaviorism? What is the essence of this theory?

What are the main directions of development of domestic psychology?

Describe the main branches of psychology.

Expand the relationship of psychology and other sciences.

What was the name of the first method of scientific research in psychology and what methods were used in pre-scientific psychology?

What methods of scientific and psychological research are used by modern psychologists? What are the possibilities of these methods?

What main psychological schools appeared at the turn of the

third and fourth stages of development of psychology? What are their main characteristics?

Expand the scientific understanding of the human psyche.

Give a comparative analysis of the first and second signal systems.

Expand the understanding of the reflex as the main mechanism of higher nervous activity.

What do you understand by functional asymmetry of the brain?

What are the main functions of the psyche. In what forms does it appear?

Describe the basic principles of division of the human nervous system.

Tasks for independent work

Conduct a comparative analysis of psychological concepts at each stage of the development of psychology. Name the most, in your opinion, significant for the development of psychology as a science.

Learn more about the methods of scientific and psychological research in psychology textbooks. Apply survey methods in your practice, observing all the necessary requirements for conducting psychological research.

Departments of the nervous system

Anatomical division of departments nervous system:

(1) central nervous system (CNS) -

includes head And dorsal brain;

(2) peripheral nervous system - includes peripheral nerve ganglia (nodes), nerves And nerve endings(described in the section "Nervous tissue").

Physiological division of the departments of the nervous system(depending on the nature of the innervation of organs and tissues):

(1) somatic (animal) nervous system - controls mainly the functions of voluntary movement;

(2) autonomic (vegetative) nervous system - regulates the activity of internal organs, vessels and glands.

The autonomic nervous system is divided into interacting with each other sympathetic And parasympathetic divisions, which differ in the localization of peripheral nodes and centers in the brain, as well as the nature of the effect on internal organs.

The somatic and autonomic nervous system includes links located in the central nervous system and the peripheral nervous system. Functionally leading fabric organs of the nervous system is nervous tissue, including neurons and glia. Clusters of neurons in the CNS are commonly referred to as cores, and in the peripheral nervous system ganglia (nodes). Bundles of nerve fibers in the central nervous system are called paths, in the peripheral nerves.

Organs of the peripheral nervous system

Nerves(nerve trunks) connect the nerve centers of the brain and spinal cord with receptors and working organs. They are formed in bundles myelin And unmyelinated nerve fibers which are united by connective tissue components (shells): endoneurium, perineurium And epineurium(Fig. 114-118). Most nerves are mixed, that is, they include afferent and efferent nerve fibers.

Endoneurium- thin layers of loose fibrous connective tissue with small blood vessels, surrounding individual nerve fibers and linking them into a single bundle.

Perineurium- a sheath covering each bundle of nerve fibers from the outside and giving partitions deep into the bundle. It has a lamellar structure and is formed by concentric layers of flattened fibroblast-like cells connected by tight and gap junctions. Between the layers of cells in the spaces filled with liquid, there are components of the basement membrane and longitudinally oriented collagen fibers.

epineurium- the outer sheath of the nerve that binds bundles of nerve fibers together. It consists of dense fibrous connective tissue containing fat cells, blood and lymph vessels (see Fig. 114).

Nerve structures revealed by various staining methods. Various histological staining methods allow more detailed and selective study of individual components

nerve. So, osmization gives contrast staining of the myelin sheaths of nerve fibers (allowing to assess their thickness and differentiate between myelinated and non-myelinated fibers), but the processes of neurons and connective tissue components of the nerve remain very weakly stained or unstained (see Fig. 114 and 115). When painting hematoxylin-eosin myelin sheaths are not stained, the processes of neurons have a slightly basophilic staining, however, the nuclei of neurolemmocytes in nerve fibers and all connective tissue components of the nerve are well detected (see Fig. 116 and 117). At stained with silver nitrate the processes of neurons are brightly stained; myelin sheaths remain unstained, the connective tissue components of the nerve are poorly detected, their structure is not traced (see Fig. 118).

Nerve ganglia (nodes)- structures formed by clusters of neurons outside the CNS - are divided into sensitive And autonomous(vegetative). Sensory ganglia contain pseudo-unipolar or bipolar (in the spiral and vestibular ganglia) afferent neurons and are located mainly along the posterior roots of the spinal cord (sensory nodes of the spinal nerves) and some cranial nerves.

Sensory ganglia (knots) of the spinal nerves spindle-shaped and covered capsule of dense fibrous connective tissue. On the periphery of the ganglion are dense clusters of bodies pseudounipolar neurons, and the central part is occupied by their processes and thin layers of endoneurium located between them, bearing vessels (Fig. 121).

Pseudo-unipolar sensory neurons are characterized by a spherical body and a light nucleus with a clearly visible nucleolus (Fig. 122). The cytoplasm of neurons contains numerous mitochondria, cisterns of the granular endoplasmic reticulum, elements of the Golgi complex (see Fig. 101), and lysosomes. Each neuron is surrounded by a layer of flattened oligodendroglia cells adjacent to it. or mantle gliocytes) with small rounded nuclei; outside the glial membrane there is a thin connective tissue capsule (see Fig. 122). A process departs from the body of a pseudounipolar neuron, dividing in a T-shaped manner into peripheral (afferent, dendritic) and central (efferent, axonal) branches, which are covered with myelin sheaths. peripheral process(afferent branch) ends with receptors,

central process(efferent branch) as part of the posterior root enters the spinal cord (see Fig. 119).

