What is the central and peripheral nervous system. Organs of the peripheral nervous system. Dorsal nerves of the cervical spine

Correct functioning of the nervous system on different fronts is extremely important for a fulfilling human life. The human nervous system is considered the most complex structure of the body.

Modern ideas about the functions of the nervous system

The complex communication network, which in biological science is designated as the nervous system, is divided into central and peripheral, depending on the location of the nerve cells themselves. The first combines cells located inside the brain and spinal cord. But the nerve tissues that are located outside of them form the peripheral nervous system (PNS).

The central nervous system (CNS) implements the key functions of processing and transmitting information, interacts with the environment... works according to the reflex principle. A reflex is an organ's response to a specific stimulus. The nerve cells of the brain are directly involved in this process. Having received information from the neurons of the PNS, they process it and send an impulse to the executive organ. According to this principle, all voluntary and involuntary movements are carried out, the sense organs (cognitive functions) work, thinking and memory function, etc.

Cellular mechanisms

Regardless of the functions of the central and peripheral nervous systems and the location of cells, neurons share some characteristics in common with all cells in the body. So, each neuron consists of:

• membranes, or the cytoplasmic membrane;
• cytoplasm, or the space between the membrane and the nucleus of the cell, which is filled with intracellular fluid;
• mitochondriathat provide the neuron itself with the energy they receive from glucose and oxygen;
• microtube - thin structures that perform supporting functions and help the cell to maintain its primary shape;
• endoplasmic reticulum - internal networks that the cell uses for self-sufficiency.

Distinctive features of nerve cells

Nerve cells have specific elements that are responsible for their communication with other neurons.

Axons - the main processes of nerve cells, through which information is transmitted along the neural circuit. The more outgoing channels of information transmission a neuron forms, the more branches its axon has.

Dendrites - others They have input synapses - specific points where contact with neurons occurs. Therefore, the incoming neural signal is called synoptic transmission.

Classification and properties of nerve cells

Nerve cells, or neurons, are divided into many groups and subgroups, depending on their specialization, functionality, and place in the neural network.

The elements responsible for sensory perception of external stimuli (sight, hearing, tactile sensations, smell, etc.) are called sensory. The neurons that network together to provide motor functions are called motor neurons. Also, there are mixed neurons in the neural network that perform universal functions.

Depending on the location of the neuron in relation to the brain and the executive organ, cells can be primary, secondary, etc.

Genetically, neurons are responsible for the synthesis of specific molecules, with the help of which they build synaptic connections with other tissues, but nerve cells do not have the ability to divide.

This is the basis of the statement, widespread in the literature, that “nerve cells do not recover”. Naturally, neurons unable to divide cannot regenerate. But every second they are able to create many new neural connections to perform complex functions.

Thus, cells are programmed to constantly create new connections. This is how complex communications develop. The creation of new connections in the brain leads to the development of intelligence, thinking. Muscular intelligence also develops in a similar way. The brain is irreversibly improved while learning more and more new motor functions.

The development of emotional intelligence, physical and mental, occurs in the nervous system in a similar way. But if the emphasis is on one thing, other functions develop less rapidly.

Brain

The adult brain weighs approximately 1.3-1.5 kg. Scientists have found that until the age of 22, its weight gradually increases, and after 75 years it begins to decrease.

There are more than 100 trillion electrical connections in the brain of the average individual, which is several times more than all connections in all electrical devices in the world.

Researchers spend tens of years and tens of millions of dollars on studying and trying to improve brain functions.

Parts of the brain, their functional characteristics

Nevertheless, modern knowledge about the brain can be considered sufficient. Especially considering that the ideas of science about the functions of individual parts of the brain made possible the development of neurology, neurosurgery.

The brain is divided into the following zones:

1. Forebrain. The regions of the forebrain are usually ascribed to "higher" thinking functions. It includes:

• the frontal lobes, which are responsible for coordinating the functions of other areas;
• those responsible for hearing and speech;
• the parietal lobes regulate movement control and sensory perception.
• the occipital lobes are responsible for visual function.

2. The midbrain includes:

• Thalamus, where almost all information entering the forebrain is processed.
• The hypothalamus controls information from the organs of the central and peripheral nervous system and the autonomic NS.

3. The hindbrain includes:

Spinal cord

The average length of the spinal cord in an adult is approximately 44 cm.

It originates from the brainstem and passes through the foramen magnum in the skull. It ends at the level of the second lumbar vertebra. The end of the spinal cord is called the cone of the brain. It ends with an accumulation of lumbar and sacral nerves.

From the spinal cord, 31 pairs of spinal nerves branch out. They help to connect the parts of the nervous system: central and peripheral. Through these processes, parts of the body and internal organs receive signals from the NS.

In the spinal cord, the primary processing of reflex information also takes place, due to which the process of a person's response to stimuli in dangerous situations is accelerated.

CSF, or cerebral fluid, common to the spinal cord and brain, is formed in the vascular nodes of the clefts of the brain from blood plasma.

Normally, its circulation should be continuous. CSF creates constant internal cranial pressure, performs shock-absorbing and protective functions. Analysis of the composition of the cerebrospinal fluid is one of the simplest ways to diagnose serious NS diseases.

What do lesions of the central nervous system of various origins lead to?

The lesions of the nervous system, depending on the period, are divided into:

1. Pre-perinatal - brain damage during intrauterine development.
2. Perinatal - when the lesion occurs during childbirth and in the first hours after birth.
3. Postnatal - when damage to the spinal cord or brain occurs after birth.

Depending on the nature, the lesions of the central nervous system are divided into:

1. Traumatic (most obvious). It must be taken into account that the nervous system is of paramount importance for living organisms and from the point of view of evolution, therefore, the spinal cord and brain are reliably protected by a number of membranes, peri-cerebral fluid and bone tissue. However, in some cases, this protection is insufficient. Some injuries damage the central and peripheral nervous systems. Traumatic lesions of the spinal cord more often lead to irreversible consequences. Most often these are paralysis, moreover, degenerative (accompanied by the gradual death of neurons). The higher the damage, the more extensive the paresis (decrease in muscle strength). Open and closed concussions are considered the most common injuries.
2. Organic damage to the central nervous system often occurs during childbirth and leads to cerebral palsy. They arise due to oxygen starvation (hypoxia). It is the result of prolonged labor or entanglement with the umbilical cord. Depending on the period of hypoxia, cerebral palsy can be of different degrees of severity: from mild to severe, which is accompanied by complex atrophy of the functions of the central and peripheral nervous system. Damage to the central nervous system after stroke is also defined as organic.
3. Genetically determined lesions of the central nervous system occur due to mutations in the gene chain. They are considered hereditary. The most common are Down syndrome, Tourette's syndrome, autism (genetic metabolic disorder), which appear immediately after birth or in the first year of life. Diseases of Kensington, Parkinson's, Alzheimer's are considered degenerative and manifest in middle or old age.
4. Encephalopathy - most often occur as a result of damage to brain tissue by pathogens (herpetic encephalopathy, meningococcal, cytomegalovirus).

The structure of the peripheral nervous system

The PNS is formed by nerve cells located outside the brain and spinal canal. It consists of (cranial, spinal and vegetative). There are also 31 pairs of nerves and nerve endings in the PNS.

In a functional sense, PNS consists of somatic neurons, which transmit motor impulses and contact with receptors of the sense organs, and vegetative, which are responsible for the activity of internal organs. Peripheral neural structures contain motor, sensory, and vegetative fibers.

Inflammatory processes

Diseases of the central and peripheral nervous systems are completely different in nature. If CNS damage most often has complex, global consequences, then PNS diseases often manifest themselves as inflammatory processes in the zones of nerve nodes. In medical practice, such inflammation is called neuralgia.

Neuralgia - These are painful inflammations in the area of \u200b\u200baccumulation of nerve nodes, irritation of which causes an acute reflexive attack of pain. Neuralgias include polyneuritis, radiculitis, inflammation of the trigeminal or lumbar nerve, plexitis, etc.

