Departments The autonomic (autonomic) nervous system. Functions of the autonomic nervous system

All organs of our body, all physiological functions, as a rule, have stable automatism and the ability to self-regulate. Self-regulation is based on the principle of “feedback”: any change in function, and even more so going beyond the limits of permissible fluctuations (for example, too much increase in blood pressure or its decrease) causes excitation of the corresponding parts of the nervous system, which send impulses-orders that normalize the activity of the organ or systems. This is carried out by the so-called vegetative, or autonomous, nervous system.

The autonomic nervous system regulates the activity of blood vessels, heart, respiratory organs, digestion, urination, endocrine glands. In addition, it regulates the nutrition of the central nervous system itself (the brain and spinal cord) and skeletal muscles.

The activity of the autonomic nervous system is subordinated to the centers located in the hypothalamus, and they, in turn, are controlled by the cerebral cortex.

The autonomic nervous system is conditionally divided into sympathetic and parasympathetic systems (or departments). The first mobilizes the body's resources in various situations that require a quick response. At this time, the activity of the digestive organs, which is not essential for the moment, is inhibited (blood supply, secretion and motility of the stomach and intestines decrease) and attack and defense reactions are activated. The content of adrenaline and glucose in the blood increases, which improves the nutrition of the muscles of the heart, brain and skeletal muscles (adrenaline dilates the blood vessels of these organs, and more blood rich in glucose enters them). At the same time, the activity of the heart quickens and intensifies, blood pressure rises, its clotting accelerates (which prevents the danger of blood loss), a frightening or cowardly facial expression appears - the palpebral fissures and pupils expand.

A feature of the reactions of the sympathetic division of the autonomic nervous system is their redundancy (i.e., the mobilization of an excess amount of reserve forces) and advanced development - they turn on at the very first danger signals.

However, if the state of excitation (and even more so overexcitation) of the sympathetic nervous system is repeated very often and persists for a long time, then instead of a beneficial effect on the body, it can be harmful. So, with frequently repeated excitation of the sympathetic department, the release of hormones into the blood, which narrow the vessels of the internal organs, increases. As a result, blood pressure rises.

The constant repetition of such situations can cause the development of hypertension, angina and other pathological conditions.

Therefore, many scientists consider the initial stage of hypertension as an expression of increased reactivity of the sympathetic nervous system. The connection between the overexcitation of this system and the development of hypertension, heart failure and even myocardial infarction has been confirmed in animal experiments.

The parasympathetic nervous system is activated in conditions of rest, relaxation, and a comfortable state. At this time, the movements of the stomach and intestines increase, the secretion of digestive juices, the heart works in a rarer rhythm, the rest period of the heart muscle increases, its blood supply improves, the vessels of the internal organs expand, due to which blood flow to them increases, blood pressure decreases.

Overexcitation of the parasympathetic nervous system is accompanied by various unpleasant sensations in the stomach and intestines, and even sometimes contributes to the development of gastric and duodenal ulcers. By the way, night pains in people suffering from peptic ulcer disease are explained by increased parasympathetic activity during sleep and inhibition of the sympathetic nervous system. This is also associated with the frequent occurrence of asthma attacks during sleep.

In experiments on monkeys, it was found that stimulation of various parts of the parasympathetic system by electric current naturally caused the appearance of ulcers on the mucous membrane of the stomach or duodenum in experimental animals. The clinical picture of the experimental peptic ulcer was similar to the typical manifestations of this disease in humans. After transection of the vagus (parasympathetic) nerve, the pathological influence of the stimulus disappeared.

With frequent and prolonged activation of both parts of the autonomic nervous system (sympathetic and parasympathetic), a combination of two pathological processes may occur: a steady increase in blood pressure (hypertension) and peptic ulcer.

Under normal conditions, in a healthy person, the sympathetic and parasympathetic divisions are in a state of balanced dynamic equilibrium, which is characterized by a slight predominance of sympathetic influences. Each of them is sensitive to the slightest changes in the environment and reacts quickly to them. The balance of the divisions of the autonomic nervous system is also reflected in the mood of a person, which colors all mental phenomena. Violations of this balance not only "spoil" the mood, but also cause various painful symptoms, such as spasms of the stomach and intestines, changes in the rhythm of cardiac activity, headache, nausea, dizziness.

In the implementation of vegetative reactions, the tone of the cortex of the frontal lobes of the brain is of great importance. When it decreases, caused, for example, by mental overwork, nerve impulses coming from the internal organs can be recorded in the mind as a signal of trouble. A person mistakenly evaluates such sensations as painful (heaviness in the stomach, discomfort in the region of the heart, etc.). With a normal tone of the cerebral cortex, impulses from the internal organs do not reach the higher parts of the brain and are not reflected in consciousness.

