The structure of the peripheral and central nervous system. The structure of the peripheral department Peripheral nerve histological structure

03.07.2020 -

The peripheral section of sound articulate speech consists of three sections.
The first section includes the apparatus that forms the voice - the larynx and vocal folds.
The larynx is a tube located between the trachea and the pharynx. It occupies the front of the neck along its median line. The larynx is an organ with three functions: protective, respiratory and vocal. In the speech system, the larynx is the organ that forms the voice.
The larynx itself borders on the esophagus, from the sides - with large vessels and nerves; the upper edge approaches the hyoid bone, the lower one passes into the trachea (windpipe).
The skeleton of the larynx is made up of cartilage. The main cartilage - cricoid - is shaped like a ring. Its narrow part is turned forward, and the so-called signet of the ring is inward towards the pharyngeal surface. Above the cricoid cartilage is the thyroid cartilage, which consists of two plates set at an angle, a notch is formed at their junction.
The thyroid cartilage in men protrudes sharply on the neck and is called the Adam's apple or Adam's apple. Behind, on the upper surface of the cricoid cartilage, there are two arytenoid cartilages, which have two processes at their base - muscular and vocal. The vocal muscle is attached to the latter. In addition, the entrance to the larynx is closed with a special cartilage - the epiglottis, reinforced with ligaments at the upper edge of the thyroid cartilage. All the cartilages of the larynx, in addition to the joints, are also held together by numerous ligaments.
The muscles of the larynx are divided into external and internal. External muscles, connecting with other parts of the skeleton, raise and lower the larynx or fix it in a certain position. These include the sternohyoid muscles, attached at their ends to the hyoid bone and sternum. These muscles fix the hyoid bone, pulling it down. The sternothyroid muscles are attached to the thyroid cartilage and the hyoid bone. These muscles shorten the distance between
hyoid bone and larynx. The cricoid anterior muscle is located between the edge of the cricoid cartilage and the lower edge of the thyroid cartilage. This muscle helps move the thyroid cartilage forward and downward.

Rice. 3. The structure of the larynx
A - profile section of the larynx and articular organs; B - diagram of these organs, taken from a profile x-ray; B - section of the larynx in profile, the vocal and cricothyroid muscles are highlighted in darker; D - diagram of the location of the oblique muscle bundles of the vocal muscle.
1 - upper lip; 2 - upper teeth; 3 - dome of the hard palate; 4 - soft palate; 5 - language; 6 - pharyngeal cavity; 7 - back wall of the pharynx; 8 - hyoid bone; 9 - epiglottis; 10 - entrance to the larynx; 11 - thyroid cartilage of the larynx; 12 - cricoid cartilage of the larynx; 13 - thyroid gland; 14 - sutured-sternum and sublingual-sternum muscles; 15 - false vocal fold; 16 - blinking into the ventricle; 17 - true vocal sklaika; 18- arytenoid cartilage covered with soft tissues; 19 - lumen of the trachea; 20 - contours of the cervical vertebrae; 21 - a membrane stretched between the hyoid bone and the thyroid cartilage; 22 - hyoid-epiglottic ligament; 23 - front end of the edge of the elastic cone (vocal fold); 24 - voice (vocal) muscle; 25 - rear end of the edge of the elastic cone (vocal fold); 26 - cricothyroid muscle; 27 -¦ scoop-cricoid joint; 28 - signet of the cricoid cartilage; 29 - fat body that fills the space between the epiglottis, hyoid bone and thyroid cartilage; 30 - left-hand cavity of the larynx.

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Fig, 4. Cartilages of the larynx
A - cartilage of the larynx on the side; B - cartilages of the larynx from behind; B - cartilages of the larynx in profile section; G - thyroid cartilage in front (above), on the side - behind (in the middle) and behind (below); D - cartilage of the larynx and hyoid bone from the side and back; E - cricoid cartilage and arytenoid cartilages; front (top), side - back (middle) n madi (bottom). I - body of the hyoid bone; 2 - sublingual shield membrane; 3 - lateral plate of the thyroid cartilage; 4 - oblique protruding line of the thyroid cartilage, which serves to attach the muscles: 5 - front, protruding forward crane of the thyroid cartilage; 6 - the lower part of the elastic cone of the larynx; 7 - thyroid cricoid joint (lower horns); 8 - annular part of the cricoid cartilage: 9 - cartilaginous rings of the trachea; 10- leaf-shaped part of the epiglottis; 11 - the posterior ends of the large horns of the hyoid bone; 12 - upper horns of the thyroid cartilage; 13 -¦ anterior end of the thickened part of the elastic cone (inner edge of the vocal fold); 14 - top scooped on a prominent cartilage; 15 - inner edge of the vocal fold; 16 - the posterior end of the thickened part of the elastic cone, attached to the vocal (vocal) process of the arytenoid cartilage; 17 - muscular process of the arytenoid cartilage; 18 - ring-scoop joint; 19 - ligament of the thyroid cricoid joint; - signet of the cricoid cartilage; 21 - membranous part of the trachea; 22 - stalk of the epiglottis; 23 - vocal (vocal) process of the arytenoid cartilage; 24 -- upper corner of the lateral plate of the thyroid cartilage; 25 - notch of the thyroid cartilage; 26 - the lower edge of the thyroid cartilage.

A - neck muscles after removal of the skin and subcutaneous fat layer; B - a group of deep muscles directly related to the larynx; more superficial muscles removed; B - squeezing the pharynx and muscles of the tongue; skull in profile section; on the left is a diagram of the action of the muscles attached to the larynx and to the hyoid bone.
] - awl-lingual muscle; 2 - posterior belly of the digastric muscle;
3 - muscle of the bottom of the mouth; 4 - anterior belly of the digastric muscle; 5 - thorn-hyoid muscle; b - muscle of the tongue, coming from the hyoid bone; 7 - middle pharyngeal constrictor; 8 - the body of the hyoid bone; 9 - shield-subhyoid muscle; 10 - lower pharyngeal compressor; 11 - upper belly of the scapular-hyoid muscle; 12 - hyoid-sternum muscle; 13 - thyroid muscle; 14 - sternocleidomastoid muscle; 15 - tendons of the sternocleidomastoid muscle; 16 - back muscle group of the neck; P - lower belly of the scapular-hyoid muscle; 18 - nasopharyngeal tonsil; 19 - nasopharynx; 20 - pharyngeal opening of the auditory (Eustachian) tube; - incision of the muscle of the upper pharyngeal constrictor; 22 - section of the muscles of the soft palate; 23 - oblique line of the thyroid cartilage; 24 - ring thyroid muscle; 25 - ring of the cricoid cartilage; 26 - tracheal rings; 27 - muscle fibers of the esophagus; 28 - muscle that raises the soft palate; 29 - sublingual-hyoid muscle; 30 - thyroid-hyoid membrane.
Rice. 5, Muscles of the neck that control the movements of the larynx.
The internal muscles of the larynx serve to perform respiratory and voice-forming activities.
These include the shield-arytenoid internal muscle, or vocal (steam), embedded in the thickness of the vocal fold. Due to the vibrations of the folds, sound is formed: sound-voice. This muscle is stretched between the inner edge of the thyroid cartilage and the vocal process of the arytenoid cartilage of the corresponding side. At rest, the vocal folds form a triangular opening for air to pass through, called the glottis.