The role of the central and peripheral nervous system in the evolution of the human body

The nervous system is the only system of the human body that can be improved. The complex structure of the central and peripheral nervous system of a person is determined genetically and evolutionarily. The brain has a unique property - neuroplasticity. This is the ability of CNS cells to take on the functions of neighboring dead cells, building new neural connections. This explains the medical phenomena when children with organic brain damage develop, learn to walk, speak, etc., and after a stroke, people eventually recover the ability to move normally. All this is preceded by the construction of millions of new connections between the central and peripheral parts of the nervous system.

With the progress of various techniques for the recovery of patients after brain injury, techniques for the development of human potential are also being born. They are based on the logical assumption that if both the central and peripheral nervous systems can recover from injury, then healthy nerve cells are also capable of developing their potential almost indefinitely.

(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), sensitive ganglia, nerve plexuses (see Cervical plexus, Brachial plexus, Lumbosacral plexus), peripheral nerve trunks of the trunk and limbs, right and left sympathetic trunks, ganglia and nerves. The conventionality 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 a segment of the spinal cord, or dendrites of sensory neurons of the intervertebral ganglia (the axons of these cells are directed along the dorsal roots in). 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 make up the central nervous system. (for sensitive cells). Main P. n. from. is to provide communication c.s.s. with the external environment and target organs. It is carried out either by conduction of nerve impulses 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 c.ns. to the muscles that ensure the movement of the body in the surrounding space, to the internal organs and systems. P.'s structures of n. from. have their own vascular and innervation support, supporting the trophism of nerve fibers and ganglia; as well as its own cerebrospinal fluid system in the form of capillary gaps along the nerves and plexuses. It is formed starting from the intervertebral ganglia (directly in front of which on the spinal roots it ends in blind sacs with cerebrospinal fluid that bathes the central nervous system). Thus, both cerebrospinal fluid systems (central and peripheral nervous systems) are separate and have a kind of barrier between each other at the level of the intervertebral ganglia. In the peripheral nervous system, nerve trunks can contain motor fibers (anterior roots of the spinal cord, facial, abducens, block, accessory and sublingual), 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 vegetative fibers). Mixed nerves include intercostal nerves, trunks of the cervical, brachial and lumbosacral plexuses and the nerves emanating from them 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 contains the median and tibial nerves, as well as the vagus nerve. Despite the external disunity, separate nervous trunks of P. of N. with., between them there is a certain functional relationship, provided by nonspecific structures of c.ns. One or another of a separate nerve trunk affects the functional state of not only the symmetrical nerve, but also the distant nerves on its own and the opposite side of the body: in the experiment, the contralateral neuromuscular preparation increases, and in the clinic - with mononeuritis, the conductance parameters along other nerve trunks increase. The specified functional relationship to some extent (along with other factors) determines the N characteristic of P. from. multiple lesions of its structures - polyneuritis and, polyganglionitis, etc.

P.'s defeat of N. from. can be caused by a variety of factors: trauma, metabolic and vascular disorders, infections, intoxication (household, industrial and medicinal), vitamin deficiency and other deficiency conditions. A large group of P.'s diseases. from. are hereditary polyneuropathies: neural Charcot - Marie - Tooth (see Amyotrophies), Russi - Levy syndrome, hypertrophic polyneuropathies of Dejerine - Sott and Marie - Boveri, etc. In addition, a number of hereditary diseases of c.ns. is accompanied by P.'s defeat by N. from: family Friedreich (see Ataxia), family Strumpell (see Paraplegia (Paraplegia)), ataxia-telangiectasia Louis-Bar, etc. Depending on the primary localization of P.'s defeat of N. from. distinguish Radiculitis, Plexites, Ganglionitis, Neuritis, as well as associated lesions - polyradiculoneuritis, polyneuritis (Polyneuropathy). The most common cause of radiculitis is metabolic dystrophic changes in the spine with osteochondrosis, herniated intervertebral 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 primarily affected by the herpes virus. A large group of compression defeats of P. of N is described. N of page associated with compression of its structures in fibrous, bone, muscle canals (Tunnel syndromes). defeat of P.'s structures of N from. due to the involvement of motor, sensory and autonomic fibers that are part of the nerve trunks (, paresis, muscle atrophy, disorders of superficial and deep sensitivity in the zone of disturbed innervation in the form of pain, paresthesias, anesthesia, causalgia syndromes and phantom sensations, vegetative-vascular and trophic disorders more often in the distal extremities). A separate group is made up of pain syndromes, which often proceed in isolation, not accompanied by symptoms of loss of functions - neuralgia, plexalgia, radiculalgia. The most severe pain syndromes are observed in ganglionitis (sympathetic), as well as injuries of the median and tibial nerves with the development of causalgia (Causalgia).

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

P.'s tumors of N. from. (neuromas, neurofibromas, glomus) are relatively rare, but can occur at various levels.

Diagnostics of P.'s defeats of N. from. based primarily on the data of the patient's clinical examination. Characterized mainly by distal paralysis and paresis with impaired sensitivity, vegetative-vascular and trophic disorders in the zone of innervation of one or another nerve trunk. When peripheral nerve trunks are damaged, thermal imaging studies have 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. Electrodiagnostics and chronaximetry are also performed, 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 speeds of the impulse along the nerves allows you to determine the exact localization of the lesion of the nerve trunk by their decrease, as well as to reveal the degree of involvement in motor or sensory nerve fibers. For P.'s defeat of N. from. also characterized by a decrease in the amplitudes of the evoked potentials of the affected nerve and denervated muscles. To clarify the nature of the pathological process in polyneuropathies, nerve tumors, a biopsy of the cutaneous nerves is used, followed by their histological and histochemical examination. For clinically diagnosed tumors of the nerve trunks, computed tomography (Tomography) can be used, which has special meaning in cases of tumors of the cranial nerves (for example, with neuroma of the auditory nerve). Computer allows to establish the localization of the intervertebral disc, which is important for its subsequent prompt removal.

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

Bibliography.: Badalyan L.O. and Skvortsov I.A. Clinical electroneuromyography, M., 1986; Gusev E.I., Grechko V.E. and Buriag 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.

See what "" is in other dictionaries:

The human nervous system. The peripheral nervous system is highlighted in blue, and the central nervous system is highlighted in red. The peripheral nervous system ... Wikipedia

Peripheral nervous system - includes 31 pairs of spinal nerves and 12 pairs of cranial nerves, heading from the spinal cord and brain to the periphery. Cranial Nerves Spinal Nerves * * * See also: Nervous system Central nervous system Spinal cord ... ... Human Anatomy Atlas

PERIPHERAL NERVOUS SYSTEM, all parts of the NERVOUS SYSTEM lying outside the CENTRAL NERVOUS SYSTEM (CNS). Consists of 12 pairs of cranial nerves that control the head and neck region, and 31 pairs of spinal nerves, the fibers of which stretch ... Scientific and technical encyclopedic dictionary

- (systema nervosum periphericum), part of the nervous system, represented by nerves that connect the central nervous system with sensory organs, repeaters and effectors (muscles, glands). In vertebrates, it consists of cranial and spinal nerves, as well as ... ... Biological encyclopedic dictionary

peripheral nervous system - periferinė nervų sistema statusas T sritis Kūno kultūra ir sportas apibrėžtis Nervų sistemos dalis, kurią sudaro nervai, nervų šaknelės, nerviniai rezginiai ir mazgai (ganglijai), ryš aitskiri tarp

PERIPHERAL NERVOUS SYSTEM - See the nervous system ... Explanatory Dictionary of Psychology

Peripheral nervous system - a part of the functionally unified nervous system of vertebrates and humans, formed by a set of nerves ... Encyclopedic Dictionary of Psychology and Pedagogy

PERIPHERAL NERVOUS SYSTEM - the division of the nervous system, which includes the cranial nerves, spinal nerves and nerve plexuses. These nerve formations deliver impulses from the central nervous system directly to the working organs of the muscles and information from the periphery to the central nervous system ... Psychomotor: dictionary-reference

nervous system - (from the grim. n ё u gop nerve and sistema whole, composed of parts) a set of all elements of the nervous tissue of living organisms, interconnected and providing a response to external and internal stimuli. N. s. provides ... ... Great psychological encyclopedia

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: 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 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 executive bodies.

