The structure of the sympathetic nervous system. Autonomic nervous system: structure and functions

The sympathetic system mobilizes the body’s forces in emergency situations, increases the waste of energy resources; parasympathetic - promotes restoration and accumulation of energy resources.

The activity of the sympathetic nervous system and the secretion of adrenaline by the adrenal medulla are related to each other, but do not always change to the same extent. Thus, with particularly strong stimulation of the sympathoadrenal system (for example, during general cooling or intense physical activity), the secretion of adrenaline increases, enhancing the action of the sympathetic nervous system. In other situations, sympathetic activity and adrenaline secretion may be independent. In particular, the orthostatic response primarily involves the sympathetic nervous system, while the response to hypoglycemia primarily involves the adrenal medulla.

Most preganglionic sympathetic neurons have thin myelinated axons - B fibers. However, some axons are unmyelinated C-fibers. The conduction velocity along these axons ranges from 1 to 20 m/s. They leave the spinal cord as part of the ventral roots and white communicating rami and end in paired paravertebral ganglia or unpaired prevertebral ganglia. Through nerve branches, the paraventebral ganglia are connected into sympathetic trunks running on both sides of the spine from the base of the skull to the sacrum. Thinner unmyelinated postganglionic axons arise from the sympathetic trunks, which either go to peripheral organs as part of the gray connecting branches, or form special nerves going to the organs of the head, chest, abdominal and pelvic cavities. Postganglionic fibers from the prevertebral ganglia (celiac, superior and inferior mesenteric) go through the plexuses or as part of special nerves to the abdominal organs and pelvic organs.

Preganglionic axons leave the spinal cord as part of the anterior root and enter the paravertebral ganglion at the level of the same segment through the white communicating branches. White connecting branches are present only at levels Th1-L2. Preganglionic axons end at synapses in this ganglion or, after passing through it, enter the sympathetic trunk (sympathetic chain) of the paravertebral ganglia or the splanchnic nerve (Fig. 41.2).

As part of the sympathetic chain, preganglionic axons are directed rostrally or caudally to the nearest or distant paravertebral ganglion and form synapses there. Having left it, the axons go to the spinal nerve, usually through the gray connecting branch, which each of the 31 pairs has spinal nerves. As part of the peripheral nerves, postganglionic axons enter the effectors of the skin (piloerector muscles, blood vessels, sweat glands), muscles, and joints. Typically, postganglionic axons are unmyelinated (C fibers), although there are exceptions. The differences between the white and gray connecting branches depend on their relative content of myelinated and unmyelinated axons.

As part of the splanchnic nerve, preganglionic axons often go to the prevertebral ganglion, where they form synapses, or they can pass through the ganglion, ending in a more distal ganglion. Some of them, running as part of the splanchnic nerve, end directly on the cells of the adrenal medulla.

The sympathetic chain stretches from the cervical to the coccygeal level of the spinal cord. It acts as a distribution system, allowing preganglionic neurons, which are located only in the thoracic and upper lumbar segments, to activate postganglionic neurons, which supply all segments of the body. However, there are fewer paravertebral ganglia than spinal segments, since some ganglia fuse during ontogeny. For example, the superior cervical sympathetic ganglion is composed of fused C1-C4 ganglia, the middle cervical sympathetic ganglion is composed of C5-C6, and the inferior cervical sympathetic ganglion is composed of C7-C8. The stellate ganglion is formed by the fusion of the inferior cervical sympathetic ganglion with the Th1 ganglion. The superior cervical ganglion provides postganglionic innervation to the head and neck, and the middle cervical and stellate - the heart, lungs and bronchi.

Typically, the axons of preganglionic sympathetic neurons distribute to the ipsilateral ganglia and therefore regulate autonomic functions on the same side of the body. An important exception is the bilateral sympathetic innervation of the intestines and pelvic organs. Like the motor nerves of skeletal muscles, the axons of preganglionic sympathetic neurons belonging to specific organs innervate several segments. Thus, preganglionic sympathetic neurons that provide sympathetic functions to the head and neck areas are located in the C8-Th5 segments, and those belonging to the adrenal glands are in Th4-Th12.