A, B, C - the action of the cricothyroid muscles stretching the vocal folds: A - a view of the larynx in profile (the course of the fibers of the cricothyroid muscles is shown); B - diagram of the action of these muscles (solid contour - the position of the cartilage at rest; broken contour - the position as a result of the action of the ring of the thyroid muscles; the vocal fold is highlighted in black); B - diagram of the action of these muscles (top view: left - position at rest; right - as a result of the action of the cricothyroid muscles).
D, E, F - view of the entrance to the larynx from above and behind (schematically), the posterior muscle groups are dissected; D - falsetto position of the vocal cords: D - maximum opening of the glottis with a deep breath; E - phonation position of the vocal folds during chest sounding of the voice; G - scheme of muscle action in falsetto voice; 3 - diagram of the action of the muscles during a deep breath; And - a diagram of the action of the muscles in the chest voice.
I - epiglottis; 2 - hyoid bone; 3 - sublingual-thyroid membrane; 4 - the anterior edge of the thyroid cartilage; 5 - straight belly of the ring of the thyroid muscle; b - oblique abdomen of the cricothyroid muscle; 7 - attachment of the cricothyroid muscle on the anterior surface of the ring of the cricoid cartilage; 8 - cricoid-thyroid joint; 9 - anterior attachment of the vocal fold; 10 - vocal fold; 11 - posterior attachment of the vocal cord on the vocal process of the arytenoid cartilage; 12 -
signet of the cricoid cartilage; 13 - false vocal fold; 14 - blink not into the ventricle; 15 - voice
fold; 16 - top of the arytenoid cartilage; 17 - muscular process; 18 - oblique arytenoid muscle; 19 - transverse arytenoid muscle; 20 - posterior cricoarytenoid muscle; 21 - lateral cricoarytenoid muscle; 22 - external thyroid arytenoid muscle.
During speech, the vocal folds move closer together. Above the true vocal folds, there are two folds of the mucous membrane on the sides, called FALSE VOICE folds, and between the true and false vocal folds there are recesses - the so-called Morganian ventricles, the mucosa of which has many glands that moisten the vocal folds.
The respiratory activity of the larynx is provided by one pair of muscles of the cricoarytenoid posterior, which only expands the glottis, all other muscles directly or indirectly contribute to the narrowing of the glottis.
Thus, the antagonist of the cricoarytenoid posterior muscle is the cricoarytenoid lateral muscle, which brings the vocal folds together.
During the formation of sound, in addition to the tension of the vocal folds, the bases of the arytenoid cartilages come together to completely close the lumen of the glottis. This is performed by the interarytenoid transverse and oblique muscles of the larynx, which receive
participation in voting. Another muscle of the larynx - the anterior cricoid, - going from the cricoid cartilage obliquely to the back of the thyroid cartilage, with its contraction, lengthens the anteroposterior size of the larynx and thereby causes tension in the vocal folds. Originating in the larynx, the sound wave propagates up and down the airways and tissues surrounding the larynx. Experts have found that 1/10 - 1/50 of the sounds, born in the larynx, comes out of the mouth. The other part is absorbed by the internal organs and causes the tissues of the head, neck, and chest to vibrate.
The larynx is innervated (supplied) by the branches of the vagus nerve - the upper and lower laryngeal nerves, which give motor branches to the muscles of the larynx and - sensitive - to the mucosa. All internal muscles of the larynx are innervated by the inferior laryngeal nerve, with the exception of the cricothyroid muscle, which is innervated by the laryngeal nerve. It also supplies the mucous membrane of the larynx with sensitive waves.
The sound-producing, or articulatory, system belongs to the second department of the vocal apparatus. This is the oral cavity, nose and pharynx, soft palate, tongue with palatal vault, teeth, lips and lower jaw.
The sound formed during the movement of the vocal folds is amplified by the resonating cavities of the pharynx, which is a tube. It starts at the base of the skull and reaches the esophagus. Scientific research in recent years has proven that the pharyngeal cavity takes an active part in sound production, the pharyngeal resonator plays an important role in the sound of a speech voice. The upper part of the pharynx communicates with the nasal cavity through the choanae (holes) and is called the nasopharynx. The nasal cavity is divided by the nasal septum. In front, it opens with two openings (nostrils). The nasal cavity is covered with a mucous membrane, has accessory cavities: maxillary, frontal, ethmoid and main. The nasal cavity performs respiratory and resonator functions. Together with the paranasal sinuses, it takes part in the formation of the voice. Irritation by sound waves of the accessory cavities of the nose increases the tone of the vocal muscles, which intensifies the sound and improves the timbre of the speech voice.
For the correct pronunciation of speech sounds and for the timbre character of the voice, the condition of the nasal cavity and paranasal sinuses is of great importance.
French researcher R. Husson believes that vibrational sensations in the nasal cavity and paranasal sinuses irritate vast areas of the nerve endings of the trigeminal nerve and reflexively stimulate the activity of the vocal folds, and this contributes to the brightness and brilliance of the voice. The resonant participation of the nasal cavity and paranasal sinuses in the speech voice enhances its basic tone.
The organs of articulation include the oral cavity, soft palate and pharyngeal cavity, tongue with palatal vault, teeth, lips and lower jaw,
In the oral cavity, there is a hard palate on top, passing into the back. From below, the oral cavity is limited by a movable tongue, in front - by teeth, from the sides - by cheeks, behind are the pharynx and pharynx.
The pharynx is not only part of the respiratory and digestive tracts, but also an auxiliary organ involved in the formation of sound. The pharyngeal cavity is one of the sound resonators together with the nasal cavity and adnexal cavities.