Under certain conditions, mental processes occurring in the cerebral cortex can have an active influence on the activity of internal organs. This was convincingly demonstrated by experiments with the development of conditioned reflex changes in the activity of the heart, the tone of blood vessels, respiration, digestion, excretion, and even blood composition. The fundamental possibility of arbitrarily changing autonomic functions was also established by observing the effects of hypnotic suggestion and self-hypnosis. Trained in a certain way, people can cause expansion or constriction of blood vessels (i.e., lower or increase blood pressure), increase urination, sweat, change metabolic rate by 20-30%, reduce heart rate or increase heart rate. However, all these self-actions are by no means indifferent to the organism. For example, cases are known when an inept voluntary influence on the activity of the heart manifested itself so sharply that a person lost consciousness. And therefore, the use of such a system of self-regulation as autogenic training should be accompanied by an awareness of the seriousness and effectiveness of the method of influencing the body with a word.

The processes in the internal organs, in turn, are reflected in the state of the brain and mental activity. Everyone knows changes in mood and mental performance before and after eating, the impact on the psyche of a reduced or increased metabolism. So, with a sharp decrease in metabolism, mental lethargy appears; an increase in metabolism is usually accompanied by an acceleration of mental reactions. With full health, characterized by the dynamic constancy of the work of all physiological systems, such a mutual influence of the cerebral cortex and the vegetative sphere is expressed by a feeling of a comfortable state, inner peace. This feeling disappears not only with certain disturbances in the internal environment of the body, for example, with various diseases, but also during the period of “pre-disease”, as a result of malnutrition, hypothermia, as well as various negative emotions - fear, anger, etc.

The study of the structure and functions of the brain made it possible to understand the causes of many diseases, to remove the mystery of the “miracles of recovery” from therapeutic suggestions in a state of hypnosis and self-hypnosis, to see the unlimited possibilities of cognition and self-knowledge of the brain, the limits of which are still not known. Indeed, in the cerebral cortex, as already mentioned, there are an average of 12 billion nerve cells, each of which encloses many processes from other brain cells. This creates the prerequisites for the formation of a huge number of connections between them and is an inexhaustible reserve of brain activity. But usually a person uses a very small part of this reserve.

It has been established that the brain of primitive people was potentially capable of performing much more complex functions than was necessary only for the survival of the individual. This property of the brain is called super redundancy. Thanks to this, as well as articulate speech, people can reach the heights of knowledge and pass it on to their descendants. The superabundance of the brain is far from exhausted even in modern man, and this is the key to the future development of his mental and physical abilities.

AUTONOMIC NERVOUS SYSTEM, part of the nervous system of vertebrates and humans, which regulates the activity of the organs of blood circulation, digestion, respiration, excretion, reproduction, metabolism and growth of the body; plays a leading role in maintaining homeostasis and adaptive reactions of the organism. The term "autonomic nervous system" was introduced in 1800 by M. Bisha, based on the fact that this part of the nervous system regulates processes that are characteristic not only of animals, but also of other organisms. Since the functions of the autonomic nervous system cannot be voluntarily caused or consciously terminated, the English physiologist J. Langley called it autonomous.

Anatomically and functionally, the autonomic nervous system is divided into the sympathetic nervous system (SNS), parasympathetic nervous system (PNS) and metasympathetic nervous system (MNS). In the SNS and PNS, efferent pathways emanating from the central nervous system (CNS) consist of two series-connected neurons. The cell bodies of the first neurons of the SNS lie in the thoracic and lumbar spinal cord, and the PNS - in the middle and medulla oblongata and in the sacral spinal cord. The second neurons (located outside the CNS) form ganglia near the spine, on the way to the organs (in the SNS), not far from the innervated organ or directly in it (in the PNS). The influence of the PNS on the work of many organs (heart, kidneys, etc.) is provided mainly through the vagus nerve. The nerve fibers of the autonomic nervous system are characterized by a low speed of signal conduction compared to the CNS. In the ganglia of the SNS and PNS, acetylcholine serves as a signal transmitter; it is also secreted from the postganglionic fibers of the PNS. In the SNS, this role is played by norepinephrine (rarely, acetylcholine). Other mediators may be used along with norepinephrine and acetylcholine.