Figure 3 - Plan of the structure of the nervous system

Functional asymmetry of the brain

It was found that mental functions are distributed in a certain way between the left and right hemispheres. Both hemispheres are able to receive and process information, both in the form of images and words, but there is functional asymmetry of the brain - different degrees of severity of certain functions in the left and right hemispheres. The function of the left hemisphere is reading and counting, in general, predominantly operating with 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 a relationship. Functional asymmetry is inherent only in humans and is formed in the process of communication, in which a relative predominance of the functioning of the left or right hemisphere in a person can develop, which affects his individual psychological characteristics.

Reflex concept. 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 by the central nervous system.

Reflexes by their origin are of two types: congenital and acquired, or, according to the classification of I.P. Pavlov, unconditional(natural, constantly acting), providing the rhythm of respiration and heartbeat, thermoregulation of the body, constriction and expansion of the pupil of the eye, blood circulation in blood vessels, etc., and conditional,formed as a response to certain features of human life, ensuring his adaptation to a changing environment.

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

For example, a small child reaches out with his hand to a shiny white teapot. Having been burned, the baby instantly withdraws his hand. This is an unconditioned reflex. But now he jerks his hand away at the sight of the teapot. This is a conditioned reflex.

Unconditioned and conditioned reflexes perform the function of the body's connection with the environment, ensure its adaptation to this environment and normal life in it.

Nervous processes in the cortex of the cerebral hemispheres. Braking types. First and second signaling systems

The coordination of the functions of the cerebral cortex is carried out through the interaction of two main nervous processes - excitement and braking... By the nature of their 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 arousal. Braking provides the necessary conditions to restore their performance. Sleep has the same protective and restorative significance as inhibition, which is widespread in a number of important areas of the cortex. Sleep protects the bark from exhaustion and destruction. However, sleep is not a halt in the brain. Even IP Pavlov noted that sleep is a kind of active process, and not a state of complete inactivity. In sleep, the brain rests, but does not stay idle, while the cells that are active during the day rest. Many scientists assume that during sleep there is a kind of processing of the information accumulated during the day, but a person does not realize this, since the corresponding functional systems of the cortex that provide awareness are inhibited.

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

But the human cerebral cortex can also respond to words. Words and word combinations also signal a person about certain objects and phenomena of reality. I.P. Palov named words and phrases second signaling system... The second signaling system is a product of human social life and is inherent only in it, animals do not have a second signaling system.

Methods of scientific and psychological research

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

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

On the non-experimental, allowing to describe any feature of a person 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 a 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 the psychological characteristics, and on the other, to implement educational and educational tasks.

Questions for self-control

What is the subject of modern psychology?

What stages of the formation of psychological science are distinguished?

Why did psychology have its own subject of research at every stage of its development?

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

What are the main ideas of the 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.

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

What are the main directions of development of Russian psychology?

Describe the main branches of psychology.

Expand the relationship between 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 are the main psychological schools that appeared at the turn

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 signaling systems.

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

What do you mean by functional asymmetry of the brain?

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

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

Self-study assignments

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.

FEDERAL STATE BUDGET

EDUCATIONAL INSTITUTION OF HIGHER PROFESSIONAL EDUCATION "MORDOVSK STATE UNIVERSITY

NAME. N. P. OGAREVA "

Department of Biology

Physiology of the peripheral nervous system

Saransk 2013

Introduction

The structure of the peripheral nervous system

Spinal peripheral nerves

Nerve endings of the peripheral nervous system

Conclusion

Introduction

The peripheral nervous system consists of nerves that connect the central nervous system (CNS) with the sense organs, muscles, and glands. The nerves are divided into spinal and cranial. Nerve nodes (ganglia), small clusters of neurons outside the central nervous system, can be located along their course. The nerves connecting the central nervous system with the sensory organs and muscles are referred to as the somatic nervous system, and with the internal organs, blood vessels, glands - to the autonomic nervous system.

The purpose of our work: to characterize the structure, properties and functions of the peripheral nervous system.

To achieve this goal, a number of tasks had to be solved:

Determine the parts of the peripheral nervous system.

Give morphological characteristics of the peripheral nervous system.

Reveal the functional features of the peripheral nervous system.

1. The structure of the peripheral nervous system

The peripheral nervous system is part of the nervous system. It is located outside the brain and spinal cord, provides two-way communication of the central parts of the nervous system with organs and body systems.

The peripheral nervous system includes the cranial and spinal nerves, sensory nodes of the cranial and spinal nerves, nodes (ganglia) and nerves of the autonomic (autonomic) nervous system and, in addition, a number of elements of the nervous system, with the help of which external and internal stimuli (receptors and effectors).

Nerves are formed by the processes of nerve cells, the bodies of which lie within the brain and spinal cord, as well as in the nerve nodes of the peripheral nervous system. Outside, the nerves are covered with a loose connective tissue sheath - epineurium. In turn, the nerve consists of bundles of nerve fibers covered with a thin sheath - perineurium, and each nerve fiber - endoneurium.

Peripheral nerves can vary in length and thickness. The longest cranial nerve is the vagus nerve. It is known that the peripheral nervous system connects the brain and spinal cord with other systems using two types of nerve fibers - centripetal and centrifugal. The first group of fibers conducts impulses from the periphery to the central nervous system and is called sensory (efferent) nerve fibers, the second carries impulses from the central nervous system to an innervated organ - these are motor (afferent) nerve fibers.

Depending on the innervated organs, the efferent fibers of the peripheral nerves can perform the motor function - they innervate the muscle tissue; secretory - the glands innervate; trophic - provide metabolic processes in tissues. There are motor, sensory and mixed nerves.

The motor nerve is formed by the processes of nerve cells located in the nuclei of the anterior horns of the spinal cord or in the motor nuclei of the cranial nerves.

The sensory nerve is made up of nerve cell processes that form the spinal cranial nerve nodes.

Mixed nerves contain both sensory and motor nerve fibers.

Autonomic nerves and their branches are formed by processes of cells of the lateral horns of the spinal cord or autonomic nuclei of the cranial nerves. The processes of these cells are prenodal nerve fibers and go to the autonomic (autonomic) nodes, which are part of the autonomic nerve plexuses. The processes of the cells of the nodes are directed to the innervated organs and tissues and are called postnodal nerve fibers.

Cranial peripheral nerves

The nerves that extend from the brain stem are called cranial nerves. In humans, 12 pairs of cranial nerves are isolated, they are denoted by Roman numerals in order of location. The cranial nerves have different functions, as they are composed only of motor or sensory nerves, or of two types of nerve fibers. Therefore, one part of them belongs to motor nerves (III, IV, VI, XI and XII pairs), the other to sensitive (I, II, VIII pairs), and the third is mixed (V, VII, IX and X pairs).

Olfactory nerves (nn. Olfactorii) - I pair of cranial nerves (Fig. 1).

Figure: 1. Olfactory nerve:

Olfactory bulbs; 2- olfactory nerves

By function, they are sensitive and are formed by the central processes of the olfactory cells located in the mucous membrane of the nasal cavity. These processes form nerve fibers, which, in the composition of 15-20 olfactory nerves, go through the holes of the ethmoid plate into the cranial cavity into the olfactory bulb.

Optic nerve (n. Opticus) - II pair of sensory nerves (Fig. 2).

Figure: 2. Optic nerve (diagram):

Eyeball; 2 - optic nerve; 3 - orbital part; 4 - intra-tubular part; 5 - intracranial part; 6 - visual crossover.

It is represented by neurites of the ganglionic nerve cells of the retina of the eyeball. Having passed through the choroid, the sclera, the optic nerve canals penetrate into the cranial cavity, where they form an incomplete optic chiasm (chiasm). After crossing, nerve fibers are collected in the optic tracts.

Oculomotor nerve (item oculomotorius) - III pair. One part of the nerve originates from the motor nucleus, the other from the autonomic (parasympathetic) nucleus, located in the midbrain. It goes to the base of the skull from the groove of the same name to the medial surface of the brain stem and through the superior palpebral fissure it enters the orbit, where it is divided into two branches: upper and lower; innervates the muscles of the eye. Vegetative fibers extend from the lower branch of the oculomotor nerve and form the oculomotor (parasympathetic) root, which is directed to the ciliary node

Block nerve (item trochlearis), IV pair, is a motor nerve. It starts from the nucleus of the midbrain, emerges from the dorsal surface of the brainstem and goes along the base of the skull to the orbit. In the orbit, the nerve penetrates through the superior palpebral fissure, reaches the superior oblique muscle. The trigeminal nerve (item trigeminus), V pair, is the mixed nerve. The motor fibers of the trigeminal nerve begin from its motor nucleus, which lies in the bridge.