A - profile incision through the right nasal cavity; B - view of nasal codes when viewed from the front of the nose; B - frontal section through the nose and the front of the skull; D - projection of the nasal cavities and adnexal cavities of the spit onto the outer integument of the eye.
1 - cranial cavity; 2 - frontal bone; 3 - frontal (frontal) sinus; 4 - opening of the channel leading from the frontal sinus to the nasal cavity; 5 - upper wall of the nasal cavity; 6 - olfactory region of the mucous membrane of the upper concha of the nose; 7 - superior nasal concha; 8 - middle turbinate; 9 - middle nasal passage; 10 - lower nasal concha; 11 - lower nasal passage; 12 - muscles of the upper lip; 13 - hard palate; 14 - soft palate; 15 - nasal septum; 16 - upper nasal passage; 17 - eye socket; 18 - sinuses of the ethmoid labyrinth; 19 - gap of the upper part of the nasal cavity; 20 - maxillary (maxillary) cavity; 21 - dental process of the upper jaw; 22 - upper large molar; 23 - sinus of the main bone; 24 - choana; 25 - pharyngeal opening of the auditory (Eustachian) tube; 26 - nasopharyngeal tonsil; 27 - nasopharynx.

It is no coincidence that many researchers establish a connection between the shape of the oropharyngeal canal and voice quality.
The hard palate takes an active part in the formation of the voice. In the works of the French scientist R. Husson, there are indications that sound waves transmit irritation through the hard palate to the second branch of the trigeminal nerve, which branches on the palatine vault. As a result, sound quality is improved: its brightness and ability to carry far.
The soft palate, or palatal curtain, also plays an important role in the development of the speech voice. With its low activity, the voice acquires a "nasal" character.
The tension of the muscles of the pharynx and soft palate (intrapharyngeal articulation) relieves the tension of the muscles of the tongue, lower jaw, larynx, improving the conditions of voice formation. In this regard, R. Yusson called the soft palate "the central voice-forming area". Elevation of the soft palate, opening of the pharyngeal cavity provide greater sound power. The training of these muscles (intrapharyngeal articulation) is carried out by special exercises.
It should be recalled that the soft palate is connected by nerve endings with many parts of the organs of speech formation. Well innervated and mucous membrane. Any upward movement of the soft palate is a stimulus for tuning all organs of voice formation.
An important organ involved in speech is the lower jaw. Thanks to its activity and mobility, vowel sounds are formed.
In the structure of the tongue, there are: tip (pointed front end), back (upper surface), edges (on both sides), root (back surface). When the tongue closes with the hard palate, the air flow is delayed or, breaking through the shutter, forms the sounds of t-d-n. If the tongue approaches the hard palate without closing with it, a prolonged noise occurs due to friction against the walls of the narrowed cavity (s-sh-z-g sounds). Delays and slowdowns in the air flow Can be created by closing the lips, the convergence of the lips, teeth (sounds b-p, m, v-f). (For details on the articulation of the lips and tongue when pronouncing vowels and consonants, see the chapter on Diction.)
An important part of the speech apparatus is the resonator-piercing system, which combines the oral and nasopharyngeal parts of the speech apparatus.
The respiratory system provides the energy needed for voice production.
The mechanism of inhalation and exhalation works "automatically", but breathing can be controlled arbitrarily. "As a result of systematic and frequent repetition of breathing exercises, they become a conditioned stimulus for the cerebral cortex and can change the nature of breathing, its rhythm, depth, etc." [‡‡‡‡‡‡‡‡‡‡].
The respiratory apparatus consists of the trachea (windpipe), bronchi with bronchioles (bronchial tree) and lung tissue, where gas exchange between air and blood takes place in the pulmonary vesicles (alveoli). The trachea branches into two bronchi, which form small branches in the lungs - bronchioles, ending, as mentioned above, with alveoli.
Thus, on the two main branches of the bronchial tree (in its appearance, the structure of the lungs is very reminiscent of a tree with branches and twigs), two lungs are formed,

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the base of the lungs lies on the diaphragm; the lateral parts of the lungs are adjacent to the walls of the chest cavity.
The lungs are covered with a double smooth and slippery membrane - the pleura. The lungs do not have their own musculature and, since they are adjacent to the inner walls of the chest and to the diaphragm, all movements of the walls of the chest cavity and diaphragm are transmitted to the lungs.
When inhaling, the inspiratory intercostal muscles and the diaphragm contract. The expansion of the chest, the descent and flattening of the dome of the diaphragm entail the expansion of the lungs and filling them with air. As soon as the muscles relax, the lungs contract due to the smooth muscles of the bronchi and the elasticity of the tissues of the lungs, but with a full breath and a sounding exhalation, inhalation and exhalation are performed voluntarily with the active participation of the inspiratory muscles and the expiratory muscles. The diaphragm is a powerful inspiratory muscle; with its participation, the lower, wider part of the lungs is filled with air. The abdominal press is its antagonist - it is a very strong exhalation muscle. The contraction of the muscle bundles of the diaphragm entails a flattening and lowering of the dome of the diaphragm, an increase in the volume of the chest cavity, expansion of the lungs and filling them with inhaled air.
When the diaphragm contracts, it presses on the organs in the abdominal cavity, the stomach protrudes slightly forward. Although the diaphragm is the main inspiratory muscle, its role during the sounding exhalation is very significant. Exhalation, as already mentioned, is provided by the abdominal muscles and intercostal muscles, which are amenable to volitional control.
According to modern data, the main energy of a sounding exhalation (singing or speech) is given by the main expiratory muscles of the chest and abdominals, but the diaphragm - the inspiratory muscle - and smooth muscles enclosed in the walls of the bronchial tree are also actively involved in this exhalation, counteracting it.
With the help of the expiratory muscles, a person can regulate the stream of exhaled air supplied to the vocal folds, can adjust the subglottic pressure necessary for a stronger or lighter sound.
The smooth muscles we are talking about are enclosed in the mucous membrane of the walls of the bronchi. They "regulate the lumen of the airways and thus make it possible to flexibly change the volume of air going to the vocal folds." Smooth muscles cannot be controlled; we can influence their work only indirectly.
In life, various types of breathing are observed, in which all the muscles of inhalation and exhalation work, only their movements are different. The "choice" of breathing in life is made and established depending on physical education from childhood.
The process of respiration in humans consists of three interrelated stages: external respiration, the transfer of gases by the blood, and tissue metabolism. The exchange between gases and blood - the essence of external respiration - takes place in the lungs and is achieved by a change of inhalation and exhalation.
At rest, a person makes 16-18 respiratory cycles per minute, inhaling approximately 500 mm3 of air per breath. This volume of air is called breathing air, but with increased breathing, another 1500 mm3 can be inhaled. This volume is called additional air. Similarly, after a normal exhalation, a person can
exhale further 1500 mm3. This volume is called reserve air. The sum of the listed volumes of air (respiratory, additional and reserve) is 3500 mm3 and is called the vital capacity of the lungs. It should be noted that sports, breathing exercises, voice development significantly increase the vitality of the lungs and have a beneficial effect on human health.
A person's breathing can be different depending on the situation. During sleep, it is rhythmic and calm, in a static position it can be rhythmic and deep. And during sudden movements - superficial. A person can co- fig. S. Diagram of the trachea and lungs knowingly control YOUR breathing.
The main regulator of respiration is the respiratory center located in the medulla oblongata. In addition, in different parts of the central nervous system there are departments that also regulate breathing in a certain way. Of great importance for the actor are conditioned reflex influences on the respiratory process, i.e., excitement before a performance or even a mental representation of a performance.
Thus, the peripheral part of the speech apparatus consists of three systems: the sound-producing system, the resonator-articulation system, and the respiratory system. And the work of the entire apparatus is achieved simultaneously by the activity of all three systems of the peripheral section under the control and regulation of the central section of speech - the brain with its pathways.
In the future, mastering diction and breathing, we will be convinced in practice of the possibility and necessity of conscious control of our speech apparatus.

