And its morphological features. Phylo- and ontogeny of autonomous

Historical excursion. Concept of the autonomic nervous system

nervous system. Sympathetic, parasympathetic and meta-

Historical excursion. In the process of progressive evolution and in connection with the specialization of parts of the body, two divisions were distinguished in the initially unified nervous system - vegetative and animal.

The emergence of the concepts of “vegetative” and “animal” is associated with the ideas of the French scientist M. Biche (19th century) about the presence of plant (vegetative) and animal (animal) functions in the body. TO vegetative include the functions of nutrition, respiration, excretion, reproduction and circulation of fluids; these functions are characteristic of both animal and plant organisms. TO animalistic functions include voluntary muscle contractions and the functions of special sense organs (vision, hearing, smell, taste and touch), which are characteristic exclusively of animal organisms. Thus, the formation of the animal nervous apparatus is associated with the development of sensory organs and voluntary (striated) muscles, and the vegetative one is associated with evolutionary changes in internal organs, blood vessels and glands. Later, the famous physiologist Claude Bernard postulated a new feature of the autonomic nervous system, turning it into a system of involuntary innervation. The sign of involuntary behavior turned out to be fruitful in many ways. He allowed the English physiologist W. Gaskell to draw attention to the presence in the body of two types of muscle tissue, subject to “voluntary” and “involuntary” innervation, respectively. The innervation of the muscles of blood vessels, skin formations, and internal organs turned out to be involuntary.

Gaskell also showed the existence of a peculiar chemical sensitivity of muscles, some of which react by contracting to the use of adrenaline. This allowed him to divide the involuntary nervous system into sympathetic (adrenal) and parasympathetic (nervous system of the viscera). Subsequently, his compatriot John Langley established the difference in the design of voluntary and involuntary innervation. He showed that voluntary somatic innervation is carried out in a single-neuron way - the body of the nerve cell lies in the central nervous system, and its process lies on the periphery, reaching the executive organ (skeletal muscle). At the same time, the path of involuntary autonomic innervation is represented by two neurons, the first of which is located in the central nervous system, the second in the peripheral ganglion. Langley called this involuntary part of the n/s autonomous, thereby emphasizing its much greater independence from the central nervous system.

The special role of the autonomous nervous system in the body was substantiated by Academician L.A. Orbeli. Data from his school showed that autonomic (sympathetic) innervation affects the functional state of all organs and tissues, including parts of the central nervous system. Thus, the basic principle of its functioning in the body was formulated - adaptive-trophic character influence exerted.

The function of autonomous n/s is not autonomous, although it is not controlled by our consciousness; it is subordinate to the spinal cord, cerebellum, hypothalamus, basal nuclei of the telencephalon and the higher parts of the n/s - the cerebral cortex.

According to the international anatomical nomenclature, the term vegetative n/s has now been replaced with autonomous n/s, and the term animal n/s with somatic one. TO autonomic nervous system(systema nervosum autonomicum) refers to a complex of central and peripheral nervous structures, the main function of which is V. Canon’s maintenance of homeostasis, i.e. constancy of the internal environment of the body (V. Canon, 1939). Homeostatic mechanisms ensure the body's independence from changing environmental conditions. Autonomous n/s is not controlled by consciousness, but with somatic n/s it functions in collaboration. Thus, the autonomous n/s controls the functions of internal organs, blood vessels and glands, and also exercises an adaptive and trophic effect on all organs of animals.

The concept of the autonomic nervous system. The nervous system is one, but it is conventionally divided according to the functional principle and zones of innervation into somatic and autonomic.

Somatic n/s It innervates mainly the body (soma), namely the musculoskeletal system, the skin, and connects the body with the external environment through the sensory organs.

Autonomous (vegetative) n/s innervates internal organs (heart, lungs, stomach, intestines..), glands, blood vessels, heart, and also regulates metabolic processes and maintains the constancy of the internal environment of the body.

Anatomically, the autonomous nervous system of higher vertebrates is represented by autonomic centers located in the spinal cord and brain, autonomic ganglia and nerve fibers.

The basis of the activity of the nervous system is made up of reflexes, the morphological substrate of which is reflex arcs, which are a chain of sensory (afferent), transmission (intercalary) and motor (efferent) neurons. Afferent neurons of the autonomic and somatic reflex arcs are located in the sensory spinal and cranial ganglia. Consequently, these ganglia are common to somatic and autonomic n/s. Interneurons of the autonomic n/s, unlike somatic ones, are located in separate foci in the spinal cord and brain and form vegetative (autonomous) centers.

As for the efferent (motor) neurons, there are significant differences: somatic efferent neurons are concentrated in the central nervous system, and autonomous efferent neurons moved outside the central nervous system and formed autonomic (autonomous) ganglia – ganglia autonomica . Thus, in the autonomic nervous system, the efferent path of the reflex arc is represented by two neurons. The first neuron is an interneuron, which is located in the autonomic centers, and the second is an efferent neuron, which lies in the autonomic ganglia. The processes of these neurons are sent to organs as part of the autonomic or mixed nerves.

Features of the autonomic nervous system. Unlike somatic n/s, autonomic one has a number of features:

1. Vegetative centers, or nuclei, are located focally, i.e. in certain areas of the middle, medulla oblongata, and spinal cord.

2. The path to the innervated organ necessarily goes through ganglion, therefore, the nerve pathways of the autonomic n/s are formed by two neurons. The first neuron is located in the autonomic centers, its fibers end in the ganglion and are called preganglionic. The second neuron is located in the ganglion, the fibers extending from it are called postganglionic. They go to the innervated organ. (Center-preganglionic fiber-Ganglion-postganglionic fiber-Organ).

3. Formation along the nerve fibers autonomic plexuses– plexus autonomici around blood vessels, at the hilum of an organ or inside its wall.

4. Preservation of primitive structural features - this is a smaller caliber of nerve fibers, the absence of a myelin sheath in a large part of the fibers. Therefore, vegetative fibers are mainly unmyelinated and consist of several nerve fibers (3-20), surrounded by a common connective tissue sheath

5. Lack of strict segmental structure, which is characteristic of the somatic nervous system.

6. The presence of its own sensitive (affrent) neurons and, as a consequence, the formation of simple reflex arcs of local significance.

Classification of the autonomic nervous system. The autonomic nervous system is usually divided into sympathetic (pars sympathica) and parasympathetic (pars parasympathica) divisions. This division has historical roots and is associated with the research of J. Langley, who first proposed dividing the autonomic nervous system into sympathetic and parasympathetic sections; as for the nerve plexuses of the intestinal wall, J. Langley identified them separately and called them the “enteric system.” Subsequently, Academician A.D. Nozdrachev, continuing research in this area, proposed replacing the term “enteric system” with the metasympathetic department. Thus, the autonomic nervous system, according to recent research, is divided into three divisions: sympathetic, parasympathetic and metasympathetic(“enteral”), which have certain functional and structural features (Human Physiology, edited by R. Schmidt, G. Tevs, 1996, vol. 2).

In turn, the development of parts of the autonomous n/s probably proceeded in parallel, which explains the presence of a single effector unit (Center-Ganglion-Organ) in each of them. The path from the center to the innervated organ lies through the ganglia. In the process of evolution, this link has developed special properties characteristic of each of these parts. The sympathetic and parasympathetic departments have reflex arcs with the formation of their own centers in the spinal cord and brain. In the metasympathetic part, the sensory apparatus became isolated, its own “pacemaker” and effector neuron with its own mediator support emerged. In other words, in the metasympathetic part of the n/s their own vegetative centers appeared, located directly in the walls of the executive organs.