VEGETATIVE (AUTONOMOUS) NERVOUS SYSTEM

Vegetative nervous system, like the entire nervous system, consists of neurons and their processes - nerve fibers. The autonomic nervous system is characterized by a two-neuron structure. The first neurons of the autonomic nervous system are located in the brain (middle and medulla oblongata) and spinal cord, where they form clusters - autonomic nuclei. The axons of the first neurons (nerve fibers) leave the central nervous system and end in special nodes (ganglia) located near spinal column, near internal organs or in their walls, on second neurons. The axons of the second neurons go to the innervated organ.

Nerve fibers of the autonomic nervous system emerge from the brain or spinal cord as part of some cranial and spinal nerves and approach the cells of the autonomic ganglia. They are called preganglionic. Postganglionic nerve fibers, in turn, depart from the nodes, which innervate the internal organs. The fibers of the autonomic nervous system form autonomic nerve plexuses near organs and in their walls. These plexuses contain neurons. The autonomic nuclei, located in the brain and spinal cord, constitute the central part of the autonomic nervous system, and the nerve ganglia and fibers constitute its peripheral part.

The autonomic nervous system is divided into two divisions: sympathetic and parasympathetic. Each of them is characterized by its own characteristics. The higher nerve centers of the autonomic nervous system are located in the hypothalamus: in the anterior nuclei - the centers of the parasympathetic, in the posterior nuclei - the centers of the sympathetic departments.

The sympathetic division of the autonomic nervous system includes the lateral horns of the spinal cord (sympathetic neurons of these horns, constituting the central part sympathetic division autonomic nervous system), borderline sympathetic trunk, sympathetic nerve plexuses and sympathetic nerve fibers.

The sympathetic division of the autonomic nervous system has the following structural features:

1) is formed by nerve fibers extending in symmetrical pairs on both sides of the spinal cord from neurons of the thoracic and lumbar segments (from the first thoracic to the second - fourth lumbar). The processes of the cells of the lateral horns emerge from the spinal cord as part of the corresponding spinal nerves, separate from them and approach the border sympathetic trunk;

2) ganglia are located far from the innervated organs in the form of a chain on both sides of the spinal cord (borderline sympathetic trunk) or in the form of a cluster far from the spinal cord (solar plexus, etc.);

3) preganglionic fibers are short;

4) postganglionic fibers are long.

Functions of sympathetic innervation.

Sympathetic innervation is universal; sympathetic nerves innervate the tissues of all organs, skeletal muscles and blood vessels. The transmission of impulses from the postganglionic fiber to the organ is carried out using a mediator norepinephrine

Sympathetic nerve fibers stimulate the heart (increase and increase contractions), sweat glands, muscle metabolism, constrict blood vessels, inhibit activity digestive system(weaken juice secretion and inhibit motor skills), dilate the pupils, relax the bladder wall, etc.

Fibers cervical region The sympathetic trunk innervates the blood vessels and organs of the neck and head, to which the branches of the carotid arteries approach: the pharynx, salivary glands, lacrimal glands, muscle that dilates the pupil, etc. The fibers of the thoracic region, from which the greater and lesser splanchnic nerves depart, innervate the thoracic aorta, esophagus, bronchi and lungs. Fibers of the lumbar and pelvic regions and solar plexus innervate all organs of the abdominal cavity, fibers of the hypogastric plexus innervate the pelvic organs.

Autonomic nervous system in functioning human body plays no less important role 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. Knowledge about what the human autonomic nervous system is for, what it consists of, and how it works is important for a personal trainer. a necessary condition 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 work 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 going through a complex of physiological, preventive and medical 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 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 meninges; 3- Pituitary gland; 4- Cerebellum; 5- Medulla; 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 division of the ANS controls nervous regulation 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 release of the ANS is associated with characteristic features its structures. 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; 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. Represented by parasympathetic nuclei 3, 7, 9 and 10 pairs cranial nerves, lying 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 provides control over constancy internal environment, and also takes part in multiple responses occurring under the control of the brain, and these reactions can be both physiological and mental character. 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 production 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 (afferent) 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.