Proper functioning of the nervous system on different fronts is extremely important for a full 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 referred to 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 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 on the reflex principle. A reflex is a response of an organ to a specific irritation. 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 work, etc.

Cellular mechanisms

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

membranes, or cytoplasmic membrane;
cytoplasm, or the space between the shell and the nucleus of the cell, which is filled with intracellular fluid;
mitochondria, which provide the neuron itself with energy, which they receive from glucose and oxygen;
microtubes- thin structures that perform supporting functions and help the cell 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 information transmission channels 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 the sensory perception of external stimuli (vision, hearing, tactile sensations, smell, etc.) are called sensory. Neurons that combine in networks to provide motor functions are called motor neurons. Also in the NS there are mixed neurons 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 also the basis for the statement, widespread in the literature, that “nerve cells do not regenerate”. Naturally, neurons incapable of division cannot be restored. But every second they are able to create many new neural connections to perform complex functions.

Thus, the cells are programmed to constantly create more and more 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 by 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 do not develop so rapidly.

Brain

The brain of an adult human weighs approximately 1.3-1.5 kg. Scientists have found that up to 22 years of age, 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 the connections in all the electrical devices in the world.

Researchers spend decades and tens of millions of dollars studying and trying to improve brain function.

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 and neurosurgery.

The brain is divided into the following areas:

Forebrain. The forebrain regions are usually credited with "higher" mental functions. It includes:

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

2. The midbrain includes:

The thalamus is where most of the information entering the forebrain is processed.
The hypothalamus controls information coming from the organs of the central and peripheral nervous system and the autonomic nervous system.

3. The hindbrain includes:

Spinal cord

The average length of the spinal cord of 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 brain cone. It ends with a cluster of lumbar and sacral nerves.

31 pairs of spinal nerves branch out from the spinal cord. They help 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.

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

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

Normally, its circulation should be continuous. Liquor creates a constant internal cranial pressure, performs shock-absorbing and protective functions. Analysis of the composition of the liquor is one of the simplest ways to diagnose serious diseases of the National Assembly.

What causes lesions of the central nervous system of different origins

Damage to the nervous system, depending on the period, is divided into:

Preperinatal - brain damage during fetal development.
Perinatal - when the lesion occurs during childbirth and in the first hours after birth.
Postnatal - when damage to the spinal cord or brain occurs after birth.

Depending on the nature, CNS lesions are divided into:

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, pericerebral fluid and bone tissue. However, in some cases this protection is not enough. Some injuries lead to damage to the central and peripheral nervous system. Traumatic lesions of the spinal cord are much more likely to lead to irreversible consequences. Most often, these are paralysis, moreover, degenerative (accompanied by the gradual death of neurons). The higher the damage occurred, the more extensive the paresis (decrease in muscle strength). The most common injuries are open and closed concussions.
organic damage to the central nervous system, often occur during childbirth and lead to cerebral palsy. They arise due to oxygen starvation (hypoxia). It is a consequence of prolonged childbirth or entanglement with the umbilical cord. Depending on the period of hypoxia, cerebral palsy can be of different severity: from mild to severe, which is accompanied by complex atrophy of the functions of the central and peripheral nervous system. CNS lesions after stroke are also defined as organic.
Genetically determined CNS lesions occur due to mutations in the gene chain. They are considered hereditary. The most common are Down's syndrome, Tourette's syndrome, autism (genetic and metabolic disorder), which appear immediately after birth or in the first year of life. Kensington's, Parkinson's, and Alzheimer's diseases are considered degenerative and manifest themselves in middle or old age.
Encephalopathies- most often occur as a result of brain tissue damage by pathogens (herpetic encephalopathy, meningococcal, cytomegalovirus).

The structure of the peripheral nervous system

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

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

Inflammatory processes

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

Neuralgia - these are painful inflammations in the zone of accumulation of nerve nodes, the irritation of which causes an acute reflex 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 human central and peripheral nervous system is genetically and evolutionarily determined. 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 people after a stroke eventually restore 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 methods of recovery of patients after brain injuries, methods for the development of human potential are also 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 able to develop their potential almost indefinitely.

The human nervous system is divided into central, peripheral and autonomous parts. The peripheral part of the nervous system is a collection of spinal and cranial nerves. It includes the ganglia and plexuses formed by the nerves, as well as the sensory and motor endings of the nerves. Thus, the peripheral part of the nervous system combines all the nerve formations that lie outside the spinal cord and brain. Such a combination is to a certain extent arbitrary, since the efferent fibers that make up the peripheral nerves are processes of neurons whose bodies are located in the nuclei of the spinal cord and brain. From a functional point of view, the peripheral part of the nervous system consists of conductors connecting nerve centers with receptors and working organs. The anatomy of the peripheral nerves is of great importance for the clinic, as the basis for the diagnosis and treatment of diseases and injuries of this part of the nervous system.

The structure of the nerves

Peripheral nerves consist of fibers that have a different structure and are functionally unequal. Depending on the presence or absence of the myelin sheath, the fibers are myelinated (pulply) or unmyelinated (pulpless). By diameter, myelinated nerve fibers are divided into thin (1-4 microns), medium (4-8 microns) and thick (more than 8 microns). There is a direct relationship between the thickness of the fiber and the speed of nerve impulses. In thick myelin fibers, the speed of nerve impulse conduction is approximately 80-120 m/s, in medium ones - 30-80 m/s, in thin ones - 10-30 m/s. Thick myelin fibers are predominantly motor and conductors of proprioceptive sensitivity, fibers of medium diameter conduct impulses of tactile and temperature sensitivity, and thin fibers conduct pain. Myelin-free fibers have a small diameter - 1-4 microns and conduct impulses at a speed of 1-2 m/s. They are efferent fibers of the autonomic nervous system.