Phylo- and ontogeny of the autonomic nervous system. In phylogenesis, an autonomous n/s goes through a complex development path. In invertebrates (annelids - annelids), the nerve elements associated with the intestinal tube are isolated and independent ganglia are formed. In arthropods, the autonomic ganglia and the nerve trunks coming from them are differentiated into sympathetic (trunk) and parasympathetic (cranial and caudal). For the first time, the appearance of metasympathetic n/s is observed in cyclostomes (lamreys) and cartilaginous fish (sharks, rays) along the sympathetic plexuses of the digestive canal. In the series of bony fishes, a paired sympathetic trunk is formed with connections characteristic of higher vertebrates. In reptiles, in addition, intramural plexuses are formed in the internal organs. And in birds, preganglionic fibers leave the spinal cord as part of the ventral roots.

In embryogenesis, the source of cells is autonomous n.s. in mammals there is a ganglion plate, which is divided into areas that subsequently give rise to sympathetic and parasympathetic n.s. Their peripheral part, as well as the metasympathetic n.s. are formed as a result of the migration of neuroblasts into the walls of internal organs.

Depending on the location of the autonomic centers and ganglia, as well as the nature of the influence on the functions of the innervated organs, the autonomic n/s is divided into three parts: sympathetic n/s - Pars sympatica (from the Greek sympathies - sensitive, susceptible to influence), parasympathetic n/s - Pars parasympatica (from the Greek para- near, at) and metasympathetic n/s - Pars metasympatica.

Sympathetic part of the nervous system

The sympathetic nerve is trophic in its main functions. It causes an increase in metabolic processes, an increase in cardiac activity, an increase in blood pressure, increased respiration, an increase in the supply of O 2 to the muscles, and at the same time a weakening of the secretory and motor functions of the digestive tract. The sympathetic nervous system affects the muscular layer (smooth myocytes) of blood vessels, which is why it is also called “vascular”.

The sympathetic nervous system is divided in structure into a central part, located in the spinal cord (thoracolumbar), and a peripheral part, including ganglia, nerve fibers and their plexuses.

Sympathetic centers- the intermediolateral nuclei are located in the lateral (lateral) horns of the thoracolumbar spinal cord (from the 1st thoracic to the 4th lumbar). Axons from the sympathetic centers through the intervertebral foramina exit the spinal cord along the ventral roots in the form of white connecting branches (preganglionic fibers - rr. communicantes albi) and go to the sympathetic ganglia.

Sympathetic ganglia are mainly located along the spinal column (paravertebral) and along large blood vessels.

Paravertebral ganglia are located metamerically on both sides of the spinal column and form the basis of the sympathetic trunk (ganglia truci sympathici). The sympathetic trunk (trucus sypathicus) is paired (right and left) and is divided into cervical, thoracic, lumbar, sacral and caudal sections.

The number of sympathetic ganglia, as a rule, corresponds to the number of neurosegments, but there are exceptions, since they can merge with each other, for example, in the cervical region there are only three of them (cranial, middle, caudal); in the thoracic region, the first three, merging with each other and with the caudal cervical region, form the cervicothoracic (stellate) ganglion; in the caudal region in the region of the 2-4 caudal vertebrae, both trunks, right and left, are connected into an unpaired caudal ganglion from which sympathetic fibers can reach the 7-9 caudal vertebrae.

Preganglionic fibers enter the ganglia of the sympathetic trunk along the white branches - these are the axons of neurons of the sympathetic centers. Postganglionic fibers depart from the ganglia of the sympathetic trunk: one part of the fibers in the form of gray connecting branches (rr. communicantes grisei) goes as part of all spinal nerves to the smooth muscles of the blood vessels of the body, and the other part goes as part of special nerves, having a certain course and zone of innervation . These include the external and internal carotid nerves, the jugular nerve, the vertebral nerve, the cardiac, pulmonary, esophageal, thoracic, and aortic nerves, which run along the vessels, form the corresponding sympathetic plexuses and innervate them.

Ganglia, along large blood vessels, are located at a considerable distance from the spinal cord in the perivascular plexuses. These include the ganglia of the abdominal and pelvic cavities. Preganglionic fibers often enter them in transit through the sympathetic trunk and form such large nerves as the greater and lesser splanchnic nerves and the hypogastric nerve. These nerves enter the ganglia of the abdominal and pelvic cavities (celiac, cranial and caudal mesenteric, pelvic) and from them the postganglionic fibers are sent to the organs independently or together with the vessels, branching into them, forming plexuses of the same name. One of the largest autonomic plexuses of the abdominal cavity is the abdominal aortic plexus, located on the aorta and continuing on its branch. The largest and most important in the composition of the abdominal aortic plexus is the “solar” plexus (celiac), which is located around the trunk of the same name. The solar plexus includes 2 celiac and cranial mesenteric ganglia, which can unite into the semilunar ganglion. The right and left large and small splanchnic nerves and lumbar splanchnic nerves approach the solar plexus; fibers of the vagus nerve, as well as sensory fibers of the right phrenic nerve, pass through its nodes in transit. Thus, nerves containing postganglionic sympathetic fibers and preganglionic parasympathetic fibers depart from the solar plexus ganglia, which, together with the vessels, are sent to the organs. Located around the organs, the nerves form the so-called vascular (periarterial) autonomic plexuses (splenic, hepatic, gastric, cranial mesenteric). From the caudal mesenteric ganglion, located on the artery of the same name, postganglionic fibers emerge, from which the hypogastric nerve, testicular or ovarian plexus are formed. Postganglionic fibers from the hypogastric ganglia form a continuation of the hypogastric nerve and the hypogastric or pelvic plexus located on the mesorectum or broad uterine ligament.

Thus, the peripheral part of the sympathetic nervous system is represented by ganglia, nerve trunks and plexuses.

Parasympathetic part of the nervous system

Parasympathetic n/s plays a mainly protective role. When it is excited, the pupil constricts in strong light, cardiac activity slows down during sleep and rest, blood pressure decreases, the bronchi contract, and at the same time, the function of the digestive tract increases. It affects the muscular membranes (smooth myocytes) of the glands and internal organs.

The general organization of the parasympathetic n/s is similar to the sympathetic one. It also distinguishes central and peripheral formations; the transmission of excitation to the executive organ is mainly carried out along a two-neuron pathway: the preganglionic neuron is located in the gray matter of the brain; postganglionic is located far to the periphery.

The parasympathetic nervous system has a number of features:

1. Its central structures are located in 3 different, widely separated areas of the brain, separated not only from each other, but also from the sympathetic centers;

2. Parasympathetic fibers innervate, as a rule, only certain areas of the body, which are also supplied with sympathetic, and others with metasympathetic innervation.

3. Preganglionic parasympathetic fibers are usually longer than postganglionic fibers. For sympathetic fibers it is often the other way around.

4. The transmission of nerve impulses from preganglionic fibers to the ganglion is carried out, both in the sympathetic and parasympathetic, by a mediator, i.e. chemical substance - acetylcholine. But the transmission of nerve impulses from postganglionic fibers to effectors is carried out by different mediators: in the sympathetic nervous system - adrenaline and norepinephrine, and in the parasympathetic system - also acetylcholine.