The influence of the SNS and PNS on organs is often opposite. Thus, the activation of the SNS leads to the expansion of the bronchi, an increase in the strength and frequency of contractions of the heart, the expansion of the pupils, the inhibition of the peristalsis of the gastrointestinal tract and the secretion of digestive juices, the relaxation of the bladder, and the activation of the PNS causes the opposite effect. The SNS and PNS have tonic (maintained) activity: for example, an increase in the heart rate can be achieved by activation of the SNS or inhibition of the PNS. The effects may have the same direction, but differ in the features of manifestation: for example, PNS causes abundant secretion of liquid saliva, and SNS causes moderate secretion of viscous saliva. For a number of functions, the effects of the two departments may be summed up; thus, the PNS stimulates erection, and the SNS stimulates ejaculation. Some functions are regulated only by the PNS (for example, the work of the lacrimal glands) or the SNS (the breakdown of glycogen and fats, an increase in the efficiency of skeletal muscles, the work of the sweat glands). In many organs (except the brain, tongue, digestive glands, genital organs), vascular tone is also maintained only by the SNS. In general, the PNS is responsible for restoring the resources expended by the body, and the SNS ensures its adaptation to extreme conditions.

MNS (the term was introduced by A. D. Nozdrachev) innervates internal organs endowed with their own motor activity: stomach and intestines (Auerbach's plexus, Meissner's plexus), bladder, heart, etc. It has its own sensitive and intercalary neurons and is extremely diverse in terms of a set of mediators . After damage to the MHC, organs lose the ability to coordinate rhythmic contractions.

The work of the Ministry of Taxation is autonomous, but is regulated by the SNS and the PNS. The activity of the SNS and PNS is controlled by nerve centers (respiratory, cardiovascular, salivary, etc.), which are located in the medulla oblongata. At this level, the work of the centers can change reflexively and independently of others. These reflexes are under the control of the hypothalamus. Signals coming from the cerebral cortex also change the activity of the autonomic nervous system, which ensures a holistic response of the body to stimuli.

Parts of the nervous system that coordinate the work of internal organs in invertebrates are called visceral. Their elements are found in lower worms as formations associated with the intestinal tube, and starting with nemerteans and annelids, independent ganglia are formed. In arthropods, the system of ganglia and nerve trunks leading to the heart and stomach muscles is quite clearly identified, but only in insects are the head and tail sections separated, sometimes compared with the PNS of vertebrates, and the trunk section, comparable to the SNS.

Lit .: Nozdrachev AD Physiology of the autonomic nervous system. L., 1983.

O. L. Vinogradova, O. S. Tarasova.

The autonomic division of the nervous system is that part of the single nervous system that regulates metabolism, the work of internal organs, the heart, blood vessels and glands of external and internal secretion, smooth muscles. At the same time, it should be borne in mind that the function of regulating the entire vital activity of the body is carried out by the central nervous system and especially its higher department - the cerebral cortex.

This part of the nervous system received the name "vegetative" due to the fact that it is related to the work of those organs that perform the functions inherent in plants (from the Latin vegitas - plant), that is, respiration, nutrition, excretion, reproduction, exchange substances. In addition, this system is sometimes not quite aptly called "autonomous". This name emphasizes that although the autonomic nervous system is subordinate to the cerebral cortex, unlike the peripheral nervous system, it does not depend on the will of the animal. Indeed, if the movement of the body is in the power of the will of the animal, then the movement of the internal organs, the work of the glands are performed independently of its will.

The function of the autonomic nervous system is also based on the reflex arc. However, its sensitive links have not yet been studied enough.

Rice. 292. Scheme of the structure of a segment of the vegetative part of the nervous system in connection with the spinal cord:

/ - gray and white medulla of the spinal cord; 3 - motor fibers; 4 - ventral root; 5 - preganglionic fiber of the neuron; 5 - white connecting branch; 7 - node of the boundary shaft; 8 - border sympathetic trunk; 9 - intramural ganglia in the intestinal wall; 10 - lateral column of the gray medulla; // - sensitive fibers; 12 - dorsal root of the spinal node; 13 - mixed spinal nerve; 14 - gray connecting branch; 15 - postganglionic fiber of n-ney-ron to the vessels; 16 - prevertebral ganglion; 17 - postganglionic fiber of the neuron to the insides; X - vagus.

The autonomic nervous system is divided into two parts - sympathetic and parasympathetic. Each internal organ is innervated by both. However, they often act differently on the body. If one intensifies the work of the body, then the other, on the contrary, slows it down. Thanks to their action, the organ perfectly adapts to the demands of the moment. So, with an increase in the amount of roughage, intestinal peristalsis increases, with a decrease in them, it weakens; when the illumination increases, the pupil contracts, when it gets darker, it expands, etc. Only when both seemingly mutually exclusive influences are preserved, the organ functions normally*.