Thus, according to the composition of the fibers, it is possible to give a functional characteristic of the nerve. Among the nerves of the upper limb, the median nerve has the largest content of small and medium myelinated and non-myelinated fibers, and the smallest number of them is part of the radial nerve, the ulnar nerve occupies a middle position in this respect. Therefore, when the median nerve is damaged, pain and autonomic disorders (perspiration disorders, vascular changes, trophic disorders) are especially pronounced. The ratio in the nerves of myelinated and unmyelinated, thin and thick fibers is individually variable. For example, the number of thin and medium myelin fibers in the median nerve can vary from 11 to 45% in different people.

Nerve fibers in the nerve trunk have a zigzag (sinusoidal) course, which prevents them from overstretching and creates a reserve of elongation of 12-15% of their original length at a young age and 7-8% at an older age.

Nerves have a system of their own membranes. The outer shell, epineurium, covers the nerve trunk from the outside, delimiting it from the surrounding tissues, and consists of loose, unformed connective tissue. The loose connective tissue of the epineurium fills all the gaps between individual bundles of nerve fibers. Some authors call this connective tissue the internal epineurium, in contrast to the external epineurium, which surrounds the nerve trunk from the outside.

In the epineurium, there are a large number of thick bundles of collagen fibers running mainly longitudinally, fibroblast cells, histiocytes and fat cells. When studying the sciatic nerve of humans and some animals, it was found that the epineurium consists of longitudinal, oblique and circular collagen fibers having a zigzag tortuous course with a period of 37-41 microns and an amplitude of about 4 microns. Therefore, the epineurium is a highly dynamic structure that protects nerve fibers from stretching and bending.

Type I collagen was isolated from the epineurium, the fibrils of which have a diameter of 70-85 nm. However, some authors report isolation from the optic nerve and other types of collagen, in particular III, IV, V, VI. There is no consensus on the nature of the elastic fibers of the epineurium. Some authors believe that there are no mature elastic fibers in the epineurium, but two types of fibers close to elastin were found: oxytalan and elaunin, which are located parallel to the axis of the nerve trunk. Other researchers consider them elastic fibers. Adipose tissue is an integral part of the epineurium. The sciatic nerve usually contains a significant amount of fat and differs markedly from the nerves of the upper limb.

In the study of cranial nerves and branches of the sacral plexus of adults, it was found that the thickness of the epineurium ranges from 18-30 to 650 microns, but more often it is 70-430 microns.

The epineurium is basically a feeding sheath. Blood and lymphatic vessels, vasa nervorum, pass through the epineurium, which penetrate from here into the thickness of the nerve trunk.

The next sheath, the perineurium, covers the bundles of fibers that make up the nerve. It is mechanically the most durable. Light and electron microscopy revealed that the perineurium consists of several (7-15) layers of flat cells (perineural epithelium, neurothelium) with a thickness of 0.1 to 1.0 µm, between which there are separate fibroblasts and bundles of collagen fibers. Type III collagen was isolated from the perineurium, the fibrils of which have a diameter of 50-60 nm. Thin bundles of collagen fibers are located in the perineurium without any particular order. Thin collagen fibers form a double helical system in the perineurium. Moreover, the fibers form wavy networks in the perineurium with a frequency of about 6 μm. It has been established that bundles of collagen fibers have a dense arrangement in the perineurium and are oriented both in the longitudinal and concentric directions. In the perineurium, elaunin and oxytalan fibers were found, oriented mainly longitudinally, the former being mainly localized in its superficial layer, and the latter in the deep layer.

The thickness of the perineurium in nerves with a multifascicular structure is directly dependent on the size of the bundle covered by it: around small bundles it does not exceed 3-5 microns, large bundles of nerve fibers are covered with a perineural sheath with a thickness of 12-16 to 34-70 microns. Electron microscopy data indicate that the perineurium has a corrugated, folded organization. The perineurium is of great importance in the barrier function and in ensuring the strength of the nerves.

The perineurium, penetrating into the thickness of the nerve bundle, forms there connective tissue septa 0.5–6.0 µm thick, which divide the bundle into parts. Such segmentation of the bundles is more often observed in the later periods of ontogeny.

The perineural sheaths of one nerve are connected to the perineural sheaths of neighboring nerves, and through these connections, the fibers pass from one nerve to another. If we take into account all these connections, then the peripheral nervous system of the upper or lower limb can be considered as a complex system of interconnected perineural tubes, through which the transition and exchange of nerve fibers is carried out both between bundles within one nerve and between neighboring nerves.

The innermost sheath, the endoneurium, covers individual nerve fibers with a thin connective tissue sheath. The cells and extracellular structures of the endoneurium are elongated and oriented predominantly along the course of the nerve fibers. The amount of endoneurium inside the perineural sheaths is small compared to the mass of nerve fibers. Endoneurium contains type III collagen with fibrils 30–65 nm in diameter. Opinions about the presence of elastic fibers in the endoneurium are very controversial. Some authors believe that the endoneurium does not contain elastic fibers. Others found in the endoneurium similar in properties to elastic oxytalan fibers with fibrils 10–12.5 nm in diameter, oriented mainly parallel to axons.

An electron microscopic examination of the nerves of the human upper limb revealed that individual bundles of collagen fibrils are invaginated into the thickness of Schwann cells, which also contain unmyelinated axons. Collagen bundles can be completely isolated by the cell membrane from the bulk of the endoneurium, or they can only partially penetrate into the cell, being in contact with the plasma membrane. But whatever the location of the collagen bundles, the fibrils are always in the intercellular space, and have never been seen in the intracellular space. Such close contact of Schwann cells and collagen fibrils, according to the authors, increases the resistance of nerve fibers to various tensile deformations and strengthens the "Schwann cell - unmyelinated axon" complex.