Parasympathetic n/s also consists of central and peripheral. The central structures of the parasympathetic nervous system are located in the midbrain and medulla oblongata, as well as in the sacral part of the spinal cord. The peripheral section is represented by nerve ganglia, which are located near or inside the innervated organs (extra and intramural), trunks and plexuses.

Central structures parasympathetic nerves are located in the midbrain, medulla oblongata and in the sacral spinal cord.

Midbrain center forms parasympathetic pathways into the sphincter of the pupil and into the ciliary muscle. This center is represented by the Edinger-Westphal nucleus, lying near the oral tubercles of the quadrigeminal at the bottom of the cerebral aqueduct medial from the nucleus of the oculomotor nerve (midbrain cap). Preganglionic fibers follow in the ventral branch of the oculomotor nerve (3rd) to the ciliary ganglion, which lies on this nerve. Short ciliary nerves emerge from the ganglion; they contain postganglionic parasympathetic, sympathetic (from the cranial cervical ganglion) and sensory fibers.

Medulla oblongata center contain nuclei: lacrimal, two salivary, as well as motor and secretory nuclei of the vagus nerve for internal organs. Preganglionic fibers to the lacrimal, salivary glands and other formations of the head leave the center as part of the facial (7th) and glossopharyngeal (9th) cranial nerves and end on the effector neurons of the pterygopalatine, auricular, mandibular (hyoid) ganglia. From the ganglia, postganglionic fibers in the facial and trigeminal cranial nerves go to the innervated organs.

Parasympathetic fibers of the vagus nerve originate in the caudal nucleus, which is located lateral to the nucleus of the glossopharyngeal nerve. The axons of the neurons of this nucleus form preganglinar fibers, which, as part of the vagus, follow to the ganglia of the periorgan and intraorgan plexuses. Postganglionic fibers carry out parasympathetic innervation of the smooth muscles and glands of the neck, chest and abdominal cavity. The vagus nerve has a mixed function. Its afferent fibers go from the mucous membrane of the digestive tract (starting from the pharynx) and the respiratory tract (starting from the larynx) to the neurons of the proximal (jugular) and distal (nodular) ganglia. Efferent somatic fibers are directed to the striated (striated) muscles of the pharynx and larynx. Efferent parasympathetic - into the unstriated (smooth) muscles of the digestive tract (starting from the esophagus), trachea and bronchi, and into the heart muscle. Efferent secreting fibers of the vagus branch in the glands of the digestive and respiratory tract. The vagus nerve follows along the trachea into the chest cavity together with the cervical part of the sympathetic trunk, forming a common trunk - the vagosympaticus, and, dorsomedially accompanying the common carotid artery. At the entrance to the chest cavity, the vagus separates, enters the mediastinum and is directed along the esophagus into the abdominal cavity.

Sacral section represented by centers located in the lateral horns of the three sacral segments of the spinal cord. From here, as part of the pelvic nerves, preganglionic parasympathetic fibers are sent to the parasympathetic pelvic ganglia, which form plexuses (rectal, prostate, uterine, vaginal, etc.) located near organs or in their walls. Postganglionic fibers provide parasympathetic innervation to the smooth muscles and glands of the pelvic cavity.

Thus, postganglionic parasympathetic fibers innervate the eye muscles, lacrimal and salivary glands, muscles and glands of the digestive tract, trachea, larynx, lungs, atria, excretory and genital organs. Unlike the sympathetic, the parasympathetic does not innervate the smooth muscle of blood vessels, with the exception of the genital arteries.

The autonomic nervous system is the part of the nervous system that innervates internal organs and blood vessels, that is, organs that contain smooth muscle elements and glandular epithelium. The state of the autonomic nervous system directly affects the metabolism in the organs. This part of the nervous system gets its name, vegetative, from the Latin name “vegetatio” - excitement or “vegeto” - to revive, strengthen, animate. Sometimes the name vegetative is translated as plant.

Bichat used this term for the first time in 1880. He divided all organs into plant and animal. The organs of plant life perform functions inherent in all living things, including plants: respiration, nutrition, growth, excretion, reproduction. Animal organs, according to Bish, are organs that provide the function of movement in space. These include: the musculoskeletal system, from which active movement is provided by muscles.

Autonomic organs act involuntarily, automatically and without rest. Animal organs act voluntarily and require rest.

The English physiologist Langley first began to call the autonomic nervous system autonomic at the end of the 19th century. He separated it completely from the nervous system. This opinion was wrong. This system does not have absolute autonomy and is under the control of the central nervous system. A major role in the further development of knowledge about the autonomic nervous system was played by domestic scientists, especially neurohistologists, who, using the method of selective staining of nerve elements with methylene blue, obtained a lot of new data on the structure of individual parts of the autonomic nervous system. Of particular importance are the works of Lavrentiev, Kolosov, I.F. Ivanov, Dolgo-Saburov, Melman and others.

The distinction of the autonomic (autonomic) nervous system is due to certain features of its structure.

focal localization of vegetative nuclei in the central nervous system;

accumulation of bodies of effective neurons in the peripheral nervous system in the form of autonomic ganglia and autonomic plexuses;

two-neuronality of the efferent link of the autonomic reflex arc, that is, along the path from the autonomic nucleus to the working organ there are at least two neurons.

The autonomic nervous system acts on organs in two ways: it either enhances the function of organs or weakens their functioning. Since the same nerve fiber cannot conduct impulses of opposite action, the autonomic nervous system is divided into sympathetic and parasympathetic parts.

The sympathetic part of the autonomic nervous system mainly strengthens the functions of internal organs, performs a trophic function, enhances metabolic processes in cells, enhances the secretion of glands, and increases the heart rate.

A playful teenager in the forest came across a hollow in an old willow tree, around which wasps were hovering. Not being a humanist, our hero covered the cobblestone just below the wasp's nest, and the rotten tree began to hum. The wasps, blinded by rage, rushed after the offender, and he fled, hoping to avoid punishment for his trick. At the same time, some changes occur in his body: breathing is rapid and shallow, the heart rate is increased, blood pressure is increased, the intestines, kidneys and bladder sharply reduce their function (you can’t really relieve yourself while running), your mouth is dry, your pupils are wide (fear has large eyes), pale skin, covered with sweat. So, running away from a swarm of wasps is similar to the action of the sympathetic nervous system.

The parasympathetic part of the autonomic nervous system performs protective functions - it slows down the heart rate, constricts the pupil, enhances the motility of the gastrointestinal tract, promoting faster removal of contents from it, emptying hollow organs, i.e. its action is diametrically opposite. Let's show this with the following example: a young girl, a student of the pre-revolutionary Smolny Institute for Noble Maidens, after reading a couple of chapters of a romance novel, lowered her head onto the pillow. An exalted feeling remained in her soul, and she fell asleep with a smile on her lips. Her breathing became deeper, her heart beat slower, her blood pressure dropped, and her gastrointestinal and urinary systems became more active (morning toilet). So, deep healthy sleep is similar to the parasympathetic nervous system.

There are organs that are innervated only by the sympathetic part of the autonomic nervous system - sweat glands, smooth muscles of the skin, adrenal glands.

Although the sympathetic and parasympathetic parts of the autonomic nervous system are antagonists, at the same time they act as synergists. And the state of the organ depends only on the predominance of one part. Like the rest of the nervous system, the autonomic nervous system has central and peripheral divisions.