Sensory fibers of this nerve go to the nuclei of the midbrain and spinal pathways of the trigeminal nerve.

The nerve comes out to the base of the brain from the lateral surface of the pons by two roots: sensory and motor. On the anterior surface of the pyramid of the temporal bone, it forms a thickening of the sensitive root of the trigeminal nerve - the trigeminal node. This node is represented by the bodies of sensory neurons, the central processes of which form the sensitive root, and the peripheral ones are involved in the formation of all three branches of the trigeminal nerve extending from the trigeminal node: 1) the optic nerve; 2) the maxillary nerve and 3) the mandibular nerve. The first two branches are sensitive in composition, the third is mixed, since motor fibers are attached to it.

The first branch, the optic nerve, passes into the orbit through the superior optic fissure, where it divides into three main branches; and nervate the contents of the orbit, the eyeball, the skin and conjunctiva of the upper eyelid, the skin of the forehead, nose, the mucous membrane of the part of the nasal cavity, frontal, sphenoid sinuses. eyes and innervates her.

The second branch, the maxillary nerve, passes through the round opening into the pterygo-palatine fossa, where the infraorbital and zygomatic nerves branch off from it, as well as the nodal branches to the pterygopalatine node.

The infraorbital nerve gives off branches for innervation of the teeth, gums of the upper jaw; innervates the skin of the lower eyelid, nose, upper lip.

The zygomatic nerve gives branches from the parasympathetic fibers to the lacrimal gland along the way, and also innervates the skin of the temporal, zygomatic and buccal regions. Branches extend from the pterygopalatine node, which innervate the mucous membrane and glands of the nasal cavity, hard and soft palate.

The third branch, the mandibular nerve, leaves the skull through the foramen ovale and divides into a number of motor branches to all the masticatory muscles, the maxillary-hyoid muscle, which strains the palatine curtain, and to the muscle that strains the eardrum. In addition, the mandibular nerve gives off a number of sensitive branches, including large ones: the lingual and lower alveolar nerves; smaller nerves (buccal, ear-temporal, meningeal branch). The latter innervate the skin and mucous membrane of the cheeks, part of the auricle, the external auditory canal, the eardrum, the skin of the temporal region, the parotid salivary gland, and the lining of the brain.

The lingual nerve perceives the general sensitivity of the mucous membrane (pain, touch, temperature) from 2/3 of the tongue and oral mucosa.

The inferior alveolar nerve, the largest of all the branches of the mandibular nerve, enters the canal of the mandible, innervates the teeth and gums of the mandible and, passing through the chin foramen, innervates the skin of the chin and lower lip.

The abducens nerve (item abducens), pair VI (Fig. 126), is formed by the axons of the motor cells of the nucleus of this nerve, lies in the posterior part of the bridge at the bottom of the IV ventricle. The nerve originates from the brain stem, passes into the orbit through the superior palpebral fissure, and innervates the external rectus muscle of the eye.

The facial nerve (n. Facialis), VII pair, is a mixed nerve that unites two nerves: the facial and intermediate nerves. The nuclei of the facial nerve lie within the boundaries of the pons of the brain. Coming out of the brain stem in the groove between the bridge and the medulla oblongata, the facial nerve enters the internal auditory canal and, after passing through the facial canal, exits through the styloid foramen.

In the facial canal, the nerve is divided into a number of branches:

1) a large petrosal nerve, which carries parasympathetic fibers to the pterygo-palatine node; it leaves the channel through an opening on the upper surface of the pyramid;

2) the tympanic string - a mixed nerve, departs from the facial nerve through the basal-stone fissure and goes forward and downward until it connects with the lingual nerve. The nerve contains afferent taste fibers from the front of the tongue and parasympathetic salivary fibers to the sublingual and submandibular salivary glands; 3) the stapedial nerve - the motor nerve, innervates the stapedius muscle of the tympanic cavity.

The facial nerve, when leaving its canal through the styloid opening, gives off branches to the supracranial muscle, posterior ear muscle, digastric and stylohyoid muscles. In the thickness of the parotid gland, the facial nerve fan-shapedly splits into branches and forms a large crow's feet - the parotid plexus. Only motor fibers leave this plexus and form the next branches - temporal, zygomatic, buccal, red branch of the lower jaw, cervical. All of them are involved in the innervation of the facial muscles of the face and the subcutaneous muscle of the neck.

The vestibular cochlear nerve (item vestibulocochlearis), pair VIII, is formed by sensitive nerve fibers that come from the organ of hearing and balance. It leaves the brain stem behind the bridge, lateral to the facial nerve and is divided into the vestibular and cochlear parts, which provide innervation to the organ of hearing and balance.

The vestibule of the nerve lies in the vestibule of the node located at the bottom of the internal auditory canal. The peripheral processes of these cells form a series of nerves, which end in receptors in the semicircular canals of the membranous labyrinth of the inner ear, and the central processes are directed to the nuclei of the same name in the rhomboid fossa. The vestibule is involved in the regulation of the position of the head, trunk and limbs in space, as well as in the system of coordination of movements.

The cochlear part of the nerve is formed by the central processes of the neurons of the cochlear node, which lies in the cochlea labyr? Nta. The peripheral processes of the cells of this node end in the spiral organ of the cochlear duct, and the central processes reach the nuclei of the same name, which lie in the rhomboid fossa. The cochlear part takes part in the formation of the organ of hearing.

Tongue pharyngeal nerve (item glossopharyn-geus), IX pair, is a mixed nerve that leaves the medulla oblongata with 4-5 roots and goes to the jugular foramen. Coming out of the cranial cavity, the nerve forms two nodes: the upper and lower. These nodes contain the bodies of sensory neurons. Behind the jugular foramen, the nerve goes down, goes to the root of the tongue and divides into the terminal lingual branches, which end in the mucous membrane of the dorsum of the tongue. The lateral branches extend from the glossopharyngeal nerve, which provide sensitive innervation of the mucous membrane of the tympanic cavity and auditory tube (tympanic nerve), as well as the arch of the palate and tonsil (amyloid branches), the parotid gland (small petrosal nerve), the sleepy sinus and the sleepy glomerulus ( sinus branch), motor innervation of the stylopharyngeal muscle (branch of the stylopharyngeal muscle). In addition, the branches of the glossopharyngeal nerve connect with the branches of the vagus nerve and the sympathetic trunk, forming the pharyngeal plexus.

The vagus nerve (n. Vagus), X pair, is a mixed nerve, includes sensory, motor and autonomic fibers. It is the longest of the cranial nerves. Its fibers reach the organs of the neck, chest and abdomen. There are impulses along the fibers of the vagus nerve that slow down the heart rate, dilate blood vessels, narrow the bronchi, increase intestinal peristalsis, relax the sphincters of the intestine, increase the secretion of the gastric and intestinal glands. The vagus nerve leaves the medulla oblongata in the posterior sulcus by several roots, which, when connected, form a single trunk and go to the jugular foramen. Below the jugular foramen, the nerve has two thickenings: the upper and lower nodes formed by the bodies of sensitive neurons, the peripheral processes of which go from the internal organs, the hard shell of the brain, the skin of the external auditory canal, and the central ones - to the nucleus of a single bundle of the medulla oblongata.

The vagus nerve is divided into four sections: head, cervical, thoracic, and abdominal.

The head section is located between the beginning of the nerve and the upper node, gives its branches to the hard shell of the brain, the walls of the transverse and occipital sinuses, the skin of the external auditory canal and the outer surface of the auricle.

The cervical region includes a part located between the lower node and the exit of the recurrent nerve. The branches of the cervical spine are: 1) the pharyngeal branches, innervate the mucous membrane of the pharynx, constrictor muscles, muscles of the soft palate; 2) the upper cervical cardiac branches, in? E? Those with the branches of the sympathetic trunk enter the heart plexus; 3) the superior laryngeal nerve, innervates the mucous membrane of the larynx and the root of the tongue, as well as the cricoid-shaped muscle of the larynx; 4) the recurrent laryngeal nerve, gives off branches to the trachea, esophagus, heart, innervates the mucous membrane and muscles of the larynx, except for the cricothyroid.