It is known that nerve fibers are grouped into separate bundles of various calibers. Different authors have different definitions of a bundle of nerve fibers, depending on the position from which these bundles are considered: from the point of view of neurosurgery and microsurgery, or from the point of view of morphology. The classical definition of a nerve bundle is a group of nerve fibers, limited from other formations of the nerve trunk by the perineural sheath. And this definition is guided by the study of morphologists. However, microscopic examination of nerves often reveals such conditions when several groups of nerve fibers adjacent to each other have not only their own perineural sheaths, but are also surrounded by a common perineurium. These groups of nerve bundles are often visible during macroscopic examination of the transverse section of the nerve during neurosurgical intervention. And these bundles are most often described in clinical studies. Due to the different understanding of the structure of the bundle, contradictions occur in the literature when describing the intratrunk structure of the same nerves. In this regard, the associations of nerve bundles, surrounded by a common perineurium, were called primary bundles, and the smaller ones, their components, were called secondary bundles.

On a transverse section of human nerves, the connective tissue membranes (epineurium, perineurium) occupy much more space (67.03-83.76%) than bundles of nerve fibers. It was shown that the amount of connective tissue depends on the number of bundles in the nerve. It is much greater in nerves with a large number of small bundles than in nerves with few large bundles.

It has been shown that the bundles in the nerve trunks can be located relatively rarely with intervals of 170-250 µm, and more often - the distance between the bundles is less than 85-170 µm.

Depending on the structure of the bundles, two extreme forms of nerves are distinguished: small-fascicular and multi-fascicular. The first is characterized by a small number of thick beams and a weak development of bonds between them. The second consists of many thin bundles with well-developed inter-bundle connections.

When the number of beams is small, the beams are large, and vice versa. Small-fascicular nerves are characterized by a relatively small thickness, the presence of a small number of large bundles, poor development of interfascicular connections, and frequent location of axons within the bundles. Multifascicular nerves are thicker and consist of a large number of small bundles; interfascicular connections are strongly developed in them; axons are loosely located in the endoneurium.

The thickness of the nerve does not reflect the number of fibers contained in it, and there are no regularities in the arrangement of fibers on the cross section of the nerve. However, it has been established that the bundles are always thinner in the center of the nerve, and vice versa on the periphery. The bundle thickness does not characterize the number of fibers contained in it.

In the structure of the nerves, a clearly defined asymmetry was established, that is, the unequal structure of the nerve trunks on the right and left sides of the body. For example, the phrenic nerve has more bundles on the left than on the right, while the vagus nerve has the opposite. In one person, the difference in the number of bundles between the right and left median nerves can vary from 0 to 13, but more often it is 1-5 bundles. The difference in the number of bundles between the median nerves of different people is 14-29 and increases with age. In the ulnar nerve in the same person, the difference between the right and left sides in the number of bundles can range from 0 to 12, but more often it is also 1-5 bundles. The difference in the number of bundles between the nerves of different people reaches 13-22.

The difference between individual subjects in the number of nerve fibers ranges from 9442 to 21371 in the median nerve, from 9542 to 12228 in the ulnar nerve. In the same person, the difference between the right and left sides varies in the median nerve from 99 to 5139, in the ulnar nerve - from 90 to 4346 fibers.

The sources of blood supply to the nerves are neighboring nearby arteries and their branches. Several arterial branches usually approach the nerve, and the intervals between the incoming vessels vary in large nerves from 2-3 to 6-7 cm, and in the sciatic nerve - up to 7-9 cm. In addition, such large nerves as the median and sciatic, have their own accompanying arteries. In nerves with a large number of bundles, the epineurium contains many blood vessels, and they have a relatively small caliber. On the contrary, in nerves with a small number of bundles, the vessels are solitary, but much larger. The arteries supplying the nerve are divided in a T-shape into ascending and descending branches in the epineurium. Within the nerves, the arteries divide to branches of the 6th order. Vessels of all orders anastomose with each other, forming intratrunk networks. These vessels play a significant role in the development of collateral circulation when large arteries are switched off. Each nerve artery is accompanied by two veins.

The lymphatic vessels of the nerves are located in the epineurium. In the perineurium, lymphatic fissures form between its layers, communicating with the lymphatic vessels of the epineurium and epineural lymphatic fissures. Thus, infection can spread along the course of the nerves. Several lymphatic vessels usually emerge from large nerve trunks.

Sheaths of nerves are innervated by branches extending from this nerve. The nerves of the nerves are mainly of sympathetic origin and are vasomotor in function.

spinal nerves

Development of the spinal nerves

The development of the spinal nerves is associated both with the development of the spinal cord and the formation of those organs that innervate the spinal nerves.

At the beginning of the 1st month of intrauterine development, the neural crests are laid on both sides of the neural tube in the embryo, which are subdivided, according to body segments, into the rudiments of the spinal ganglia. The neuroblasts located in them give rise to sensitive neurons of the spinal ganglia. On the 3rd-4th week, the latter form processes, the peripheral ends of which are directed to the corresponding dermatomes, and the central ends grow into the spinal cord, making up the posterior (dorsal) roots. Neuroblasts of the ventral (anterior) horns of the spinal cord send processes to the myotomes of "their" segments. At the 5-6th week of development, as a result of the union of the fibers of the ventral and dorsal roots, the trunk of the spinal nerve is formed.

At the 2nd month of development, the rudiments of the limbs differentiate, into which the nerve fibers of the segments corresponding to the anlage grow. In the 1st half of the 2nd month, due to the movement of metameres that form the limbs, nerve plexuses are formed. In a human embryo 10 mm long, the brachial plexus is clearly visible, which is a plate of processes of nerve cells and neuroglia, which at the level of the proximal end of the developing shoulder is divided into two: dorsal and ventral. From the dorsal plate, the posterior bundle is subsequently formed, giving rise to the axillary and radial nerves, and from the anterior, the lateral and medial bundles of the plexus.

In an embryo 15-20 mm long, all the nerve trunks of the limbs and trunk correspond to the position of the nerves in the newborn. At the same time, the formation of the nerves of the trunk and the nerves of the lower extremities takes place in a similar way, but 2 weeks later.

Relatively early (in an embryo 8-10 mm long), mesenchymal cells penetrate into the nerve trunks along with blood vessels. Mesenchymal cells divide and form the intrastem sheaths of the nerves. Myelination of nerve fibers begins from the 3rd-4th month of embryonic development and ends at the 2nd year of life. Earlier, the nerves of the upper extremities are myelinated, later - the nerves of the trunk and lower extremities.

Thus, each pair of spinal nerves connects a certain segment of the spinal cord with the corresponding segment of the body of the embryo. This connection is preserved in the further development of the embryo. Segmental innervation of the skin can be detected in an adult, it is of great importance in neurological diagnosis. Having found a sensitivity disorder in a particular part of the body, it is possible to determine which segments of the spinal cord are affected by the pathological process. The situation is different with muscle innervation. Since most large muscles are formed from the fusion of several myotomes, each of them receives innervation from several segments of the spinal cord.