The central part of the autonomic nervous system includes the autonomic nuclei located in the gray matter of the brain and spinal cord and the autonomic centers.

The peripheral part of the autonomic nervous system includes nerves (preganglionic and postganglionic nerve fibers), autonomic ganglia and autonomic plexuses - periorgan and intraorgan.

Autonomic nuclei (foci) are clusters of bodies of autonomic neurocytes. There are 4 autonomic nuclei, three of them are parasympathetic, and one is sympathetic.

Parasympathetic nuclei.

Mesencephalic nuclei (midcerebral) are a group of small visceral-type neurocytes located under the cerebral aqueduct. The Jakubovich nuclei or accessory nuclei are located on the sides, and the Darkshevich nucleus is located in the midline.

Bulbar nuclei - these include: a) the superior spinal nucleus, 7 pairs of cranial nerves located in the pons dorsal to the nucleus of the facial nerve; b) the lower salivary nucleus - (9 pairs) lies in the medulla oblongata between the nucleus ambiguus and the olivary nucleus and the posterior nucleus of the vagus nerve, which lies in the medulla oblongata in the triangle of the same name.

The sacral nucleus - the nuclei of the gray matter of the spinal cord (2-4 sacral segments) is a group of small oblong nerve cells of the lateral **** nucleus.

Sympathetic nuclei .

The thoracolumbar nucleus or thoracolumbar nucleus is a collection of nerve cells in the lateral horns of the gray matter of the spinal cord from the 8th cervical to the 2nd lumbar segment inclusive.

The nuclei are dominated by autonomic centers, which are not divided into sympathetic and parasympathetic, but are general, that is, depending on the signal coming from the periphery, they can excite either sympathetic or parasympathetic nuclei.

Autonomic centers are located in different parts of the brain. in the medulla oblongata - these are the vasomotor and respiratory centers, in the hindbrain - the cerebellar cortex, in the midbrain - the gray matter of the bottom of the Sylvian aqueduct, in the diencephalon - the nuclei of the hypothalamus, especially the mammillary bodies and gray tuberosity, and in the telencephalon - the basal nuclei, especially the striatum.

Peripheral part of the autonomic nervous system

Autonomic nerves– are processes of nerve cells lying in the central parts of the autonomic nervous system, in the nuclei. Upon exiting the brain and spinal cord, these processes (axons) are directed to organs either as part of other nerves or in the form of independently formed and visible nerve trunks. On the way from the center to the organ, the fibers of the autonomic nerves are necessarily interrupted in the autonomic nodes. This is the main difference between autonomic nerves and somatic nerves.

The part of the autonomic nerve that carries the nerve impulse from the center to the node is called the prenodal (preganglionic) part.

The part of the autonomic nerve that carries the impulse from the node and transmits it to the working organ is called post-nodal or postganglionic.

Autonomic nerve ganglia– their shape is varied: round, oval, star-shaped, lamellar. The size of the nodes varies widely. Large nerve nodes have a well-defined connective tissue sheath. A large number of vegetative nodes lie on both sides of the spinal column, stretching in the form of a chain, and form the spinal trunks. They are called paravertebral nodes.

Both sympathetic trunks stretch from the base of the skull to the coccyx and consist of separate sympathetic nodes connected by internodal branches. These nodes are connected to the spinal cord by myelin fibers. These fibers are preganglionic and are called white communicating branches.

Postganglionic fibers arise from the sympathetic ganglia and connect the sympathetic trunk to the spinal nerves. They are pulpless and are called gray connecting branches. Each sympathetic trunk is divided into 4 sections:

Cervical – contains 3 nodes

Thoracic – 10-12 knots

Lumbar – 3-5 knots

Sacral – 3-4 nodes.

In the coccyx area, both sympathetic trunks are connected into one node. Postganglionic fibers from the sympathetic trunk go to blood vessels, smooth muscles of the skin, glands, and striated muscles, forming trophism.

In addition to macroscopically identified nodes along the nerves, there are small groups of autonomic nerve cells - microganglia. There are vegetative nodes lying directly against the wall - periorgan or inside the wall - intramural.

Any autonomic node is a collection of neurons of the autonomic nervous system. With the help of these neurons, the node creates a certain coloring of nerve impulses and forms a wide variety of reaction states of the organs that it innervates.

In addition to nerve cells, the autonomic ganglia contain three types of nerve fibers: preganglionic, postganglionic and centripetal nerve fibers that travel from the organs through the autonomic ganglion to the central nervous system. Preganglionic fibers, having entered the nerve ganglion, divide repeatedly. They lose myelin and form numerous plexuses. Thin filaments extend from these plexuses, which are closely adjacent to the dendrites of nerve cells. They are formed in the form of rings, loops, plates and represent synapses of the central neuron of the autonomic nervous system with the neurocyte of a given node.

Some fibers pass through in transit, forming internodal connecting branches. In addition to the nodes of the sympathetic trunks, the cephalic nodes (parasympathetic) are well known: the ciliary node - in the orbit, the pterygopalatine node - in the fossa of the skull of the same name, the submandibular node - lies at the edge of the medial pterygoid muscle, the auricular node - located under the oval opening of the skull on medial side of the submandibular nerve.

Autonomic plexuses are formed by the terminal branches of the branches of the sympathetic trunk and branches of the vagus nerve. They also contain afferent fibers.

The autonomic nervous system plays no less important role in the functioning of the human body than the central one. Its various departments control the acceleration of metabolism, the renewal of energy reserves, the control of blood circulation, respiration, digestion and more. For a personal trainer, knowledge of what the human autonomic nervous system is needed for, what it consists of, and how it works is a necessary condition for his professional development.

The autonomic nervous system (also known as autonomic, visceral and ganglionic) is part of the entire nervous system of the human body and is a kind of aggregator of central and peripheral nervous formations, which are responsible for regulating the functional activity of the body, necessary for the appropriate reaction of its systems to various stimuli. It controls the functioning of internal organs, endocrine and exocrine glands, as well as blood and lymphatic vessels. Plays an important role in maintaining homeostasis and the adequate course of the body’s adaptation processes.

The work of the autonomic nervous system is in fact not controlled by humans. This suggests that a person is not able to influence the functioning of the heart or digestive tract through any effort. However, it is still possible to achieve conscious influence on many parameters and processes that are controlled by the ANS, in the process of undergoing a complex of physiological, preventive and therapeutic procedures using computer technology.

Structure of the autonomic nervous system

Both in structure and function, the autonomic nervous system is divided into sympathetic, parasympathetic and metasympathetic. The sympathetic and parasympathetic centers control the cerebral cortex and hypothalamic centers. Both the first and second sections have a central and peripheral part. The central part is formed from the cell bodies of neurons that are found in the brain and spinal cord. Such formations of nerve cells are called vegetative nuclei. Fibers that arise from the nuclei, autonomic ganglia that lie outside the central nervous system, and nerve plexuses within the walls of the internal organs form the peripheral part of the autonomic nervous system.

• The sympathetic nuclei are located in the spinal cord. The nerve fibers that branch from it end outside the spinal cord in the sympathetic ganglia, and from them the nerve fibers that go to the organs originate.
• Parasympathetic nuclei are located in the midbrain and medulla oblongata, as well as in the sacral part of the spinal cord. Nerve fibers of the nuclei of the medulla oblongata are present in the vagus nerves. The nuclei of the sacral part conduct nerve fibers to the intestines and excretory organs.