In the autonomic part of the nervous system (both sympathetic and parasympathetic parts) there are (Fig. 292): 1) centers located in different parts of the central nervous system and representing a collection

Rice. 293. Scheme of the autonomic nervous system of cattle

(according to I.P. Osipov):

A - centers of the parasympathetic part of the nervous system (in the sacral spinal cord); B - centers of the sympathetic part of the nervous system (in the lumbar-thoracic region of the spinal cord); B - spinal cord; centers of the parasympathetic part of the nervous system in the medulla oblongata; G - the center of the vagus nerve; D - salivary and lacrimal centers; E - the center of the parasympathetic part of the nervous system (in the midbrain); 1 - parasympathetic pathways to the organs of the pelvic cavity and the caudal part of the abdominal cavity; 2 - border sympathetic trunk; 3 - caudal mesenteric node; 4 - vertebral ganglia; 5 - semilunar node (solar plexus center); 6 - small splanchnic nerve; 7 - large splanchnic nerve; 8 - vagus nerve; 9 -- stellate node; 10 - middle cervical knot; 11 - vertebral nerve; 12 - vagosympathy-kus; 13-cranial cervical node; 14 - rectum; 15 - vagina and uterus; 16-bladder; 17 - ovary; 18 - jejunum; 19 - kidney with adrenal gland; 20 - spleen; 21 - duodenum; 22 - pancreas; 23-stomach; 24 - liver; 25 - diaphragm; 26 - lungs; 27 - heart; 28 - salivary glands; 29 - lacrimal gland; 30 - sphincter of the pupil.

Lenia of the bodies of nerve cells; 2) preganglionic fibers (4), which are a complex of neurites of the nerve cells mentioned above; 3) ganglia (7), into which preganglionic fibers enter and where they enter into a synaptic connection with the dendrites of ganglion cells; 4) postganglionic fibers (15, /7), which are neurites of ganglion cells and are already directed to the innervated organ; 5) nerve plexuses (Fig. 293). Preganglionic and postganglionic fibers differ not only topographically, but also in structure. Preganglionic fibers are usually covered with myelin sheath and therefore have a white color. Postganglionic fibers are devoid of this sheath, gray in color, and slowly conduct excitation.

Sympathetic part of the autonomic nervous system

The sympathetic part of the autonomic part of the nervous system in different classes of chordates is developed differently^. So, no elements of the system were found in the lancelet. In cyclostomes, it is represented by two rows of ganglia segmentally located on the sides of the aorta, which are not connected to each other, but are in connection with the spinal nerves on one side and with the viscera and heart on the other side. In the internal organs, sympathetic branches form plexuses that unite the ganglia, with ganglion cells. The same cells are found in the walls of the body of animals along the motor and sensory somatic nerves. In bony fish, sympathetic paired ganglia are also located in the head region. In this case, all trunk ganglia on each side of the animal's body are connected to each other into two long paired strands, forming two sympathetic border trunks. The ganglia that make up this trunk are connected on the one hand to the spinal nerves, on the other hand to the viscera, forming plexuses in them. The fibers that go from the spinal cord to the vertebral ganglia are called pre-ganglionic, and from the ganglia to the organs - postgangliopar. The right and left border sympathetic trunks do not connect with each other.

In higher vertebrates, starting with anurans, the caudal, sometimes sacral, and even lumbar sections of the border sympathetic trunk are less developed and partially or completely connected in the caudal section. It is assumed that in the process of phylogenesis in vertebrates, individual nerve cells are evicted from the spinal ganglia, which are located in the subbodies of the vertebrae and form the vertebral sympathetic ganglia. They are also connected with each other, with the spinal cord and with the organs innervated by them, forming plexuses.

The sympathetic system of mammals is composed of: 1) centers, which are bodies of nerve cells located in the central nervous system; 2) preganglionic fibers, which are processes of the cells of the center of the sympathetic nervous system, which reach 3) numerous ganglia of the sympathetic nervous system, and 4) postganglionic fibers, starting from the bodies of ganglion cells and heading to different organs and tissues (Fig. 293-1 -13).

1. The center of the sympathetic part of the autonomic nervous system is located in the lateral horns of the entire thoracic and the first two or four segments of the lumbar spinal cord (B).

2. The ganglia of the sympathetic nervous system are very numerous and form a system of right and left border sympathetic trunks, located on the sides of the vertebral bodies and called vertebral (2), and a system of unpaired prevertebral ganglia lying below the spinal column, near the abdominal aorta.