1. What refers to the peripheral nervous system? How and where do the spinal nerves form and what branches do they divide into?

The peripheral nervous system is that part of the NS that connects the GM and SM with sensitive apparatuses - affectors, as well as with those organs and apparatuses that respond to external and internal stimulation with adaptive reactions (movement, secretion of glands) - effectors.

The PNS consists of:

Nerves (trunks, plexuses, roots)

Nerve ganglions

Peripheral endings

The spinal nerves are formed by the fusion of the posterior and anterior branches, which are anatomically and functionally connected to their spinal cord segments through these branches. Therefore, there are 31 pairs of s/m nerves.

The s/m nerve trunk is divided into branches:

Anterior branch

posterior branch

The meningeal branch

· White connector

2. Posterior branches of s/m nerves: their zone of innervation and peculiarities of distribution?

The posterior branch has a segmental structure. Therefore, it innervates parts of the body that have retained segmentation: deep muscles of the back, neck, skin over these areas.

The posterior branches are mixed, divided into lateral and medial branches, their diameter is less than the anterior branches. The exception is: 1). posterior branch of the I cervical s / m nerve (suboccipital nerve) - motor; 2). The posterior branch of the II cervical s / m nerve is sensitive, larger than the anterior.

3. Anterior branches of the s/m nerves: their zone of innervation and difference from the posterior ones?

The anterior branches are not segmented, they innervate parts of the body that have lost segmentation, form plexuses, the branch is mixed.

4. Why do the anterior branches of the s/m nerves form plexuses? Anterior branches of what nerves do not form them? Why?

ANSWER: plexuses are formed because the anterior branches of the s / m nerves innervate non-segmented areas. Metamerism is retained only by the anterior branches of the s/m nerves of Th2-Th11 segments, they have a segmental structure, they are called intercostal nerves.

5. What plexuses do you know? Their zone of innervation?

Plexus:

· Neck. From the anterior branches of the 4 upper cervical s/m nerves. Innervates the skin in the neck, diaphragm, neck muscles.

· Shoulder. Anterior branches of the 4 lower cervical s/m nerves. Innervates the muscles, skin of the upper extremities, superficial muscles of the chest and back.

· Lumbar plexus. Anterior branches of the lumbar nerves. Innervates the skin, muscles of the lower abdomen, thighs.

The sacral plexus. Formed by sacral nerves

6. Cranial nerves: how do they differ from the spinal nerves and into what groups according to the composition of the fibers are they divided?

CN - nerves extending from the brain. Differences from s / m nerves:

· They do not have a segmental structure, they are different in function, shape, exit points.

· Different composition of fibers.

According to the composition of the fibers, 4 groups are distinguished:

ü Sensitive (1,2,8 pairs of ChN)

ü Motor (3,4,6,11,12 pairs of ChN)

ü Mixed (5,7,9,10 pairs of CHN)

ü Having plus vegetative fibers (3,7,9,10 pairs of CHN)

7. What are peripheral nerves made of? What connective tissue membranes do they have? What is the perineural space and what is its significance?

A nerve is a part of the nervous system, which is an elongated cord formed by bundles of nerve fibers and connective tissue membranes.

They have three types of connective tissue membranes:

Endoneural - m / y with individual nerve fibers, forms separate bundles of nerve fibers;

Perineurium - surrounds several bundles of nerve fibers, is formed by two plates:

ü Visceral

ü Parietal

Epineurium - present in the largest nerves, rich in blood vessels - nourishes the nerve, provides collateral circulation.

There is a perineural space between the plates, all CNs have it, SMN is debatable, it communicates with the subarachnoid space, contains cerebrospinal fluid. Of clinical importance is the advancement of the rabies pathogen in this space to the GM and SM.

8. What is a nerve fiber? Their classification according to the caliber and speed of impulses.

A nerve fiber is a process of a nerve cell surrounded by a sheath of lemmocytes.

According to the caliber and speed of their conduct, they are divided into:

· Gr.A: thick myelin fibers up to 100 microns, v=10-120 m/s, form somatic nerves.

· Gr.B: thin myelin fibers 1-3mkm, v=3-14m/s, form pregangliol autonomic nerves.

· Gr.S: non-myelinated fibers 0.4-1.2 µm, v=0.6-2.4 m/s, form postgangliol autonomic nerves (to organs).

9. Intra-stem structure of nerves.

In addition to the fact that the composition of the nerve may include nerve fibers of different functions, surrounded by connective tissue sheaths, and having a perineural space, bundles of nerve fibers can be located in different ways. According to Sinelnikov, they distinguish:

Cable type (vegetative) - all nerve fibers run in parallel;

· Network type (somatic) - adaptive function, a special form of connections m / y with bundles of nerve fibers.

10. Patterns of location of extraorganic nerves.

The nerves are paired and diverge symmetrically with respect to the central nervous system;

Nerves reach the organs along the shortest path, with the exception of the nerves of those organs that move in the process of their development, while the nerves lengthen and change their path;

Nerves innervate the muscles from those segments that correspond to the myotomes of the muscle anlage, if the muscles move, the nerves lengthen.

Nerves accompany large arteries, veins, forming neurovascular bundles, they are located in protected places.

11. What do the types of branching of intraorgan nerves depend on? What types of them do you know in muscles with different structure and function?

Options for muscle innervation:

Main type - small branches from one large nerve;

The human nervous system is the most important organ that makes us us in every sense of the word. This is a collection of various tissues and cells (the nervous system consists not only of neurons, as many people think, but also of other special specialized bodies), which are responsible for our sensitivity, emotions, thoughts, and also for the work of every cell in our body.

Its functions as a whole are to collect information about the body or the environment using a huge number of receptors, transfer this information to special analytical or command centers, analyze the information received at a conscious or subconscious level, as well as develop decisions, transfer these decisions to internal organs or muscles with control over their execution with the help of receptors.

All functions can be conditionally divided into command or executive. Commands include information analysis, body control, and thinking. Auxiliary functions, such as control, collection and transmission of information, as well as command signals to internal organs, are the purpose of the peripheral nervous system.

Although the entire human nervous system is usually conceptually divided into two parts, the central and peripheral nervous systems are one whole, since one is impossible without the other, and a violation of the work of one immediately leads to pathological malfunctions in the work of the second, as a result, as a result, to a violation of the body or motor activity.

How the PNS works and its functions

The peripheral nervous system consists of all the plexuses and nerve endings that are outside the spinal cord, as well as the brain, which are the organs of the central nervous system.

Simply put, the peripheral nervous system is the nerves that are located on the periphery of the body outside the organs of the central nervous system, which occupy a central place.