The metasympathetic nervous system consists of nerve plexuses and small ganglia within the walls of the digestive tract, as well as the bladder, heart and other organs.

Structure of the autonomic nervous system: 1- Brain; 2- Nerve fibers to the meninges; 3- Pituitary gland; 4- Cerebellum; 5- Medulla oblongata; 6, 7- Parasympathetic fibers of the ocular motor and facial nerves; 8- Star knot; 9- Border pillar; 10- Spinal nerves; 11- Eyes; 12- Salivary glands; 13- Blood vessels; 14- Thyroid gland; 15- Heart; 16- Lungs; 17- Stomach; 18- Liver; 19- Pancreas; 20- Adrenal glands; 21- Small intestine; 22- Large intestine; 23- Kidneys; 24- Bladder; 25- Genital organs.

I- Cervical region; II- Thoracic department; III- Lumbar; IV- Sacrum; V- Coccyx; VI- Vagus nerve; VII- Solar plexus; VIII- Superior mesenteric node; IX- Inferior mesenteric node; X- Parasympathetic nodes of the hypogastric plexus.

The sympathetic nervous system speeds up metabolism, increases stimulation of many tissues, and activates the body's strength for physical activity. The parasympathetic nervous system helps regenerate wasted energy reserves and also controls the functioning of the body during sleep. The autonomic nervous system controls the organs of circulation, respiration, digestion, excretion, reproduction, and among other things, metabolism and growth processes. By and large, the efferent section of the ANS controls the nervous regulation of the work of all organs and tissues with the exception of skeletal muscles, which are controlled by the somatic nervous system.

Morphology of the autonomic nervous system

The identification of the ANS is associated with the characteristic features of its structure. These features usually include: localization of the vegetative nuclei in the central nervous system; accumulation of bodies of effector neurons in the form of nodes within the autonomic plexuses; two-neuronality of the nerve pathway from the autonomic nucleus in the central nervous system to the target organ.

Structure of the spinal cord: 1- Spine; 2- Spinal cord; 3- Articular process; 4- Transverse process; 5- Spinous process; 6- Place of attachment of the rib; 7- Vertebral body; 8- Intervertebral disc; 9- Spinal nerve; 10- Central canal of the spinal cord; 11- Vertebral nerve ganglion; 12- Soft shell; 13- Arachnoid membrane; 14- Hard shell.

The fibers of the autonomic nervous system do not branch in segments, as, for example, in the somatic nervous system, but from three localized areas of the spinal cord remote from each other - the cranial sternolumbar and sacral. As for the previously mentioned sections of the autonomic nervous system, in its sympathetic part the processes of spinal neurons are short, and the ganglion ones are long. In the parasympathetic system the opposite is true. The processes of spinal neurons are longer, and those of ganglion neurons are shorter. It is worth noting here that sympathetic fibers innervate all organs without exception, while the local innervation of parasympathetic fibers is largely limited.

Divisions of the autonomic nervous system

Based on topographical characteristics, the ANS is divided into central and peripheral sections.

• Central department. It is represented by the parasympathetic nuclei of the 3rd, 7th, 9th and 10th pairs of cranial nerves running in the brain stem (craniobulbar region) and nuclei located in the gray matter of the three sacral segments (sacral region). The sympathetic nuclei are located in the lateral horns of the thoracolumbar spinal cord.
• Peripheral department. Represented by autonomic nerves, branches and nerve fibers emerging from the brain and spinal cord. This also includes the autonomic plexuses, nodes of the autonomic plexuses, the sympathetic trunk (right and left) with its nodes, internodal and connecting branches and sympathetic nerves. As well as the terminal nodes of the parasympathetic part of the autonomic nervous system.

Functions of the autonomic nervous system

The main function of the autonomic nervous system is to ensure an adequate adaptive response of the body to various stimuli. The ANS ensures control of the constancy of the internal environment, and also takes part in multiple responses that occur under the control of the brain, and these reactions can be both physiological and mental in nature. As for the sympathetic nervous system, it is activated when stress reactions occur. It is characterized by a global effect on the body, with sympathetic fibers innervating most organs. It is also known that parasympathetic stimulation of some organs leads to an inhibitory reaction, and of other organs, on the contrary, to an exciting one. In the vast majority of cases, the action of the sympathetic and parasympathetic nervous systems is opposite.

The autonomic centers of the sympathetic department are located in the thoracic and lumbar parts of the spinal cord, the centers of the parasympathetic department are located in the brain stem (eyes, glands and organs innervated by the vagus nerve), as well as in the sacral part of the spinal cord (bladder, lower colon and genitals). Preganglionic fibers of both the first and second sections of the autonomic nervous system run from the centers to the ganglia, where they end on postganglionic neurons.

Preganglionic sympathetic neurons originate in the spinal cord and end either in the paravertebral ganglion chain (in the cervical or abdominal ganglion) or in the so-called terminal ganglia. The transmission of stimulus from preganglionic neurons to postganglionic neurons is cholinergic, that is, mediated by the release of the neurotransmitter acetylcholine. Stimulation by postganglionic sympathetic fibers of all effector organs, with the exception of the sweat glands, is adrenergic, that is, mediated by the release of norepinephrine.

Now let's look at the effect of the sympathetic and parasympathetic departments on specific internal organs.

• Effect of the sympathetic department: on the pupils - has a dilating effect. On arteries – has a dilating effect. On the salivary glands - inhibits salivation. On the heart - increases the frequency and strength of its contractions. It has a relaxing effect on the bladder. On the intestines - inhibits peristalsis and enzyme production. On the bronchi and breathing - expands the lungs, improves their ventilation.
• Effect of the parasympathetic department: on the pupils - has a constricting effect. On the arteries - in most organs it has no effect, it causes dilation of the arteries of the genitals and brain, as well as a narrowing of the coronary arteries and arteries of the lungs. On the salivary glands – stimulates salivation. On the heart - reduces the strength and frequency of its contractions. On the bladder – promotes its contraction. On the intestines - enhances peristalsis and stimulates the production of digestive enzymes. On the bronchi and breathing - narrows the bronchi, reduces ventilation of the lungs.

Basic reflexes often occur within a specific organ (for example, in the stomach), but more complex (complex) reflexes pass through the controlling autonomic centers in the central nervous system, mainly in the spinal cord. These centers are controlled by the hypothalamus, whose activity is associated with the autonomic nervous system. The cerebral cortex is the most highly organized nerve center that connects the ANS with other systems.

Conclusion

The autonomic nervous system, through its subordinate structures, activates a number of simple and complex reflexes. Some fibers (afferents) carry stimuli from the skin and pain receptors in organs such as the lungs, gastrointestinal tract, gallbladder, vascular system and genitals. Other fibers (efferent) conduct a reflex response to afferent signals, implementing smooth muscle contractions in organs such as the eyes, lungs, digestive tract, gall bladder, heart and glands. Knowledge about the autonomic nervous system, as one of the elements of the integral nervous system of the human body, is an integral part of the theoretical minimum that a personal trainer should have.

After studying the material in the chapter, the student should:

know

Principles of the structure and functioning of the autonomic nervous system;

be able to

• demonstrate the sympathetic trunk and cranial vegetative nodes on preparations and tables;
• schematically depict the structure of the reflex arc of the autonomic nervous system;

own

Skills in predicting functional disorders due to damage to the structures of the autonomic nervous system.