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In this article we will look at what the sympathetic and parasympathetic nervous systems are, how they work, and what are their differences. We have previously covered the topic as well. The autonomic nervous system, as is known, consists of nerve cells and processes, thanks to which the regulation and control of internal organs occurs. The autonomic system is divided into peripheral and central. If the central one is responsible for the work of internal organs, without any division into opposite parts, then the peripheral one is divided into sympathetic and parasympathetic.

The structures of these departments are present in every internal organ of a person and, despite their opposing functions, they work simultaneously. However, at different times, one or another department turns out to be more important. Thanks to them, we can adapt to different climatic conditions and other changes in external environment. The autonomic system plays a very important role; it regulates mental and physical activity, and also maintains homeostasis (constancy of the internal environment). If you are resting, vegetative system The parasympathetic is activated and the number of heart contractions decreases. If you start running and experience heavy physical activity, the sympathetic department turns on, thereby speeding up the heart and blood circulation in the body.

And this is only a small slice of the activity that the visceral nervous system carries out. It also regulates hair growth, contraction and dilation of pupils, the functioning of one or another organ, is responsible for the psychological balance of the individual, and much more. All this happens without our conscious participation, which is why at first glance it seems difficult to treat.

Sympathetic nervous system

Among people who are unfamiliar with the work of the nervous system, there is an opinion that it is one and indivisible. However, in reality everything is different. Thus, the sympathetic department, which in turn belongs to the peripheral, and the peripheral belongs to the autonomic part of the nervous system, supplies the body with the necessary nutrients. Thanks to its work, oxidative processes proceed quite quickly, if necessary, the work of the heart accelerates, the body receives the proper level of oxygen, and breathing improves.

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Interestingly, the sympathetic division is also divided into peripheral and central. If the central part is an integral part of the work of the spinal cord, then the peripheral part of the sympathetic has many branches and nerve nodes that connect. The spinal center is located in the lateral horns of the lumbar and thoracic segment. The fibers, in turn, extend from the spinal cord (1st and 2nd thoracic vertebrae) and 2,3,4 lumbar vertebrae. This is very short description where the divisions of the sympathetic system are located. Most often, the SNS is activated when a person finds himself in a stressful situation.

Peripheral department

It is not so difficult to imagine the peripheral part. It consists of two identical trunks, which are located on both sides along the entire spine. They start from the base of the skull and end at the tailbone, where they converge into a single unit. Thanks to the internodal branches, the two trunks are connected. As a result, the peripheral section of the sympathetic system passes through the cervical, thoracic and lumbar regions, which we will consider in more detail.

• Cervical region. As you know, it starts from the base of the skull and ends at the transition to the thoracic (cervical 1st ribs). There are three sympathetic nodes here, which are divided into lower, middle and upper. All of them pass behind the human carotid artery. The upper node is located at the level of the second and third cervical vertebrae, has a length of 20 mm, a width of 4 - 6 millimeters. The middle one is much more difficult to find, as it is located at intersections carotid artery and thyroid gland. The lower node has the largest size, sometimes even merging with the second thoracic node.
• Thoracic department. It consists of up to 12 nodes and has many connecting branches. They reach out to the aorta, intercostal nerves, heart, lungs, thoracic duct, esophagus and other organs. Thanks to the thoracic region, a person can sometimes feel the organs.
• The lumbar region most often consists of three nodes, and in some cases has 4. It also has many connecting branches. The pelvic region connects the two trunks and other branches together.