In the border sympathetic trunks, cervical, thoracic, lumbar, sacral and caudal ganglia are distinguished. In this regard, although the center of the sympathetic part of the autonomic nervous system is located only in the thoracic and partly in the lumbar spinal cord, however, the border sympathetic trunk extends along the entire body of the animal and is divided into the head, cervical, thoracic, lumbar, sacral and caudal regions. In the cervical region of the sympathetic nervous system, cattle and pigs have three cervical ganglia - cranial, middle and caudal: the horse does not have a middle ganglion. In the thoracic region, the number of ganglia in most cases corresponds to the number of vertebrae, with the first thoracic ganglion often merging with the last cervical ganglion to form the stellate ganglion (9). There are also paired ganglia in the lumbar, sacral, and caudal regions of the border sympathetic trunk (I.P. Osipov).

The system of prevertebral ganglia includes: an unpaired semilunar ganglion, which in turn consists of one cranial mesenteric and two celiac ganglia fused together, and a caudal mesenteric ganglion. The semilunar ganglion lies on the aorta and covers with its ends the base of the celiac and cranial mesenteric arteries, which depart from the aorta. The caudal mesenteric ganglion is located at the base of the caudal mesenteric artery. They are located in the abdominal cavity.

3. Preganglionic sympathetic fibers, which are neurites of the cells of the lateral horns of the thoracic and partially lumbar spinal cord, connect the center of the sympathetic nervous system with the ganglia. Preganglionic fibers exit the spinal cord as part of the ventral root of the spinal nerve (Fig. 292-5). Having left the spinal canal together with the spinal nerve, they soon separate from it under the beast, enter into a symplastic connection with the dendrites ™™ "™" ™ "* others simply pass through them, heading back or forward to the next ganglion, and end already in it or go even further. Thanks to it, the vertebral sympathetic ganglia are connected with each other into the border trunk of the sympathetic nervous system, which in cattle reaches the seventh caudal vertebra. caudal sheTn^Gy- in the area around the last cervical vertebra, then the pr^anglionary fibers connecting them have a significant length of the spine. Combining together with the vagus nerve, they form p. vagosympaticus.

Finally, part of the preganglionic fibers is directed to the caudal and, having passed through the last few thoracic ganglia, the FOR ^ V "^ n th intracerebral nerve - n. splanchnicus major (Fig. 293-7) and the small Gutren Uno Rstny Gnerv _n. splanchicus minor (6). The first of them in cattle "and pigs it is formed" due to neurites of the cells of the lateral ^ horns VT XII a v of the horse VI-XV thoracic segments, and the second - due to three last ^ ogn ^ passing "t" through the diaphragm from the thoracic bands ™-abdominal and Most of the preganglionic fibers of these nerves terminate in the semilunar ganglion, but a large number of them seem to go to the caudal mesenteric glia, into which the preganglionic fibers also enter from the lumbar infundibulum and nJJ RH. , is the cervical part of the borderline sym-PaTIGgoloveS™gaanglionic fibers depart from the cranial cervical

The nervous system gives only gray connecting branches to the spinal nerves of their site.

Numerous postganglionic fibers depart from the semilunar ganglion, which, before entering the organ innervated by them, branch, intertwine with each other, forming numerous plexuses: gastric, hepatic, splenic, cranial mesenteric, renal and adrenal. The four splanchnic nerves entering the semilunar ganglion (right and left large and right and left small) and the numerous postganglionic nerve fibers emerging from it diverge from the semilunar ganglion along the radii, like rays from the disk of the sun, which gave reason to call this part of the sympathetic system the solar plexus - plexus Solaris (Fig. 293-5).

From the caudal mesenteric ganglion, postganglionic fibers are sent to the caudal part of the intestine, as well as to the organs of the pelvic cavity. These fibers also form a number of plexuses: caudal mesenteric, internal testis (ovarian), form the hypogastric nerve with the hypogastric plexus, the thyroid plexus of the penis, cystic, hemorrhoidal and a number of others.

Parasympathetic part of the autonomic nervous system

The parasympathetic part of the vegetative part of the nervous system differs from the sympathetic part of the same part mainly by the location of its centers, less anatomical isolation, in many cases by a different effect on the same organ, aimed, however, at ensuring its better performance, as well as that its ganglia are either very close to the centers, or, conversely, at a very distant distance from them. Functionally, they are the same and ensure the functioning of the body in connection with its various states.

The parasympathetic part of the autonomic part of the nervous system consists of the central part, preganglionic fibers, ganglia and postganglionic fibers (Fig. 293-L, D, E, E).

The center of the parasympathetic system is located in the middle and medulla oblongata, as well as in the lateral horns of the sacral spinal cord. In this regard, it is divided into head and sacral sections; while the first, in turn, is divided into midbrain and medulla oblongata.

In the mid-brain area, the center is located in the region of the oral tubercles of the quadrigemina, from where the preganglionic parasympathetic fibers exit as part of the oculomotor nerve and reach the ciliary ganglion. From it, postganglionic parasympathetic (and sympathetic) fibers joining them pass through other nerves to the eyeball and branch out in the sphincter of the pupil and in the ciliary muscle, consisting of smooth muscle tissue. Sympathetic nerves provide pupil dilation; parasympathetic, on the contrary, narrowing it (E).