The thoracic region is located from the level of discharge of the recurrent laryngeal nerve to the level of the esophageal opening of the diaphragm and gives a number of branches to the heart, lungs, esophagus, participates in the formation of the cardiac, pulmonary and esophageal plexuses.

The abdominal region consists of the anterior and posterior vagus trunks. They give branches to the stomach, liver, pancreas, spleen, kidneys, intestines.

The hypoglossal nerve (item hypoglossus), XII pair, - motor, is formed by the processes of the nerve cells of the nucleus of the same name, which is located in the medulla oblongata. The nerve leaves the skull through the canal of the hypoglossal nerve of the occipital bone, innervates the muscles of the tongue and partially some muscles of the neck.

Spinal nerves

The spinal nerves (nn. Spinales) are paired, metamerically located nerve trunks, which are created by the fusion of two roots of the spinal cord - the posterior (sensory) and anterior (motor) (Fig. 3). At the level of the intervertebral foramen, they join and come out, dividing into three or four branches: anterior, posterior, meningeal white connecting branches; the latter are connected to the nodes of the sympathetic trunk. A person has 31 pairs of spinal nerves that correspond to 31 pairs of spinal cord segments (8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 pair of coccygeal nerves). Each pair of spinal nerves innervates a specific area of \u200b\u200bmuscle (myotome), skin (dermatome), and bone (sclerotome). Based on this, segmental innervation of muscles, skin and bones is distinguished.

Figure: 3. Scheme of the formation of the spinal nerve:

Spinal nerve trunk; 2 - anterior (motor) root; 3- posterior (sensitive) root; 4- root filaments; 5- spinal (sensitive) node; 6- the medial part of the posterior branch; 7- lateral part of the posterior branch; 8 - back branch; 9 - front branch; 10 - white branch; 11 - gray branch; 12 - meningeal branch.

The posterior branches of the spinal nerves innervate the deep muscles of the back, occiput, as well as the skin of the back of the head and trunk. The posterior branches of the cervical, thoracic, lumbar, sacral and coccygeal nerves are distinguished.

The posterior branch of the 1st cervical spinal nerve (C1) is called the suboccipital nerve. It innervates the large and small posterior rectus muscles of the head, the superior and inferior oblique muscles of the head and the semispinalis muscle of the head.

The posterior branch of the II cervical spinal nerve (CII) is called the greater occipital nerve, is divided into short muscle branches and a long cutaneous branch, innervates the muscles of the head and skin of the occipital region.

The anterior branches of the spinal nerves are much thicker and longer than the posterior ones. They innervate the skin, muscles of the neck, chest, abdomen, upper and lower extremities. In contrast to the posterior branches, the metameric (segmental) structure is retained by the anterior branches only of the thoracic spinal nerves. The anterior branches of the cervical, lumbar, sacral and coccygeal spinal nerves form the plexus (plexus). Allocate the cervical, brachial, lumbar, sacral and coccygeal nerve plexuses.

The cervical plexus is formed by the anterior branches of the four superior cervical (CI - CIV) spinal nerves, connected by three arcuate loops and lies on the deep muscles of the neck. The cervical plexus is connected to the accessory and hypoglossal nerves. The cervical plexus has motor (muscle), cutaneous and mixed nerves and branches. Muscular nerves innervate the trapezius, sterno-musculo-mastoid muscles, give branches to the deep muscles of the neck, and the subhyoid muscles receive innervation from the cervical loop. The cutaneous (sensory) nerves of the cervical plexus give rise to the greater auricular nerve, the lesser occipital nerve, the transverse neck nerve, and the supraclavicular nerves. The greater ear nerve innervates the skin of the auricle and the external auditory canal; small occipital nerve - the skin of the lateral part of the occipital region; the transverse nerve of the neck gives innervation to the skin of the anterior and lateral region of the neck; the supraclavicular nerves innervate the skin above and below the clavicle.

The largest nerve in the cervical plexus is the phrenic nerve. It is mixed, formed from the anterior branches of the III-V cervical spinal nerves, passes into the chest and ends in the thickness of the diaphragm.

The motor fibers of the phrenic nerve innervate the diaphragm, and the sensitive fibers - the pericardium and pleura.

The brachial plexus is formed by the anterior branches of the four lower cervical (CV - CVIII) nerves, part of the anterior branch of the I cervical (CIV) and thoracic (ThI) spinal nerves.

In the interstellar space, the front branches form three trunks - the upper, middle and lower. These trunks are divided into a number of branches and directed into the axillary fossa, where they form three bundles (lateral, medial and posterior) and surround the axillary artery on three sides. The trunks of the brachial plexus in? E? Those with their branches lying above the clavicle are called the supraclavicular part, and with the branches lying below the clavicle - the subclavian part. The branches that extend from the brachial plexus are divided into short and long. The short branches innervate mainly the bones and soft tissues of the shoulder girdle, the long ones - the free upper limb.

As part of the short branches of the brachial plexus are the dorsal nerve of the scapula - it innervates the muscle lifting the scapula, the large and small rhomboid muscles; long pectoral nerve - serratus anterior muscle; subclavian - muscle of the same name; suprascapular - supra- and abdominal muscles, the capsule of the shoulder joint; subscapularis - the eponymous and large round muscle; thoracic-dorsal - the broadest muscle of the back; lateral and medial pectoral nerves - muscles of the same name; axillary nerve - deltoid and small round muscles, the capsule of the shoulder joint, as well as the skin of the upper sections of the lateral surface of the shoulder.

The long branches of the brachial plexus originate from the lateral, medial and posterior bundles of the subclavian part of the brachial plexus.

The musculocutaneous nerve originates from the lateral bundle, gives up its branches to the brachioracoid, bilava and brachial muscles. Having given branches to the elbow joint, the nerve descends as a lateral cutaneous nerve. It innervates part of the forearm skin.

The median nerve is formed by the fusion of two radiculars from the lateral and medial bundles on the anterior surface of the axillary artery. The nerve gives the first branches to the ulnar joint, then, dropping lower, to the anterior muscles of the forearm. In the palm of the palmar aponeurosis, the median nerve is divided into terminal branches that innervate the muscles of the thumb, except for the muscle adducting the thumb of the hand. The median nerve also innervates the wrist joints, the first four fingers and part of the vermiform muscles, the skin of the dorsal and palmar surfaces.

The ulnar nerve starts from the medial bundle of the brachial plexus, goes to? E? Those with the brachial artery along the inner surface of the shoulder, where it does not give branches, then bends around the medial epicondyle of the humerus and passes to the forearm, where in the groove of the same name it goes to? E? Those with ulnar artery. On the forearm, it innervates the flexor of the ulnar hand and part of the deep flexor of the fingers. In the lower third of the forearm, the ulnar nerve divides into the dorsal and palmar branches, which then pass to the hand. On the wrist, the branches of the ulnar nerve innervate the muscle that adducts the thumb, all the interosseous muscles, two worm-like muscles, the muscles of the little finger, the skin of the palmar surface at the level of the V finger and the ulnar edge of the IV finger, the skin of the back surface at the level of V, IV and the ulnar side of the III fingers.

The medial cutaneous nerve of the shoulder leaves the medial bundle, gives the branches to the skin of the shoulder, accompanies the brachial artery, connects in the axillary fossa with the lateral branch of the II, and sometimes III intercostal nerves.

The medial cutaneous nerve of the forearm is also a branch of the medial bundle that innervates the skin of the forearm.

The radial nerve originates from the posterior bundle of the brachial plexus and is the thickest nerve. On the shoulder in the brachomuscular canal, it passes between the humerus and the heads of the three lava muscles, gives off muscle branches to this muscle and skin branches to the back of the shoulder and forearm. In the lateral groove, the cubital fossa is divided into deep and superficial branches. The deep branch innervates all the muscles of the posterior surface of the forearm (extensors), and the superficial branch goes in the groove to the radial artery, passes to the rear of the hand, where it innervates the skin of 2 1/2 fingers, starting from the thumb.