Parasympathetic Division

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This part of the nervous system begins to work when a person tries to relax or is at rest. Thanks to the parasympathetic system, blood pressure decreases, blood vessels relax, pupils constrict, heartbeat slows down, sphincters relax. The center of this department is located in the spinal cord and brain. Thanks to efferent fibers, the hair muscles relax, sweat secretion is delayed, and blood vessels dilate. It is worth noting that the structure of the parasympathetic includes the intramural nervous system, which has several plexuses and is located in the digestive tract.

The parasympathetic department helps to recover from heavy loads and performs the following processes:

• Reduces arterial pressure;
• Restores breathing;
• Dilates blood vessels in the brain and genital organs;
• Constricts the pupils;
• Restores optimal glucose levels;
• Activates the digestive secretion glands;
• Tones the smooth muscles of internal organs;
• Thanks to this department, cleansing occurs: vomiting, coughing, sneezing and other processes.

To make the body feel comfortable and adapt to different climatic conditions, V different period the sympathetic and parasympathetic divisions of the autonomic nervous system are activated. In principle, they work constantly, however, as mentioned above, one of the departments always prevails over the other. Once in the heat, the body tries to cool itself and actively secretes sweat; when it urgently needs to warm up, sweating is accordingly blocked. If the autonomic system works correctly, a person does not experience certain difficulties and does not even know about their existence, except for professional necessity or curiosity.

Since the theme of the site is dedicated vegetative-vascular dystonia, you should know that due to psychological disorders, autonomous system experiencing glitches. For example, when a person has psychological trauma and he experiences panic attack in a closed room, his sympathetic or parasympathetic department is activated. This is a normal reaction of the body to an external threat. As a result, a person feels nausea, dizziness and other symptoms, depending on. The main thing that the patient should understand is that this is only psychological disorder, and not physiological deviations, which are only a consequence. This is why medication treatment is not an effective remedy; they only help relieve symptoms. For a full recovery, you need the help of a psychotherapist.

If at a certain point in time the sympathetic department is activated, blood pressure increases, the pupils dilate, constipation begins, and anxiety increases. When the parasympathetic action occurs, the pupils constrict, fainting may occur, blood pressure decreases, excess weight accumulates, and indecision appears. The most difficult thing is for a patient suffering from a disorder of the autonomic nervous system when he has it, since at this moment disorders of the parasympathetic and sympathetic parts of the nervous system are simultaneously observed.

Bottom line, if you suffer from an autonomic nervous system disorder, the first thing you should do is undergo numerous tests to rule out physiological pathologies. If nothing is revealed, it is safe to say that you need the help of a psychologist who short time will relieve the disease.

Historically sympathetic part arises as a segmental section, therefore in humans it partially retains the segmental nature of the structure. The sympathetic department is trophic in its main functions. It enhances oxidative processes, consumption nutrients, increased breathing, increased heart activity, increased oxygen supply to the muscles.

Central division of the sympathetic part

The central section of the sympathetic part is located in the lateral horns of the spinal cord at the level of C8, Th1-L3, in the substantia intermedia lateralis. Fibers depart from it, innervating the involuntary muscles of the internal organs, sensory organs (eyes), and glands. In addition, vasomotor and sweating centers are located here. They believe (and this is confirmed clinical experience), What various departments spinal cord affect trophism, thermoregulation and metabolism.

Peripheral division sympathetic part

The peripheral section of the sympathetic part is formed primarily by two symmetrical trunks, trunci sympathici dexter, et sinister, located on the sides of the spine along its entire length from the base of the skull to the coccyx, where both trunks with their caudal ends converge in one common node. Each of these two sympathetic trunks is composed of a number of first-order nerve ganglia, interconnected by longitudinal internodal branches, rami interganglionares, consisting of nerve fibers. In addition to the nodes of the sympathetic trunks (ganglia trunci sympathici), the sympathetic system includes the above-mentioned ganglia intermedia.