The medulla oblongata of the parasympathetic nervous system has several centers. In accordance with this, four directions, or paths, are noted in it: lacrimal, two salivary and visceral (to the insides) (D, E).

1. The tear tract has a center at the bottom of the fourth cerebral ventricle, from where the preganglionic parasympathetic fibers enter the facial nerve and reach the sphenopalatine node, which lies in the fossa of the same name. From this node, the postganglionic parasympathetic (and sympathetic) fibers that join them are sent along other cranial nerves to the lacrimal glands, and partly to the glands of the mucous membrane of the palate and nasal cavity. 2. The oral salivary pathway begins at the bottom of the fourth cerebral ventricle. The preganglionic parasympathetic fibers of this pathway exit the skull as part of the facial nerve and enter the sublingual, or submandibular, node located medially from the sublingual salivary gland. From this node, postganglionic parasympathetic fibers (together with sympathetic) are sent to the submandibular and sublingual salivary glands of their sides. 3. The center of the second salivary tract lies somewhat more aboral than the first. The preganglionic parasympathetic fibers of this path, as part of the glossopharyngeal nerve, reach the ear node located near the torn opening. From the ear node, parasympathetic postganglionic fibers go to the parotid salivary gland and the buccal and labial glands. 4. The visceral path, that is, for the viscera, provides motor and secretory activity of the internal organs of the chest and abdominal cavity. The center of this path is the nuclei of the vagus nerve, located in the bottom of the rhomboid fossa of the medulla oblongata. Preganglionic fibers, which are the neurites of the cells of these nuclei, form the bulk of the vagus nerve. However, it also contains somatic (non-vegetative) fibers.

From the cranial cavity, the vagus nerve - p. vagus - exits through the posterior edge of the torn hole and goes along the neck through the chest cavity into the abdominal cavity. The vagus nerve is conditionally divided into cervical, thoracic and abdominal parts. Its cervical part (8) is combined with the cervical part of the sympathetic border trunk into one common trunk - the vagosympatheticus. The thoracic part of the vagus nerve separates from the sympathetic border trunk, gives off the recurrent nerve (somatic fibers) to the pharynx and larynx, as well as a number of parasympathetic branches to various organs located in the chest cavity, and divides into dorsal and ventral branches along the esophagus. Numerous branches of the vagus nerve in the chest cavity, uniting with sympathetic fibers, form various plexuses that innervate the esophagus, heart, blood vessels, trachea, lungs, etc. Later, the dorsal branches of the vagus nerve of the right and left sides merge into one dorsal esophageal trunk, and ventral - into the ventral esophageal trunk, which pass through the diaphragm into the abdominal cavity. The abdominal part of the vagus nerve can be traced anatomically to the solar plexus, and its physiological action extends to all organs innervated from the solar plexus. The preganglionic fibers that make up the vagus terminate in ganglia embedded within the wall of the innervated organ. For their position, these ganglia are called intramural. They are found only histologically. The postganglionic fibers of the vagus are short and terminate near the ganglion, innervating the glandular tissue and smooth muscles of the organs: the stomach, liver, pancreas, all the intestines of the small intestine and most of the intestines of the large intestine.

In the sacral (sacral) part of the parasympathetic part of the autonomic nervous system, the center lies in the lateral horns of the sacral spinal cord. The preganglionic parasympathetic fibers of this area exit with the first three or second or fourth pairs of sacral nerves. After leaving the spinal canal, the parasympathetic fibers are separated from the spinal nerves and form the pelvic nerve - n. pelvicus, or n. engesh, which innervates the end of the colon, rectum, bladder and genitals.

The autonomic nervous system (ANS) is an autonomous part responsible for the functioning of absolutely all internal organs of a person, adequate metabolism, blood circulation and adaptation to constantly changing environmental conditions.

The anatomy of the ANS is quite complex and confusing; to facilitate its study, it is customary to divide it into several departments, first of all, it is necessary to consider the central and peripheral.

The central part is represented by the nuclei of some, which lie in the thickness of the tissues of the brain and spinal cord. In the midbrain there are centers responsible for the diameter of the pupil, the work of the eye, in the nervous tissue of the medulla oblongata and sacral there are fibers responsible for the work of the gastrointestinal tract, heart, liver and other organs.

A special place in the central section is occupied by the hypothalamus and the limbic structure. The first has three groups of nuclei, is responsible for the work of all endocrine and external secretion glands, regulates the act of breathing, the tone of arteries and veins. The limbic structure is involved in behavioral responses, with the help of it a person is able to make plans, dream and be awake during the day.