The anterior branches of the thoracic spinal nerves (ThI-ThXII), 12 pairs, run in the intercostal spaces and are called intercostal nerves. An exception is the anterior branch of the XII thoracic nerve, which passes under the XII rib and is called the hypochondrium. Intercostal nerves run in the intercostal spaces between the internal and external intercostal muscles and do not form plexuses. The six superior intercostal nerves on both sides extend to the sternum, while the five inferior costal nerves and the hypochondrium continue to the anterior abdominal wall.

The anterior branches innervate the own muscles of the chest, participate in the innervation of the muscles of the anterior abdominal wall, and give up the anterior and lateral cutaneous branches, innervating the skin of the chest and abdomen.

The lumbosacral plexus is formed by the anterior branches of the lumbar and sacral spinal nerves, which, when connected to each other, form the lumbar and sacral plexus. The connecting link between these plexuses is the lumbosacral trunk.

The lumbar plexus is formed by the anterior branches of the three upper lumbar and partially anterior branches of the XII thoracic and IV lumbar spinal nerves. It lies anterior to the transverse processes of the lumbar vertebrae in the thickness of the psoas major muscle and on the anterior surface of the quadratus lumbar muscle. From all the anterior branches of the lumbar nerves, there are short muscle branches that innervate the psoas major and minor muscles, the quadratus lumbar muscle and the inter-lumbar lateral muscles of the lower back.

The largest branches of the lumbar plexus are the femoral and obturator nerves.

The femoral nerve is formed by three roots, which first go deep into the psoas major muscle and connect at the level of the V lumbar vertebra, forming the trunk of the femoral nerve. Heading down, the femoral nerve is located in the groove between the psoas major and iliac muscles. The nerve enters the thigh through the muscle lacuna, where it gives off branches to the anterior thigh muscles and the skin of the anteromedial thigh. The longest branch of the femoral nerve is the saphenous nerve of the thigh. The last one enters with the femoral artery into the adductor canal, then enters with the descending knee artery along the medial surface of the lower leg to the foot. On its way, it innervates the skin of the knee joint, patella, partly the skin of the lower leg and foot.

The obturator nerve is the second largest branch of the lumbar plexus. From the lumbar region, the nerve descends along the medial edge of the psoas major muscle into the small pelvis, where in? E? Those with the same artery and vein goes through the obturator canal to the thigh, gives the muscle branches to the adductor thigh muscles and divides into two terminal branches: the anterior one (innervates the skin the medial surface of the thigh) and the posterior (innervates the external obturator, the greater adductor muscles, the hip joint).

In addition, larger branches extend from the lumbar plexus: 1) the ilio-hypogastric nerve - innervates the muscles and skin of the anterior abdominal wall, part of the berry region and thigh; 2) the ilio-inguinal nerve - innervates the skin of the pubis, groin, root of the penis, scrotum (skin of the labia majora); 3) the femoral-genital nerve is divided into two branches: the genital and the femoral. The first branch innervates part of the skin of the thigh, in men - the muscle that lifts the testicle, the skin of the scrotum, and the meatus; in women - the round uterine ligament and the skin of the labia majora. The femoral branch passes through the vascular lacuna to the thigh, where it innervates the skin of the inguinal ligament and the region of the femoral canal; 4) lateral cutaneous nerve of the thigh - leaves the pelvic cavity to the thigh, innervates the skin of the lateral surface of the thigh to the knee joint.

The sacral plexus is formed by the anterior branches of the upper four sacral, V lumbar and partially IV lumbar spinal nerves. The anterior branches of the latter form the lumbosacral trunk. It descends into the pelvic cavity, connects with the anterior branches of the I-IV sacral spinal nerves. The branches of the sacral plexus are divided into short and long.

The short branches of the sacral plexus include the superior and inferior gluteal nerves, the pudendal nerve, the internal obturator and piriformis, and the square muscle of the thigh. The last three nerves are motor and innervate the muscles of the same name through the piriform opening.

The superior gluteal nerve from the pelvic cavity through the epigastric foramen in the "e" those with the superior gluteal artery and vein passes between the gluteus minimus and middle muscles. It innervates the gluteal muscles, as well as the muscle that tenses the fascia lata of the thigh.

The inferior gluteal nerve leaves the pelvic cavity through the piriform opening and innervates the gluteus maximus muscle.

The long branches of the sacral plexus are represented by the posterior cutaneous nerve of the thigh, which innervates the skin of the gluteal region and partially the skin of the perineum, and the sciatic nerve.

The sciatic nerve is the largest nerve in the human body. It exits the pelvic cavity through the piriform opening, goes down and at the level of the lower third of the thigh is divided into the tibial and common peroneal nerves. They innervate the back muscle group in the thigh.

Nerve endings of PNS

Afferent nerve endings are the terminal apparatuses of the dendrites of sensitive neurons, which are ubiquitous in all human organs and provide information to the central nervous system about their condition. They perceive irritations emanating from the external environment, converting them into a nerve impulse. The mechanism of the origin of the nerve impulse is characterized by the already described phenomena of polarization and depolarization of the cytoplasmic membrane of the process of the nerve cell.

There are a number of classifications of afferent endings - depending on the specificity of the stimulus (chemoreceptors, baroreceptors, mechanoreceptors, thermoreceptors, etc.), on the structural features (free and non-free nerve endings).

Olfactory, taste, visual and auditory receptors, as well as receptors that perceive the movement of body parts relative to the direction of gravity, are called special senses. In the following chapters of this book, we will dwell only on the visual receptors.

Receptors are diverse in shape, structure, and function. In this section, our task is not to describe in detail the various receptors. We will only mention some of them in the context of describing the basic principles of structure. In this case, it is necessary to point out the differences between free and non-free nerve endings. The former are characterized by the fact that they consist only of the branching of the axial cylinders of the nerve fiber and the glial cell. In this case, they are in contact with the branches of the axial cylinder with the cells that excite them (receptors of epithelial tissues). Non-free nerve endings differ in that they contain all the components of the nerve fiber. If they are covered with a connective tissue capsule, they are called encapsulated (Vater-Pacini's little body, Meissner's tactile body, thermoreceptors of Krause's flask, Ruffini's little bodies, etc.).

The structure of muscle tissue receptors is diverse, some of which are found in the outer muscles of the eye. In this regard, we will dwell on them in more detail. The most common receptor in muscle tissue is the neuromuscular spindle (Fig. 1.5.6). This formation records the stretching of the fibers of the striated muscles. They are complex encapsulated nerve endings with both sensory and motor innervation. The number of spindles in a muscle depends on its function and the higher, the more precise movements it has. The neuromuscular spindle is located along the muscle fibers. The spindle is covered with a thin connective tissue capsule (continuation of the perineurium), inside which there are thin striated intrafusal muscle fibers of two types:

fibers with a nuclear bag - in the expanded central part of which there are accumulations of nuclei (1-4- fibers / spindle);

fibers with a nuclear chain are thinner with the arrangement of nuclei in the form of a chain in the central part (up to 10 fibers / spindle).

Sensory nerve fibers form annular helical endings on the central part of the intrafusal fibers of both types and aciniform endings at the edges of the fibers with a nuclear chain.

Motor nerve fibers are thin, form small neuromuscular synapses along the edges of the intrafusal fibers, providing their tone. peripheral nerve receptor plexus

Muscle stretch receptors are also nerve-tendon spindles (Golgi tendon organs). These are fusiform encapsulated structures with a length of about 0.5-1.0 mm. They are located in the area of \u200b\u200bthe junction of the fibers of the striated muscles with the collagen fibers of the tendons. Each spindle is formed by a capsule of flat fibrocytes (continuation of the perineurium), which encloses a group of tendon bundles braided by numerous terminal branches of nerve fibers, partially covered with lemmocytes. Excitation of the receptors occurs when the tendon is stretched during muscle contraction.

Efferent nerve endings carry information from the central nervous system to the executive organ. These are the endings of nerve fibers on muscle cells, glands, etc. A more detailed description will be given in the relevant sections. Here we will dwell only on the neuromuscular synapse (motor plaque). The motor plaque is located on the fibers of the striated muscles. It consists of the terminal branching of the axon, which forms the presynaptic part, a specialized area on the muscle fiber corresponding to the postsynaptic part, and the synaptic cleft separating them. In large muscles, one axon innervates a large number of muscle fibers, and in small muscles (external muscles of the eye), each muscle fiber or a small group of them is innervated by one axon. One motoneuron together with muscle fibers innervated by it forms a motor unit.