Sympathetic trunk, starting from the upper cervical node, also contains elements of the parasympathetic part of the autonomic and even animal nervous systems. The processes of cells embedded in the lateral horns of the thoracolumbar part of the spinal cord exit the spinal cord through the anterior roots and, having separated from them, go as part of the rami communicantes albi to the sympathetic trunk. Here they either synapse with the cells of the nodes of the sympathetic trunk, or, passing through its nodes without interruption, they reach one of the intermediate nodes. This is the so-called preganglionic pathway. From the nodes of the sympathetic trunk or (if there was no break there) from the intermediate nodes, non-myelinated fibers of the postganglionic pathway depart, heading to blood vessels and entrails.

Since the sympathetic part has a somatic part, it is connected to the spinal nerves that provide innervation to the soma. This connection is carried out through the gray connecting branches, rami communicantes grisei, which represent a section of postganglionic fibers along the nodes of the sympathetic trunk to n. spinalis As part of the rami communicantes grisei and spinal nerves, postganglionic fibers distribute in the vessels, glands and muscles that lift the hair of the skin of the trunk and limbs, as well as in the skeletal muscles, providing its trophism and tone.

Thus, the sympathetic part is connected to the animal nervous system through two kinds of connecting branches: white and gray, rami communicantes albi et grisei. The white connecting branches (myelin) contain preganglionic fibers. They go from the centers of the sympathetic part through the anterior roots to the nodes of the sympathetic trunk. Since the centers lie at the level of the thoracic and upper lumbar segments, rami communicantes albi are present only in the range from the I thoracic to the III lumbar spinal nerve. Rami communicantes grisei, postganglionic fibers, provide vasomotor and trophic processes of the soma; they connect the sympathetic trunk with the spinal nerves along its entire length.

Cervical sympathetic trunk It also has connections with the cranial nerves. Consequently, all plexuses of the animal nervous system contain fibers of the sympathetic part in their bundles and nerve trunks, which emphasizes the unity of these systems.

Sympathetic trunk

Each of the two sympathetic trunks is divided into four sections: cervical, thoracic, lumbar (or abdominal) and sacral (or pelvic).

Cervical region extends from the base of the skull to the neck of the first rib; located behind the carotid arteries on the deep muscles of the neck. It consists of three cervical sympathetic nodes: superior, middle and inferior.

Ganglion cervicale superius is the largest node of the sympathetic trunk, having a length of about 20 mm and a width of 4-6 mm. It lies at the level of the II and part of the III cervical vertebrae behind the internal carotid artery and medial to the vagus.

Ganglion cervicale medium is small in size, usually located at the intersection of a. The thyroidea inferior with the carotid artery is often absent or can split into two nodules.

Ganglion cervicale inferius is quite significant in size, located behind the initial part of the vertebral artery; often merges with the I and sometimes II thoracic node, forming a common cervicothoracic, or stellate, node, ganglion cervicothoracicum s. ganglion stellatum. From cervical nodes Nerves for the head, neck and chest come off. They can be divided into an ascending group, going to the head, a descending group, going down to the heart, and a group for the organs of the neck. The nerves to the head arise from the superior and inferior cervical ganglia and are divided into a group that penetrates the cranial cavity and a group that approaches the head from the outside. The first group is represented by n. caroticus interims, extending from the superior cervical ganglion, and n. vertebralis, extending from the lower cervical ganglion. Both nerves, accompanying the arteries of the same name, form plexuses around them: plexus caroticus interims and plexus vertebralis; together with the arteries, they penetrate into the cranial cavity, where they anastomose with each other and give branches to the brain vessels, meninges, pituitary gland, trunks of the III, IV, V, VI pairs of cranial nerves and the tympanic nerve.

Plexus caroticus intemus continues into the plexus cavernosus, which surrounds a. carotis interna in the area where it passes through the sinus cavernosus. The branches of the plexuses extend, in addition to the innermost carotid artery, also along its branches. Of the branches of the plexus caroticus internus, it should be noted n. petrosus profundus, which joins n. petrosus major and together with it forms n. canalis pterygoidei, approaching the ganglion pterygopalatinum through the canal of the same name.