The peripheral section consists of autonomic nerves, plexuses, endings, a sympathetic trunk and parasympathetic ganglia. The first three parts bring the electrical impulse to the desired target, that is, to a certain part of the body, organ, and so on. The next two parts are included in two fundamentally different, but very important divisions of the ANS: parasympathetic and sympathetic.

• The parasympathetic autonomic nervous system transmits its impulses through the production of a special mediator - acetylcholine. Consists of long presynaptic and short postsynaptic fibers. It does not innervate the brain, the smooth muscle wall of the blood vessels, with the exception of some organs, the skeletal muscles, and practically all the sense organs. This department is responsible for the secretion of saliva into the oral cavity, a decrease in heart rate and blood pressure indicators, provides bronchospasm, peristalsis of the small and large intestines, and other necessary functions.
• The sympathetic autonomic nervous system consists of sympathetic chains, ganglia, connected and located on either side of the spine, as well as the celiac plexus and mesenteric nodes. Adrenal hormones are involved in the transmission: adrenaline and norepinephrine, therefore, it is activated in stressful situations. It mainly enhances the work of internal organs, but there is an exception, which are discussed below.

Functions

The work of almost every cell in the body and normalizes metabolic processes. If we consider the influence of each of the departments, then we can form a whole list of systems that affect the production of certain biologically active substances. The functions of the autonomic system are also divided into two large parts.

With the functioning of the sympathetic part:

1. From the side of the CCC: the heartbeat quickens, the pressure on the walls of the arteries increases due to a decrease in their lumen, the strength and release of blood into the main vessels (aorta and pulmonary artery) increase;
2. On the part of the respiratory system: it increases the frequency of breathing, expands the bronchi, thereby providing increased ventilation of the lungs and greater delivery of oxygen to organ systems, the secretion of the glands of the ciliated epithelium decreases;
3. From the side of the bladder: the ducts and the wall of the bladder itself relaxes;
4. On the part of the digestive system: the peristalsis of the small and large intestines decreases, the tone of the sphincters of the gastrointestinal tract and the secretion of the accessory glands of the stomach increase, the gallbladder itself and its ducts relax;
5. From the glands of external and internal secretion: the production of both enzymes and hormones increases, respectively, the metabolism is accelerated - protein synthesis, energy supply and other vital processes;
6. On the part of the sense organs: it mainly affects the eye, or rather, dilates the pupil, reduces the oculomotor muscles.

When the parasympathetic department is turned on:

1. From the side of the CCC: a decrease in heart rate up to cardiac arrest, the strength of contractions also decreases, the conduction of impulses slows down, atrioventricular blockade may develop, blood pressure drops;
2. On the part of the respiratory system: the tone of the smooth muscle wall of the bronchi increases, bronchospasm is formed, the secretion of glands secreted from goblet cells increases, the respiratory rate becomes less;
3. From the sensory organs: pupil diameter decreases, oculomotor muscles relax;
4. On the part of the digestive system: the peristalsis of the gastrointestinal tract increases, the tone of the sphincters decreases, the production of secretions from the main and parietal glands of the stomach increases, the gallbladder ducts and the organ itself contract;
5. From the glands of external and internal secretion: metabolism decreases, glycogen is synthesized in the liver to a greater extent, the concentration of glucose in the blood falls, the amount of secreted hormones also falls;
6. From the side of the bladder: the wall of the bladder contracts, the sphincter relaxes, which facilitates urination.

Differences from the somatic nervous system

(SNS) is arbitrary, that is, controlled by human consciousness. It is responsible for the contraction of striated muscle tissue, that is, mainly for the motor activity of the musculoskeletal system.

Vegetative NS differs sharply in structure and function. With regard to anatomy, the differences mainly relate to the reflex arcs and the place where the nerve fibers originate. The reflex arc itself in both parts consists of three parts: sensitive, intercalary and executive. In most cases, the sensitive link in both types is common, but the executive link has a different localization. In the case of the ANS, it is located outside the central nervous system, that is, in close proximity to the target organ. The arc of the SNS ends in the spinal cord, in its gray matter.

The nerve fibers of the ANS are smaller in diameter, they are not fully covered with a myelin sheath, they have a lower speed of electrical impulse conduction, therefore, a more powerful irritating factor is needed to conduct it. The axons of neurons are short and interrupted in the ganglia. The SNS is the exact opposite: the fibers are larger, all myelinated, the speed is higher, the axons are continuous and longer.