Conclusion

The peripheral nervous system is divided into the autonomic nervous system and the somatic nervous system.

The autonomic nervous system and the somatic nervous system act in a friendly manner. Their nerve centers, especially at the level of the brain stem and cerebral hemispheres, cannot be separated from each other; however, the peripheral regions of these two systems are completely different. The autonomic nervous system regulates the involuntary activity of internal organs, the state of internal organs and systems (it innervates the smooth muscles of blood vessels and internal organs, exocrine and endocrine glands and the parenchyma of many organs, regulates blood pressure), ensuring the maintenance of the constancy of the internal environment (homeostasis) and directed changes in dependence from the internal needs of the body and external circumstances.

Morphologically and functionally, two divisions of the autonomic nervous system are distinguished: the sympathetic and parasympathetic nervous system. The sympathetic system mobilizes the body's forces in emergency situations, increases the waste of energy resources; parasympathetic - contributes to the restoration and accumulation of energy resources.

The somatic nervous system is a part of the nervous system, which is a collection of sensory and motor neurons and their processes that belong to the central and peripheral nervous system and innervate skeletal muscles, joints, and the outer layers of the body.

The peripheral nervous system is formed by nodes (spinal, cranial and autonomic), nerves (31 pairs of spinal and 12 pairs of cranial) and nerve endings, which provide the connection of the central nervous system with all receptors and effectors of the body.

List of sources used

1. Human Anatomy: In 2 volumes, 2nd ed., Revised. and additional / Ed. M.R.Sapina. M., 1993.

Human anatomy. Mark Crocker M .: ROSMEN, 2002.

Lipchenko V. Ya., Samusev R. P. Atlas of normal human anatomy. M., 1988.

Normal human physiology. Tkachenko B.I. 2nd ed. - M .: Medicine, 2005.

Fundamentals of Human Physiology. Agadzhanyan N.A. 2nd edition, revised, Moscow: RUDN, 2001.

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Peripheral nervous system (PNS) is a conditionally distinguished part of the nervous system, the structures of which are located outside the brain and spinal cord. The peripheral nervous system includes 12 pairs of cranial nerves, their roots, sensory and autonomic ganglia located along the trunks and branches of these nerves, as well as the anterior and posterior roots of the spinal cord and 31 pairs of spinal nerves, sensory ganglia, nerve plexuses, peripheral nerve trunks trunk and extremities, right and left sympathetic trunks, autonomic plexuses, ganglia and nerves. Each nerve is composed of nerve fibers, myelinated and non-myelinated. Outside, the nerve is surrounded by a connective tissue sheath - epineurium, which includes the vessels feeding the nerve. The nerve consists of bundles, which, in turn, are covered with perineurium, and individual fibers - with endoneurium.

The conventionality of the anatomical separation of the central and peripheral nervous system is determined by the fact that the nerve fibers that make up the nerve are either axons of motor neurons located in the anterior horns of a segment of the spinal cord, or dendrites of sensitive neurons of the intervertebral ganglia (the axons of these cells are directed along the posterior roots to the spinal cord) ... 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 make up the pathways of the central nervous system (for sensitive cells).

The main function of the PNS is to provide a connection between the central nervous system and the external environment and target organs. It is carried out either by conducting nerve impulses from 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 the internal organs and systems.

In the PNS, the nerve trunks can contain motor fibers (anterior roots of the spinal cord, facial, abducens, trochlear, accessory and hypoglossal cranial nerves), sensory (posterior roots of the spinal cord, sensitive part of the trigeminal nerve, auditory nerve) or autonomic (visceral branches of the sympathetic and parasympathetic systems). The main part of the nerve trunks of the trunk and limbs is mixed (contains motor, sensory and vegetative fibers). Mixed nerves include intercostal nerves, trunks of the cervical, brachial and lumbosacral plexuses and the nerves emanating from them of the upper (radial, median, ulnar, etc.) and lower (femoral, sciatic, tibial, deep peroneal, etc.) extremities. The ratio of motor, sensory and autonomic fibers in the trunks of mixed nerves can vary significantly. The largest number of autonomic fibers contains the median and tibial nerves, as well as the vagus nerve.

There are a number of regularities in the PNS structure:

1) the nerves are paired and diverge symmetrically to the sides of the brain and spinal cord, lying along the axial line of the body;

2) nerves, like arteries, go to organs along the shortest path. If in the process of intrauterine development the organ moves, the nerve, accordingly, lengthens and follows it;

3) the nerves that innervate the muscles depart from those segments of the spinal cord that correspond to the myotomes from which these muscles originate; with their subsequent movement, the source of innervation is preserved near the zone of the bookmark;

4) nerve trunks accompany arteries, veins, lymphatic vessels, forming neurovascular bundles located on the flexor surfaces of the limbs, being protected by fascial sheaths, muscles.

Cranial nerves

12 pairs of cranial nerves branch off from the brain, of which the olfactory and optic nerves are, in essence, a reduced part of the brain, the rest of the cranial nerves resemble spinal nerves (Fig. 8.21).

Olfactory nerve (I pair) - formed by the axons of the olfactory receptor neurons. These neurons are located in the olfactory epithelium that lines the upper surface of the nasal cavity. Olfactory nerve fibers are collected in 15–20 thin olfactory nerves. The nerves pass through the openings of the ethmoid plate of the skull and end in the olfactory bulbs of the brain. Here are the cells of the second neuron. The axons of these cells as part of the olfactory pathways are directed to the primary (subcortical) olfactory centers - to the olfactory triangle, the anterior perforated space, transparent septum, thalamus. In these formations are cells of the third neuron, the axons of which are directed to the temporal lobes of their own and opposite sides, mainly to the parahippocampal gyrus. Thus, olfactory impulses from each half of the nose enter both hemispheres of the brain.

Figure: 8.21. Topography of the exit of the cranial nerves

Optic nerve (II pair) - it begins in the retina - the inner shell of the eye. There are receptors here - rods that perceive a black and white image, and cones that are responsible for color perception. The rods and cones are connected by bipolar neurocytes with neurocytes of the retinal ganglion layer. The processes of ganglionic neurons gather in a bundle in the region of the blind spot of the retina, forming the optic nerve. It pierces the choroid and sclera (intraocular part of the nerve), passes in the orbit (orbital part) to the optic canal of the skull, penetrates through it into the cranial cavity (intracanal part) and approaches the paired nerve of the other side.

At the base of the brain, anterior to the sella turcica, the optic nerves form the optic chiasm. Only the fibers extending from the inner halves of the retina of both eyes are crossed. Behind the optic chiasm, the optic tracts are formed, each of which includes fibers from the same halves of the retina of both eyes. So, fibers from the right halves of the retina get into the right optic tract, and from the left halves into the left. The optic tracts end in the primary (subcortical) visual centers - the upper mounds, thalamus and external geniculate bodies. Fibers going to the upper mounds connect the optic nerve with the oculomotor. In the external geniculate bodies and the thalamus, cells are located, the axons of which are directed to the inner surface of the occipital lobes, ending in the cerebral cortex on both sides of the groove. Above from it, the fibers end, connecting the upper half of the retina with the cortex, and downward - the fibers from the lower half of the retina.

Oculomotor nerve (III pair) - its nuclei are located in the legs of the brain under the aqueduct of the midbrain. Through the superior orbital fissure, the nerve enters the orbit, where it innervates the following muscles: the lifting upper eyelid, the upper straight (turns the eyeball upward), the inner straight (moves the eyeball inside), the lower straight (moves the eyeball downward) and the lower oblique (moves the eyeball apple up and out). The oculomotor nerve also has autonomic (parasympathetic) nuclei. The fibers emerging from them form an oculomotor root within the orbit, which is interrupted in the ciliary node and innervates the ciliary muscle, which changes the curvature of the lens, and the muscle that constricts the pupil (pupil sphincter). By changing the curvature of the lens, the eye adapts to seeing objects at close and far distances (accommodation). The sphincter of the pupil plays a protective role: when the eye is illuminated, the pupil narrows and less light enters the retina. The pupillary reflex is carried out with the participation of optic nerve fibers heading to the upper mounds (afferent part of the arch), fibers connecting the upper mounds with the nuclei of the oculomotor nerve (intercalary neuron), and parasympathetic fibers of the oculomotor nerve (efferent part of the reflex arc).