The structure of the PNS is represented by cranial and spinal nerves, which are a kind of main conductive nerve cables that collect information from smaller, but very numerous nerves located throughout the human body, directly connecting the CNS to the organs of the body, as well as the nerves of the autonomic and somatic nervous system.

The division of the PNS into autonomic and somatic is also a bit arbitrary, it occurs in accordance with the functions performed by the nerves:

The somatic system consists of nerve fibers or endings, the task of which is to collect, deliver sensory information from receptors or sensory organs to the central nervous system, as well as to carry out motor activity, according to the signals of the central nervous system. It is represented by two types of neurons: sensory or afferent and motor - efferent. Afferent neurons are responsible for sensitivity and deliver information to the central nervous system about the environment around a person, as well as about the state of his body. Efferent, on the contrary, deliver information from the central nervous system to muscle fibers.

The autonomic nervous system regulates the activity of internal organs, exercising control over them with the help of receptors, transmitting excitatory or inhibitory signals from the central nervous system to the organ, forcing it to work or rest. It is the vegetative system, in close cooperation with the central nervous system, that provides homeostasis by regulating internal secretion, blood vessels, and many processes in the body.

The device of the vegetative department is also quite complicated and is represented by three nervous subsystems:

The sympathetic nervous system is a collection of nerves responsible for the excitation of organs and, as a result, an increase in their activity.
Parasympathetic - on the contrary, it is represented by neurons, whose function is to inhibit or calm the organs or glands to reduce their performance.
Metasympathetic consists of neurons capable of stimulating contractile activity, which are located in organs such as the heart, lungs, bladder, intestines and other hollow organs that are capable of contracting to perform their functions.

The structure of the sympathetic and parasympathetic systems is quite similar. They both obey special nuclei (sympathetic and parasympathetic, respectively) located in the spinal cord or brain, which, analyzing the information received, are activated and regulate the activity of internal organs, which are mostly responsible for processing or secretion.

Metasympathetic, however, does not have such nuclei and functions as separate complexes of microganglionic formations, the nerves that connect them, and individual nerve cells with their processes, which are completely located in the controlled organ, therefore it acts somewhat autonomously from the central nervous system. Its control points are represented by special intramural ganglia - nerve nodes that are responsible for rhythmic muscle contractions and can be regulated with the help of hormones produced by the endocrine glands.

All the nerves of the sympathetic or parasympathetic autonomic subsystem, together with the somatic ones, are connected into large main nerve fibers that lead to the spinal cord, and through it to the brain, or directly to the organs of the brain.

Diseases that affect the human peripheral nervous system:

Peripheral nerves, like all human organs, are subject to certain diseases or pathologies. Diseases of the PNS are divided into neuralgia and neuritis, which are complexes of various ailments that differ in the severity of nerve damage:

Neuralgia is a nerve disease that causes inflammation without destroying its structure or cell death.
Neuritis - inflammation or injury with the destruction of the structure of the nervous tissue of varying severity.

Neuritis can occur immediately due to a negative effect on the nerve of any origin or develop from neglected neuralgia, when, due to the lack of treatment, the inflammatory process caused the onset of neuron death.

Also, all the ailments that can affect the peripheral nerves are divided according to the topographic-anatomical feature, or, more simply, according to the place of occurrence:

Mononeuritis is a disease of one nerve.
Polyneuritis is a disease of several.
Multineuritis is a disease of many nerves.
Plexitis is an inflammation of the nerve plexuses.
Funiculitis is an inflammation of the nerve cords - the channels of the spinal cord that conduct nerve impulses, along which information moves from the peripheral nerves to the central nervous system and vice versa.
Radiculitis is an inflammation of the roots of peripheral nerves, with the help of which they are attached to the spinal cord.

They are also distinguished by etiology - the reason that caused neuralgia or neuritis:

Infectious (viral or bacterial).
Allergic.
Infectious-allergic.
Toxic
Traumatic.
Compression-ischemic - diseases due to compression of the nerve (various pinchings).
Dysmetabolic nature, when they are caused by a metabolic disorder (vitamin deficiency. Production of some substance, etc.)
Discirculatory - due to circulatory disorders.
Idiopathic character - i.e. hereditary.

Disorders of the peripheral nervous system

When the organs of the central nervous system are affected, people feel a change in mental activity or a disruption in the functioning of internal organs, as the controlling or command centers send the wrong signals.

When a breakdown of peripheral nerves occurs, the person's consciousness usually does not suffer. It can only be noted possible incorrect sensations from the senses, when a person seems to have a different taste, smell, or tactile touches, goosebumps, etc. way. Also, problems can arise with problems with the vestibular nerve, with a bilateral lesion of which a person can lose orientation in space.

Usually, lesions of peripheral neurons lead, first of all, to pain or loss of sensitivity (tactile, gustatory, visual, etc.). Then there is a cessation of the work of the organs for which they were responsible (muscle paralysis, cardiac arrest, inability to swallow, etc.) or a malfunction due to incorrect signals that were distorted during passage through the damaged tissue (paresis, when muscle tone is lost , sweating, increased salivation).

Serious damage to the peripheral nervous system can lead to disability or even death. But can the PNS recover?

Everyone knows that the central nervous system is not able to regenerate its tissues through cell division, since neurons in humans stop dividing after reaching a certain age. The same applies to the peripheral nervous system: its neurons are also unable to multiply, but can be replenished to a small extent by stem cells.

However, people who underwent surgery, and temporarily lost the sensitivity of the skin of the incision area, noticed that after some long time it was restored. Many people think that new nerves have sprouted instead of cut old ones, but in fact this is not the case. It is not new nerves that grow, but old nerve cells form new processes, and then throw them into an uncontrolled area. These processes can be with receptors at the ends or intertwined, forming new nerve connections, and, consequently, new nerves.

The restoration of the nerves of the peripheral system occurs in the same way as the restoration of the central nervous system through the formation of new nerve connections and the redistribution of responsibilities between neurons. Such restoration replenishes the lost functions often only partially, and also does not do without incidents. With severe damage to any nerves, one neuron may not belong to one muscle, as it should, but to several with the help of new processes. Sometimes these processes penetrate rather illogically, when, with an arbitrary contraction of one muscle, an involuntary contraction of another occurs. Such a phenomenon quite often occurs with neglected neuritis of the trigeminal nerve, when, while eating, a person begins to involuntarily cry (crocodile tears syndrome) or his facial expressions are disturbed.

As an option for restoring peripheral fibers, a neurosurgical intervention is possible, when they are simply sutured. In addition, a new method is being developed using foreign stem cells.