As for neurotransmitters, the biologically active substance of the somatic nervous system is only acetylcholine, which regulates the transmission of all impulses. The autonomic nervous system is very diverse, its mediators are norepinephrine and adrenaline, histamine, acetylcholine, serotonin, adenosine triphosphoric acid and others.

Formation during embryogenesis

The nervous system itself is formed from the ectoderm. In the third week of fetal growth, sympathetic trunks and nodes begin to form from neuroblasts migrating from the neural tube, at the same time they tend to localize future internal organs. Initially, sympathetic nodes are formed in the intestinal wall, then - in the heart tube. All processes end by the end of the seventh week of embryo development. initially appears in the face from the same neuroblasts that have separated from the head end of the neural tube.

At the same time, the vegetative centers of the spinal cord develop, they originate from sympathoblasts. Here, embryonic development begins from the thoracic to the lumbar segment.

The formation of higher nervous activity begins with the formation of the brain, and this is the second month of embryogenesis.

It is during this period that the limbic system, the hippocampus, the hypothalamus and the cerebral cortex acquire the necessary structure.

Further differentiation of nerve fibers occurs in conjunction with the growth of the internal organs and body of the fetus.

Possible deviations in work

Since people, especially in the modern world, are always subject to stress, the human nervous system ceases to adequately regulate the processes of the body, and the state of health is sharply reduced.

The most common disorders include autonomic dysfunction syndrome, formerly called vegetative-vascular dystonia. Its symptoms can be indigestion, a change in blood pressure up or down, increased ventilation of the lungs due to an increase in respiratory rate, or, conversely, a subjective feeling of lack of air. Behavior changes dramatically, as the autonomic nervous system is responsible for mood, perception of the surrounding world and adaptation.

The patient may become apathetic, suspicious, his behavior and views on certain things will change. The main problem in diagnosis is the similarity of the clinical picture of autonomic dysfunction with other serious pathologies of the gastrointestinal tract, heart, blood vessels, endocrine glands and other organs. Treatment is mainly carried out by a neurologist, psychotherapist and psychiatrist, they build the correct therapy regimen and partly help the patient cope with emotional experiences.

The nervous system of the human body and animals is divided into two types - this is the somatic and autonomic nervous system. The nervous somatic system is under the conscious control of a person and can obey him, and the autonomic nervous system, on the contrary, does not obey a person, and is under his unconscious control.

The somatic system performs a dual function. She receives information about the environment through the senses - such as the eyes, which have special receptors. Signals from these receptors enter the central nervous system through sensitive channels. Also, the somatic system sends signals from the central nervous system through the motor channels to causing these movements.

The system is a department of the nervous system that regulates vascular tone, lymphatic and work and internal secretion, as well as all internal organs.

The ANS maintains the constancy of the environment (homeostasis) in the body at the right level and performs. Thanks to the autonomic nervous system, the functions of the internal organs and the entire human body adapt to changes in the external environment and affect its mental and physical activity.

The autonomic nervous system is divided into two sections: peripheral and central. The peripheral section includes nerves, nerve fibers and branches that emerge from the centers of the system in the spinal cord and brain, plexuses of these nerve fibers and nerves, ganglia (vegetative nodes), sympathetic trunks, which consist of ganglia with connecting nerves and branches, as well as vegetative nodes of the parasympathetic division of the ANS.

The central department of the ANS is divided into segmental (lower) and suprasegmental (higher) vegetative centers. Segmental centers are located both in the spinal cord and in the brain. The suprasegmental centers of the ANS are concentrated only in the cerebral cortex, mainly in the parietal and frontal lobes, olfactory brain, cerebellum, hypothalamus, subcortical structures, etc.

The autonomic nervous system has two types - parasympathetic and sympathetic. They differ in the location of their effector and central neurons and also in their influence on the functioning of the innervated structures.

In the parasympathetic nervous system, the central neurons are located in the spinal cord, in its sacral segments (segments 2-4), but most of these neurons are located in the brain stem and depart from it with mixed cranial nerves. The central neurons are located in the spinal cord in the gray matter from the eighth cervical segment to two or three lumbar. Sympathetic nerves depart only from the spinal cord along the ventral (anterior) roots as part of the spinal nerves. Thanks to the parasympathetic nerves serving the work of the bronchi, they narrow, the sympathetic nerves, on the contrary, expand the bronchi.

The autonomic nervous system is responsible for the implementation of all vital functions and processes in the body, and is also partially responsible for reproduction, which is very important in procreation. The ANS also ensures the normal regulation of heart rate, body temperature, blood pressure, monitors the activity of various biochemical processes in the body. At the slightest change in internal or external conditions, the vegetative system launches compensatory and control mechanisms that at the right time change the tone of blood vessels, control breathing, and activate mental activity.