The autonomic (autonomic) nervous system provides innervation to internal organs, glands, blood vessels, smooth muscles and performs an adaptive-trophic function. Like the somatic nervous system, it operates through reflexes. For example, when the stomach receptors are irritated, impulses are sent to this organ through the vagus nerve, enhancing the secretion of its glands and activating motility. As a rule, autonomic reflexes are not controlled by consciousness, i.e. occur automatically after certain irritations. A person cannot voluntarily increase or decrease the heart rate, increase or suppress the secretion of glands.

As in the simple somatic reflex arc, the autonomic reflex arc contains three neurons. The body of the first of them (sensitive or receptor) is located in the spinal ganglion or in the corresponding sensory ganglion of the cranial nerve. The second neuron is an association cell, located in the vegetative nuclei of the brain or spinal cord. The third neuron is the effector neuron, located outside the central nervous system in the paravertebral and prevertebral - sympathetic or intramural and cranial - parasympathetic nodes (ganglia). Thus, the arcs of somatic and autonomic reflexes differ from each other by the location of the effector neuron. In the first case, it lies within the central nervous system (motor nuclei of the anterior horns of the spinal cord or motor nuclei of the cranial nerves), and in the second - on the periphery (in the vegetative ganglia).

The autonomic nervous system is also characterized by a segmental type of innervation. The centers of autonomic reflexes have a specific localization in the central nervous system, and impulses to the organs pass through the corresponding nerves. Complex autonomic reflexes are performed with the participation of the suprasegmental apparatus. Suprasegmental centers are localized in the hypothalamus, limbic system, reticular formation, cerebellum and in the cerebral cortex.

Functionally, the sympathetic and parasympathetic divisions of the autonomic nervous system are distinguished.

Sympathetic nervous system

The sympathetic part of the autonomic nervous system is divided into central and peripheral sections. The central one is represented by nuclei located in the lateral horns of the spinal cord along the length from the 8th cervical to the 3rd lumbar segment. All fibers going to the sympathetic ganglia begin from the neurons of these nuclei. They exit the spinal cord as part of the anterior roots of the spinal nerves.

The peripheral division of the sympathetic nervous system includes nodes and fibers located outside the central nervous system.

Sympathetic trunk– a paired chain of paravertebral nodes, running parallel to the spinal column (Fig. 9.1). It extends from the base of the skull to the coccyx, where the right and left trunks come together and end in a single coccygeal node. White connecting branches from the spinal nerves containing preganglionic fibers approach the nodes of the sympathetic trunk. Their length, as a rule, does not exceed 1–1.5 cm. These branches are present only in those nodes that correspond to the segments of the spinal cord containing sympathetic nuclei (8th cervical - 3rd lumbar). The fibers of the white connecting branches switch to the neurons of the corresponding ganglia or pass through them in transit to the superior and underlying nodes. In this regard, the number of nodes of the sympathetic trunk (25–26) exceeds the number of white connecting branches. Some fibers do not end in the sympathetic trunk, but, bypassing it, go to the abdominal aortic plexus. They form the greater and lesser splanchnic nerves. Between adjacent nodes of the sympathetic trunk there are internodal branches, ensuring the exchange of information between its structures. Unmyelinated postganglionic fibers emerge from the ganglia - gray connecting branches, which return to the spinal nerves, and the bulk of the fibers are sent to the organs along the large arteries.

The greater and lesser splanchnic nerves pass in transit (without switching) through the 6–9th and 10–12th thoracic nodes, respectively. They participate in the formation of the abdominal aortic plexus.

According to the segments of the spinal cord, the cervical (3 nodes), thoracic (10–12), lumbar (5) and sacral (5) sections of the sympathetic trunk are distinguished. The single coccygeal ganglion is usually rudimentary.

Upper cervical knot - the biggest. Its branches run mainly along the external and internal carotid arteries, forming plexuses around them. They provide sympathetic innervation to the organs of the head and neck.

Middle cervical node unstable, lies at the level of the VI cervical vertebra. Gives branches to the heart, thyroid and parathyroid glands, to the vessels of the neck.

Lower cervical knot located at the level of the neck of the first rib, often merges with the first thoracic and has a star-shaped shape. In this case it is called cervicothoracic (star-shaped) knot. Gives off branches for innervation of the organs of the anterior mediastinum (including the heart), thyroid and parathyroid glands.

Branches that participate in the formation of the thoracic aortic plexus extend from the thoracic sympathetic trunk. They provide innervation to the organs of the thoracic cavity. In addition, it starts from big And small visceral (celiac) nerves, which consist of pretanglionic fibers and transit through the 6th–12th nodes. They pass through the diaphragm into the abdominal cavity and end on the neurons of the celiac plexus.

Rice. 9.1.

1 – ciliary node; 2 – pterygopalatine node; 3 – sublingual node; 4 – ear node; 5 – nodes of the celiac plexus; 6 – pelvic splanchnic nerves

The lumbar nodes of the sympathetic trunk are connected to each other not only by longitudinal, but also by transverse internodal branches that connect the ganglia of the right and left sides (see Fig. 8.4). Fibers extend from the lumbar ganglia into the abdominal aortic plexus. Along the vessels, they provide sympathetic innervation to the walls of the abdominal cavity and lower extremities.

The pelvic section of the sympathetic trunk is represented by five sacral and rudimentary coccygeal nodes. The sacral nodes are also interconnected by transverse branches. The nerves extending from them provide sympathetic innervation to the pelvic organs.

Abdominal aortic plexus located in the abdominal cavity on the anterior and lateral surfaces of the abdominal aorta. This is the largest plexus of the autonomic nervous system. It is formed by several large prevertebral sympathetic ganglia, branches of the greater and lesser splanchnic nerves approaching them, and numerous nerve trunks and branches extending from the nodes. The main nodes of the abdominal aortic plexus are paired pregnant And aortorenal and unpaired superior mesenteric nodes. As a rule, postganglionic sympathetic fibers depart from them. Numerous branches extend from the celiac and superior mesenteric nodes in different directions, like the rays of the sun. This explains the old name of the plexus - "solar plexus".

The branches of the plexus continue on the artery, forming secondary autonomic plexuses of the abdominal cavity (choroid autonomic plexuses) around the vessels. These include unpaired: celiac (entwines the celiac trunk), splenic (splenic artery), hepatic (proprietary hepatic artery) top And inferior mesenteric (along the course of the arteries of the same name) plexus. Paired are gastric, adrenal, renal, testicular (ovarian )plexus, located around the vessels of these organs. Along the vessels, postganglionic sympathetic fibers reach the internal organs and innervate them.

Superior and inferior hypogastric plexuses. The superior hypogastric plexus is formed from branches of the abdominal aortic plexus. In shape, it is a triangular plate located on the anterior surface of the V lumbar vertebra, under the bifurcation of the aorta. Downwards the plexus gives off fibers that participate in the formation of the inferior hypogastric plexus. The latter is located above the levator ani muscle, at the site of division of the common iliac artery. Branches extend from these plexuses, providing sympathetic innervation to the pelvic organs.

Thus, the autonomic nodes of the sympathetic nervous system (para- and prevertebral) are located near the spinal cord at a certain distance from the innervated organ. Accordingly, the preganglionic sympathetic fiber has a short length, and the postganglionic fiber has a longer length. At a neurotissue synapse, the transmission of a nerve impulse from a nerve to a tissue occurs due to the release of the mediator norepinephrine.