The second group of sympathetic nerves of the head, external, is made up of two branches of the superior cervical ganglion, nn. carotid externi, which, having formed a plexus around the external carotid artery, accompany its branches on the head. From this plexus a stem extends to the ear node, gangl. oticum; from the plexus accompanying facial artery, a branch extends to the submandibular ganglion, gangl. submandibulare. Through the branches entering the plexuses around the carotid artery and its branches, the superior cervical node supplies fibers to the vessels (vasoconstrictors) and glands of the head: sweat, lacrimal, mucous and salivary, as well as to the hair muscles of the skin and to the muscle that dilates the pupil, m . dilatator pupillae.

The center of pupil dilation, centrum ciliospinale, is located in the spinal cord at the level from the VIII cervical to the II thoracic segment. The organs of the neck receive nerves from all three cervical ganglia; in addition, some of the nerves arise from the internodal areas of the cervical sympathetic trunk, and some from the plexuses of the carotid arteries. Branches from the plexuses follow the course of the branches of the external carotid artery, bear the same names and together with them approach the organs, due to which the number of individual sympathetic plexuses is equal to the number of arterial branches. Of the nerves extending from the cervical part of the sympathetic trunk, the laryngopharyngeal branches from the upper cervical ganglion are noted - rami laryngopharyngei, which partly go with n. laryngeus superior (branch of n. vagi) to the larynx, partly descending to the lateral wall of the pharynx; here they are together with the branches of the glossopharyngeal, vagus and superior laryngeal nerves form the pharyngeal plexus, plexus pharyngeus.

The descending group of branches of the cervical part of the sympathetic trunk is represented by nn. cardiaci cervicales superior, medius et inferior, extending from the corresponding cervical nodes. The cervical cardiac nerves descend into the chest cavity, where, together with the sympathetic thoracic cardiac nerves and branches of the vagus nerve, they participate in the formation of the cardiac plexuses.

Thoracic sympathetic trunk located in front of the necks of the ribs, covered in front by the pleura. It consists of 10-12 nodes of more or less triangular shape. The thoracic region is characterized by the presence of white connecting branches, rami communicantes albi, connecting the anterior roots of the spinal nerves with the nodes of the sympathetic trunk. Branches of the thoracic region:

1. Nn. cardiaci thoracici arise from the upper thoracic nodes and participate in the formation of the plexus cardlacus;
2. rami communicantes grisei, unmyelinated - to the intercostal nerves (somatic part of the sympathetic department);
3. rami pulmonales - to the lungs, forming plexus pulmonalis;
4. rami aortici form a plexus on thoracic aorta, plexus aorticus thoracicus, and partly on the esophagus, plexus esophageus, as well as on the thoracic duct (n. vagus also takes part in all of these plexuses);
5. nn. splanchnici major et minor, large and small splanchnic nerves; n. splanchnicus major begins with several roots extending from the V-IX thoracic nodes; roots n. splanchnicus major go in the medial direction and merge at the level of the IX thoracic vertebra into one common trunk, penetrating through the gap between the muscle bundles of the legs of the diaphragm in abdominal cavity, where it is part of the plexus coeliacus; n. splanchnicus minor starts from the X-XI thoracic nodes and also enters the plexus coeliacus, penetrating the diaphragm with the greater splanchnic nerve.

Vasoconstrictor fibers pass through these nerves, as can be seen from the fact that when these nerves are cut, the intestinal vessels are greatly filled with blood; in nn. splanchnici contains fibers that inhibit the movement of the stomach and intestines, as well as fibers that serve as conductors of sensations from the insides (afferent fibers of the sympathetic part).

Lumbar, or abdominal, section of the sympathetic trunk consists of four, sometimes three nodes. Sympathetic trunks in lumbar region located at a closer distance from one another than in the thoracic cavity, so that the nodes lie on the anterolateral surface of the lumbar vertebrae along the medial edge of m. psoas major.