Block nerve (IV pair) - the nucleus of this nerve is located in the lining of the midbrain, at the level of the lower hillocks. The nerve leaves the brain stem through the roof of the midbrain and through the superior orbital fissure enters the orbit, where it innervates the superior oblique muscle, which turns the eyeball downward and outward.

Trigeminal nerve (V pair) - the nerve is mixed, carries out sensory and motor innervation. The trigeminal nerve nuclei are located in the brainstem. Consists of three branches: the orbital nerve, the maxillary and mandibular nerves. Of these, the first two branches are sensitive, the third contains both sensory and motor fibers.

Optic nerve provides sensitive innervation to the skin of the forehead, anterior scalp, upper eyelid, inner corner of the eye, dorsum of the nose, conjunctiva, upper part of the nasal mucosa and secretory innervation of the lacrimal gland.

Maxillary nerve leaves the cranial cavity through a round opening, innervates the skin of the lower eyelid, the lateral surface of the nose, cheeks and upper lip, the lower parts of the nasal mucosa, the upper jaw and its teeth.

Mandibular nerve leaves the cranial cavity through the oval opening, innervates the skin of the lower jaw, cheeks, lower lip, chin, lower jaw and its teeth, the mucous membrane of the cheeks, lower oral cavity, tongue, and also provides secretory innervation of the sublingual and submandibular salivary glands.

Abducens nerve (IV pair) - motor. The core is in the area of \u200b\u200bthe bridge. Further, the nerve through the superior orbital fissure is directed into the orbit and innervates the lateral rectus muscle of the eyeball, which turns it outward.

The abducens, oculomotor and trochlear nerves constitute a group of nerves that provide mobility of the eyeballs. Synchronous turns of the eyes in one direction are made due to connections between the individual nuclei of this group of nerves. Such a connection is provided by the posterior longitudinal bundle, which begins in the midbrain in the nuclei of the posterior longitudinal bundle. For the implementation of conscious eye movements, impulses come to the posterior longitudinal beam from the posterior parts of the middle frontal gyrus of the opposite hemisphere of the brain.

Facial (interfacial) nerve (VII pair) - has cores located in the bridge. The nerve exits to the base of the brain in the cerebellopontine triangle. Then the nerve bundles through the internal auditory opening enter the facial canal of the temporal bone, in which at the knee level they are divided into the facial and intermediate nerves. The intermediate nerve includes sensory fibers that carry taste impulses from the anterior two-thirds of the tongue, and parasympathetic fibers to the submandibular and sublingual salivary glands, to the lacrimal gland and the glands of the nasal mucosa and soft palate. The facial nerve leaves the skull through the styloid opening, forms a plexus in the parotid salivary gland and divides into separate branches that innervate the muscles of the face (nasal, zygomatic, circular muscles of the eye and mouth, etc.), as well as some neck muscles.

The vestibular cochlear nerve (VIII pair). It leaves the skull in the form of a cochlear and vestibular roots. The cochlear part of the nerve (actually the auditory nerve) is formed in the sensitive cochlear (spiral) node, which is located in the inner ear, in the area of \u200b\u200bthe cochlear labyrinth. The axons of the cells of the cochlear node form the cochlear (auditory) root, which, through the internal auditory opening, enters the cranial cavity and ends in the cochlear nuclei located at the back of the bridge. The fibers of the cells of the second neuron of the auditory tract, starting in the cochlear nuclei and the nuclei of the trapezius body, are sent to the primary auditory centers - the lower mounds and the medial geniculate bodies. From the medial geniculate bodies, where the cells of the third neuron of the auditory tract are located, axons are directed to the cortex of the temporal lobes of the brain. Due to the partial intersection of the fibers of the second neurons, auditory signals from each ear are sent to both temporal lobes.

The vestibular (vestibular) part of the nerve begins in the vestibular (sensory) node located at the bottom of the internal auditory canal. The dendrites of the cells of this node are directed to the receptor cells of the semicircular ducts of the inner ear. The ducts are partially filled with fluid, which irritates the receptors, moving when the position of the body or head changes. The axons of the cells of the vestibular node form the vestibular root, which is directed to the vestibular nuclei of the pons (second neuron). From the thalamus, fibers go to the cortex of the temporal lobe of the large brain, where the cortical nucleus of the vestibular analyzer is located. In addition, the nuclei of the cerebellum (tent nucleus) are connected with the nuclei of the extrapyramidal system (cerebellar-red-nuclear pathway). The main function of the vestibule is to maintain balance. In connection with the numerous connections of the nuclei of the vestibular part of the nerve, it is involved in the regulation of involuntary motor acts.

Glossopharyngeal nerve (IX pair) - mixed, has several nuclei located in the medulla oblongata. Glossopharyngeal nerve provides sensitive innervation of the mucous membrane of the upper pharynx, soft palate, posterior third of the tongue and motor innervation of the pharyngeal muscles, participating in swallowing and articulation. The secretory (parasympathetic) fibers of the glossopharyngeal nerve end in the parotid salivary gland. Taste fibers innervate the posterior third of the tongue.

Vagus nerve (X pair) - mixed, has a motor and sensory nucleus and a vegetative (parasympathetic) nucleus. The vagus nerve is the longest of all the cranial nerves, since its sphere of innervation extends from the dura mater to the sigmoid colon.

The value of the vagus nerve is very great, since it provides sensitive and vegetative (parasympathetic) innervation of all internal organs, except for the pelvic organs; a significant part of the alimentary canal (up to the sigmoid colon), heart, muscular membrane of blood vessels, trachea and lungs, glands of the mucous membrane of the esophagus, stomach and intestines, liver, pancreas, kidneys. The sensory fibers of the vagus nerve also innervate some parts of the dura mater of the brain and the external auditory canal with the auricle. The motor fibers of the vagus nerve provide voluntary movements of the muscles of the pharynx, soft palate and larynx. Thus, the vagus nerve carries out nervous regulation of such vital functions as respiration and cardiovascular activity, and also participates in the implementation of acts of swallowing and phonation.

Accessory nerve (XI pair) - motor, innervates the sternocleidomastoid and trapezius muscles.

Hyoid nerve (XII pair) - motor, innervates the muscles of the tongue.

Spinal nerves

Spinal nerves are paired nerve trunks, which are created by the fusion of two roots of the spinal cord - the posterior (sensory) and the anterior (motor) (Fig. 8.22).

At the level of the intervertebral foramen, they connect, exit and divide into four branches:

1) the front, innervating the skin and muscles of the limbs and the front surface of the body;

2) posterior, innervating the skin and muscles of the posterior surface of the body; 3) meningeal, heading to the hard shell of the spinal cord;

4) connective, containing sympathetic preganglionic fibers, following to the sympathetic nodes. The anterior branches of the spinal nerves form plexuses: cervical, brachial, lumbosacral and coccygeal.

Figure: 8.22.Spinal nerve formation diagram:

1 – the trunk of the spinal nerve; 2 – anterior (motor) root; 3 - back (sensitive) root; 4 - radicular threads; 5 - spinal (sensitive) node; 6 - the medial part of the posterior branch; 7 - lateral part of the posterior branch; 8 – back branch; nine – anterior branch; 10 - white branch; 11 - gray branch; 12 - meningeal branch

A person has 31 pairs of spinal nerves that correspond to 31 pairs of spinal cord segments (8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 pair of coccygeal nerves). Each pair of spinal nerves innervates a specific area of \u200b\u200bmuscle (myotome), skin (dermatome), and bone (sclerotome). Based on this, segmental innervation of muscles, skin and bones is distinguished.

Cervical plexus formed by the anterior branches of the I-IV cervical nerves; innervates the skin of the occiput, lateral surface of the face, supra-, subclavian and upper scapular regions, diaphragm.

Brachial plexusformed by the anterior branches of the V, VI, VII, VIII and partially I of the thoracic spinal nerves (Fig. 8.23).