Autonomic nerve ganglia formed by clusters of multipolar neurons, on which numerous synapses form preganglionic fibers- processes of neurons whose bodies lie in the central nervous system (see Fig. 120).

Classification of autonomous ganglia. By localization: ganglia can be located along the spine (paravertebral ganglia) or ahead of him (prevertebral ganglia) as well as in the wall of organs - the heart, bronchi, digestive tract, bladder, etc. (intramural ganglia- see, for example, fig. 203, 209, 213, 215) or near their surface.

Functionally, autonomic nerve ganglia are divided into sympathetic and parasympathetic. These ganglia differ in their localization (sympathetic lie para- and prevertebral, parasympathetic lie intramurally or near organs), as well as the localization of neurons that give rise to preganglionic fibers, the nature of neurotransmitters and the direction of reactions mediated by their cells. Most internal organs have dual autonomic innervation. The general plan of the structure of the sympathetic and parasympathetic nerve ganglia is similar.

The structure of the autonomous ganglia. The autonomous ganglion is externally covered with connective tissue. capsule and contains diffuse or clustered bodies multipolar neurons, their processes in the form of non-myelinated or (rarely) myelinated fibers and endoneurium (Fig. 123). The bodies of neurons are basophilic, irregular in shape, contain an eccentrically located nucleus; there are multinucleated and polyploid cells. Neurons are surrounded (usually incompletely) by sheaths of glial cells (satellite glial cells, or mantle gliocytes). Outside of the glial membrane is a thin connective tissue membrane (Fig. 124).

intramural ganglia and the pathways associated with them, due to their high autonomy, the complexity of the organization and the peculiarities of the mediator exchange, are distinguished by some authors as an independent metasympathetic division autonomic nervous system. Three types of neurons are described in the intramural ganglia (see Fig. 120):

) Long-axon efferent neurons (type I Dogel cells) with short dendrites and a long axon extending beyond the node

to the cells of the working organ, on which it forms motor or secretory endings.

2) Equal outgrowth afferent neurons (type II Dogel cells) contain long dendrites and an axon that extends beyond this ganglion into neighboring ones and forms synapses on cells of types I and III. They are part of the local reflex arcs as a receptor link, which are closed without a nerve impulse entering the central nervous system.

3) Association cells (Dogel type III cells)- local intercalary neurons, connecting several cells of types I and II with their processes. The dendrites of these cells do not go beyond the node, and the axons go to other nodes, forming synapses on type I cells.

Reflex arcs in the somatic (animal) and autonomic (vegetative) parts of the nervous system have a number of features (see Fig. 119 and 120). The main differences lie in the associative and effector links, since the receptor link is similar: it is formed by afferent pseudo-unipolar neurons, whose bodies are located in sensory ganglia. The peripheral processes of these cells form sensory nerve endings, while the central processes enter the spinal cord as part of the posterior roots.

Associative link in the somatic arc it is represented by intercalary neurons, the dendrites and bodies of which are located in posterior horns of the spinal cord and axons go to front horns, transmitting impulses to the bodies and dendrites of efferent neurons. In the autonomous arc, the dendrites and bodies of the intercalary neurons are located in lateral horns of the spinal cord and axons (preganglionic fibers) leave the spinal cord as part of the anterior roots, heading to one of the autonomous ganglia, where they end on the dendrites and bodies of efferent neurons.

Effector link in the somatic arch it is formed by multipolar motor neurons, the bodies and dendrites of which lie in the anterior horns of the spinal cord, and the axons leave the spinal cord as part of the anterior roots, go to the sensory ganglion and then, as part of the mixed nerve, to the skeletal muscle, on the fibers of which their branches form neuromuscular synapses. In the autonomous arc, the effector link is formed by multipolar neurons, the bodies of which lie in the autonomous ganglia, and the axons (postganglionic fibers) as part of the nerve trunks and their branches are sent to the cells of the working organs - smooth muscles, glands, heart.

Rice. 121. Sensory ganglion of the spinal nerve

Stain: hematoxylin-eosin

1 - back spine; 2 - sensitive ganglion of the spinal nerve: 2.1 - connective tissue capsule, 2.2 - bodies of pseudo-unipolar sensory neurons, 2.3 - nerve fibers; 3 - front spine; 4 - spinal nerve

Rice. 122. Pseudo-unipolar neuron of the sensory ganglion of the spinal nerve and its tissue microenvironment

Stain: hematoxylin-eosin

1 - body of a pseudo-unipolar sensitive neuron: 1.1 - nucleus, 1.2 - cytoplasm; 2 - satellite glial cells; 3 - connective tissue capsule around the body of the neuron

Rice. 123. Autonomous (vegetative) ganglion from the solar plexus

1 - preganglionic nerve fibers; 2 - autonomous ganglion: 2.1 - connective tissue capsule, 2.2 - bodies of multipolar autonomic neurons, 2.3 - nerve fibers, 2.4 - blood vessels; 3 - postganglionic fibers

Rice. 124. Multipolar neuron of the autonomic ganglion and its tissue microenvironment

Stain: iron hematoxylin

1 - body of a multipolar neuron: 1.1 - nucleus, 1.2 - cytoplasm; 2 - the beginning of processes; 3 - gliocytes; 4 - connective tissue sheath