Rami communicdntes albi are present with only two or three upper lumbar nerves. A large number of branches extend from the abdominal section of the sympathetic trunk along its entire length, which, together with the nn. splanchnici major et minor and the abdominal sections of the vagus nerves form the largest unpaired celiac plexus, plexus coeliacus. Numerous spinal nodes (C5-L3) and the axons of their neurocytes also participate in the formation of the celiac plexus. It lies on the anterior semicircle of the abdominal aorta, behind the pancreas, and surrounds the initial parts celiac trunk(truncus coeliacus) and superior mesenteric artery.

The plexus occupies the area between renal arteries, adrenal glands and aortic opening of the diaphragm and includes the paired celiac ganglion, ganglion coeliacum, and sometimes the unpaired superior mesenteric ganglion, ganglion mesentericum superius. A number of smaller paired plexuses extend from the celiac plexus to the diaphragm, adrenal glands, daughters, as well as the plexus testicularis (ovaricus), following the course of the arteries of the same name.

There are also a number of unpaired plexuses to individual organs along the walls of the arteries, the name of which they bear. Of the latter, the superior mesenteric plexus, plexus mesentericus superior, innervates the pancreas, small and large intestines up to half the length of the transverse colon. The second main source of innervation of the organs of the abdominal cavity is the plexus on the aorta, plexus aorticus abdominalis, composed of two trunks extending from the celiac plexus and branches from the lumbar nodes of the sympathetic trunk.

The inferior mesenteric plexus, plexus mesentericus inferior, departs from the aortic plexus for the transverse and descending part colon, sigmoid and upper parts of the rectum (plexus rectals superior). At the origin of the plexus mesentericus inferior there is a node of the same name, gangl. mesentericum inferius. Its postganglionic fibers run in the pelvis as part of the nn. Hypogastrici. The aortic plexus initially continues into the unpaired superior hypogastric plexus, plexus hypogastricus superior, which bifurcates at the promontory and passes into the pelvic plexus, or inferior hypogastric plexus (plexus hypogastricus inferior s. plexus pelvinus).

Fibers originating from the upper lumbar segments are vasomotor (vasoconstrictor) for the penis, motor for the uterus and bladder sphincter. The sacral, or pelvic, section usually has four nodes; located on the anterior surface of the sacrum along the medial edge of the anterior sacral foramina, both trunks gradually approach each other downwards and then end in one common unpaired node - ganglion impar, located on the anterior surface of the coccyx.

The nodes of the pelvic region, as well as the lumbar, are interconnected not only by longitudinal, but also by transverse trunks. From nodes sacral region the sympathetic trunk gives off a number of branches that connect with branches that separate from the inferior mesenteric plexus and form a plate extending from the sacrum to the bladder; this is the so-called lower hypogastric, or pelvic, plexus, plexus hypogastricus inferior s. plexus pelvinus. The plexus has its own nodes - ganglia pelvina.

The plexus has several sections:

1. the anterior-inferior section, in which the top part, innervating the bladder - plexus vesicalis, and the lower one, supplying in men prostate gland(plexus prostaticus), seminal vesicles and vas deferens (plexus deferentialis) and cavernous bodies (nn. cavernosi penis);
2. the posterior section of the plexus supplies the rectum (plexus rectales medii et inferiores).

In women, there is also a middle section, the lower part of which gives branches to the uterus and vagina (plexus uterovaginal), cavernous bodies of the clitoris (nn. cavernosi clitoridis), and the upper part - to the uterus and ovaries. Connecting branches, rami communicantes, depart from the nodes of the sacral section of the sympathetic trunk, joining the spinal nerves innervating the lower limb. These connecting branches constitute the somatic part of the sympathetic division of the autonomic nervous system, innervating the lower limb.

The rami communicantes and spinal nerves of the lower limb contain postganglionic fibers that distribute in the vessels, glands and hair muscles of the skin, as well as in the skeletal muscles, providing its trophism and tone.