Parasympathetic nervous system

The parasympathetic part of the autonomic nervous system is divided into central and peripheral sections. The central section is represented by the parasympathetic nuclei of the III, VII, IX and X cranial nerves and the parasympathetic sacral nuclei of the spinal cord. The peripheral section includes parasympathetic fibers and nodes. The latter, unlike the sympathetic nervous system, are located either in the wall of the organs that they innervate or next to them. Accordingly, preganglionic (myelin) fibers are longer than postganglionic fibers. Impulse transmission at the neurotissue synapse in the parasympathetic nervous system is ensured primarily by the mediator acetylcholine.

Parasympathetic fibers ( additional ) kernels III pair of cranial nerves(oculomotor nerve) in the orbit end on cells ciliary node. Postganglionic parasympathetic fibers begin from it, which penetrate the eyeball and innervate the muscle that constricts the pupil and the ciliary muscle (provides accommodation). Sympathetic fibers arising from the superior cervical ganglion of the sympathetic trunk innervate the muscle that dilates the pupil.

The pons contains the parasympathetic nuclei ( upper salivary And tearful ) VII pairs of cranial nerves(facial nerve). Their axons branch from the facial nerve and comprise greater petrosal nerve reach pterygopalatine node, located in the pit of the same name (see Fig. 7.1). Postganglionic fibers begin from it, carrying out parasympathetic innervation of the lacrimal gland, glands of the mucous membranes of the nasal cavity and palate. Some of the fibers that are not included in the greater petrosal nerve are directed to drum string. The latter carries preganglionic fibers to submandibular And sublingual nodes. The axons of the neurons of these nodes innervate the salivary glands of the same name.

Inferior salivary nucleus belongs to the glossopharyngeal nerve ( IX pair). Its preganglionic fibers first pass through drum, and then - lesser petrosal nerve To ear node. Branches extend from it, providing parasympathetic innervation of the parotid salivary gland.

From dorsal nucleus of the vagus nerve (X pair), parasympathetic fibers as part of its branches pass to numerous intramural nodes located in the wall of the internal organs of the neck, [ore and abdominal cavities. Postganglionic fibers depart from these nodes, providing parasympathetic innervation to the organs of the neck, chest cavity, and most abdominal organs.

Sacral division of the parasympathetic nervous system represented by sacral parasympathetic nuclei located at the level of II–IV sacral segments. Fibers originate from them pelvic splanchnic nerves, which carry impulses to the intramural nodes of the pelvic organs. Postganglionic fibers extending from them provide parasympathetic innervation of the internal genital organs, bladder and rectum.

The autonomic (autonomic) nervous system (systema nervosum autonomicum) is a part of the nervous system that controls the functions of internal organs, glands, blood vessels, and exercises an adaptive-trophic influence on all human organs. The autonomic nervous system maintains the constancy of the internal environment of the body (homeostasis). The function of the autonomic nervous system is not controlled by human consciousness, but it is subordinate to the spinal cord, cerebellum, hypothalamus, basal ganglia of the telencephalon, limbic system, reticular formation and cerebral cortex.

The distinction of the autonomic (autonomic) nervous system is due to certain features of its structure. These features include the following:

1. focal location of vegetative nuclei in the central nervous system;
2. accumulation of bodies of effector neurons in the form of nodes (ganglia) as part of the peripheral autonomic plexuses;
3. two-neuronality of the nerve pathway from the nuclei in the central nervous system to the innervated organ;
4. preservation of features reflecting the slower evolution of the autonomic nervous system (compared to the animal one): smaller caliber of nerve fibers, lower speed of excitation, and the absence of a myelin sheath in many nerve conductors.

The autonomic (autonomic) nervous system is divided into central and peripheral sections.

TO central department relate:

1. parasympathetic nuclei of III, VII, IX and X pairs of cranial nerves lying in the brain stem (midbrain, pons, medulla oblongata);
2. parasympathetic sacral nuclei located in the gray matter of the three sacral segments of the spinal cord (SII-SIV);
3. vegetative (sympathetic) nucleus located in the lateral intermediate column [lateral intermediate (gray) substance] of the VIII cervical, all thoracic and two upper lumbar segments of the spinal cord (CVIII-ThI-LII).

TO peripheral department The autonomic (autonomic) nervous system includes:

1. autonomic (autonomic) nerves, branches and nerve fibers emerging from the brain and spinal cord;
2. vegetative (autonomous) visceral plexuses;
3. nodes of the vegetative (autonomous, visceral) plexuses;
4. sympathetic trunk (right and left) with its nodes, internodal and connecting branches and sympathetic nerves;
5. nodes of the parasympathetic part of the autonomic nervous system;
6. vegetative fibers (parasympathetic and sympathetic), going to the periphery (to organs, tissues) from the vegetative nodes that are part of the plexuses and located in the thickness of the internal organs;
7. nerve endings involved in autonomic reactions.

Neurons of the nuclei of the central part of the autonomic nervous system are the first efferent neurons on the paths from the central nervous system (spinal cord and brain) to the innervated organ. The fibers formed by the processes of these neurons are called prenodal (preganglionic) nerve fibers, since they go to the nodes of the peripheral part of the autonomic nervous system and end with synapses on the cells of these nodes.

Autonomic nodes are part of the sympathetic trunks, large autonomic plexuses of the abdominal cavity and pelvis, and are also located in the thickness or near the organs of the digestive, respiratory systems and genitourinary apparatus, which are innervated by the autonomic nervous system.

The size of the vegetative nodes is determined by the number of cells located in them, which ranges from 3000-5000 to many thousands. Each node is enclosed in a connective tissue capsule, the fibers of which, penetrating deep into the node, divide it into lobules (sectors). Between the capsule and the body of the neuron are located satellite cells - a type of glial cells.

Glial cells (Schwann cells) include neurolemmocytes, which form the sheaths of peripheral nerves. Autonomic ganglion neurons are divided into two main types: Dogel cells type I and type II. Type I Dogel cells are efferent; preganglionic processes end on them. These cells are characterized by a long, thin, non-branching axon and many (from 5 to several dozen) dendrites branching near the body of this neuron. These cells have several slightly branched processes, among which there is an axon. They are larger than type I Dogel neurons. Their axons enter into synaptic communication with Dogel type I efferent neurons.

Preganglionic fibers have a myelin sheath, which gives them a whitish color. They leave the brain as part of the roots of the corresponding cranial and spinal nerves. The nodes of the peripheral part of the autonomic nervous system contain the bodies of second efferent (effector) neurons lying on the paths to the innervated organs. The processes of these second neurons, carrying the nerve impulse from the autonomic ganglia to the working organs (smooth muscles, glands, vessels, tissues), are post-nodal (postganglionic) nerve fibers. They do not have a myelin sheath and are therefore gray in color.

The speed of impulses along sympathetic preganglionic fibers is 1.5-4 m/s, and parasympathetic - 10-20 m/s. The speed of impulse conduction along postganglionic (unmyelinated) fibers does not exceed 1 m/s.

The bodies of afferent nerve fibers of the autonomic nervous system are located in the spinal (intervertebral) nodes, as well as in the sensory nodes of the cranial nerves; in the own sensory nodes of the autonomic nervous system (Dogel cells type II).

The structure of the reflex autonomic arc differs from the structure of the reflex arc of the somatic part of the nervous system. In the reflex arc of the autonomic nervous system, the efferent link consists not of one neuron, but of two. In general, a simple autonomic reflex arc is represented by three neurons. The first link of the reflex arc is a sensory neuron, the body of which is located in the spinal ganglia or ganglia of the cranial nerves. The peripheral process of such a neuron, which has a sensitive ending - a receptor, originates in organs and tissues. The central process, as part of the dorsal roots of the spinal nerves or sensory roots of the cranial nerves, is directed to the corresponding autonomic nuclei of the spinal cord or brain. The efferent (outflow) path of the autonomic reflex arc is represented by two neurons. The body of the first of these neurons, the second in a simple autonomic reflex arc, is located in the autonomic nuclei of the central nervous system. This neuron can be called an intercalary one, since it is located between the sensitive (afferent, afferent) link of the reflex arc and the third (efferent, efferent) neuron of the efferent path. The effector neuron is the third neuron of the autonomic reflex arc. The bodies of effector neurons lie in the peripheral nodes of the autonomic nervous system (sympathetic trunk, autonomic nodes of the cranial nerves, nodes of extra- and intraorgan autonomic plexuses). The processes of these neurons are directed to organs and tissues as part of organ autonomic or mixed nerves. Postganglionic nerve fibers end in smooth muscles, glands, in the walls of blood vessels and in other tissues with the corresponding terminal nerve apparatus.

Based on the topography of the autonomic nuclei and nodes, differences in the length of the first and second neurons of the efferent pathway, as well as the characteristics of the functions, the autonomic nervous system is divided into two parts: sympathetic and parasympathetic.

Physiology of the autonomic nervous system

The autonomic nervous system controls blood pressure (BP), heart rate (HR), temperature and body weight, digestion, metabolism, water and electrolyte balance, sweating, urination, defecation, sexual reactions and other processes. Many organs are controlled primarily by either the sympathetic or parasympathetic system, although they can receive input from both parts of the autonomic nervous system. More often, the effect of the sympathetic and parasympathetic systems on the same organ is exactly the opposite, for example, sympathetic stimulation increases the heart rate, and parasympathetic stimulation decreases it.

The sympathetic nervous system promotes intense body activity (catabolic processes) and hormonally provides the “fight or flight” phase of the stress response. Thus, sympathetic efferent signals increase heart rate and myocardial contractility, cause bronchodilation, activate glycogenolysis in the liver and glucose release, increase basal metabolic rate and muscle strength; and also stimulate sweating in the palms. Life-supporting functions that are less important in a stressful environment (digestion, renal filtration) are reduced under the influence of the sympathetic autonomic nervous system. But the process of ejaculation is completely under the control of the sympathetic department of the autonomic nervous system.

The parasympathetic nervous system helps restore resources expended by the body, i.e. provides anabolic processes. The parasympathetic autonomic nervous system stimulates the secretion of the digestive glands and gastrointestinal motility (including evacuation), reduces heart rate and blood pressure, and promotes erection.

The functions of the autonomic nervous system are provided by two main neurotransmitters - acetylcholine and norepinephrine. Depending on the chemical nature of the mediator, nerve fibers secreting acetylcholine are called cholinergic; these are all preganglionic and all postganglionic parasympathetic fibers. Fibers that secrete norepinephrine are called adrenergic; these are the majority of postganglionic sympathetic fibers, with the exception of those innervating blood vessels, sweat glands and muscles of the arectores pilorum, which are cholinergic. Palmar and plantar sweat glands partially respond to adrenergic stimulation. Subtypes of adrenergic and cholinergic receptors are distinguished depending on their location.

Autonomic Nervous System Assessment

Autonomic dysfunction may be suspected if symptoms such as orthostatic hypotension, heat intolerance, and loss of bowel and bladder control are present. Erectile dysfunction is one of the early symptoms of dysfunction of the autonomic nervous system. Xerophthalmia and xerostomia are not specific symptoms of dysfunction of the autonomic nervous system.

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Physical examination

Sustained decrease in systolic blood pressure by more than 20 mm Hg. Art. or diastolic by more than 10 mm Hg. Art. after assuming a vertical position (in the absence of dehydration) suggests the presence of autonomic dysfunction. You should pay attention to changes in heart rate (HR) during breathing and when changing body position. The absence of respiratory arrhythmia and insufficient increase in heart rate after assuming a vertical position indicate autonomic dysfunction.

Miosis and moderate ptosis (Horner's syndrome) indicate damage to the sympathetic part of the autonomic nervous system; a dilated pupil that does not respond to light (Eydie's pupil) indicates damage to the parasympathetic autonomic nervous system.

Abnormal genitourinary and rectal reflexes may also be symptoms of autonomic nervous system deficiency. The study includes assessment of the cremasteric reflex (normally, streak irritation of the skin of the thigh leads to the raising of the testicles), the anal reflex (normally, streak irritation of the perianal skin leads to contraction of the anal sphincter) and bulbo-cavernous reflex (normally, compression of the glans penis or clitoris leads to contraction of the anal sphincter ).

Laboratory research

If there are symptoms of autonomic dysfunction, in order to determine the severity of the pathological process and an objective quantitative assessment of the autonomic regulation of the cardiovascular system, a cardiovagal test, tests for the sensitivity of peripheral α-adrenergic receptors, as well as a quantitative assessment of sweating are performed.

Quantitative sudomotor axon reflex test tests the function of postganglionic neurons. Local sweating is stimulated by acetylcholine iontophoresis, electrodes are placed on the lower leg and wrist, and the severity of sweating is recorded by a special suedometer, which transmits information in analog form to a computer. The test result may be decreased sweating, no sweating, or continued sweating after stimulation has stopped. Using a thermoregulatory test, the state of preganglionic and postganglionic pathways is assessed. Dye tests are used much less frequently to assess sweating function. After applying the paint to the skin, the patient is placed in a closed room, which is heated until maximum sweating is achieved; sweating causes a change in paint color, which reveals areas of anhidrosis and hypohidrosis and allows for their quantitative analysis. The absence of sweating indicates damage to the efferent part of the reflex arc.

Cardiovagal tests evaluate the heart rate response (ECG recording and analysis) to deep breathing and the Valsalva maneuver. If the autonomic nervous system is intact, then the maximum increase in heart rate is observed after the 15th heart beat and a decrease after the 30th. The ratio between the RR intervals at the 15th-30th beat (i.e., the longest interval to the shortest) - the ratio is 30:15 - is normally 1.4 (Valsalva ratio).

Tests for the sensitivity of peripheral adrenergic receptors include studying heart rate and blood pressure in the tilt test (passive orthotest) and the Valsalva maneuver. When performing a passive orthotest, a redistribution of blood volume occurs to the underlying parts of the body, which causes reflex hemodynamic reactions. The Valsalva maneuver evaluates changes in blood pressure and heart rate as a result of increased intrathoracic pressure (and decreased venous inflow), which causes characteristic changes in blood pressure and reflex vasoconstriction. Normally, changes in hemodynamic parameters occur within 1.5-2 minutes and have 4 phases, during which blood pressure increases (1st and 4th phases) or decreases after a rapid recovery (2nd and 3rd phases). Heart rate increases in the first 10 s. When the sympathetic department is damaged, a blockade of the response occurs in the 2nd phase.