The autonomic (autonomic, visceral) nervous system is an integral part of the human nervous system. Its main function is to ensure the functioning of internal organs. It consists of two departments, sympathetic and parasympathetic, which provide opposite effects on human organs. The work of the autonomic nervous system is very complex and relatively autonomous, almost not subject to human will. Let's take a closer look at the structure and functions of the sympathetic and parasympathetic divisions of the autonomic nervous system.
Concept of the autonomic nervous system
The autonomic nervous system consists of nerve cells and their processes. Like the normal human nervous system, the autonomic nervous system has two divisions:
- central;
- peripheral.
The central part exercises control over the functions of internal organs; this is the management department. There is no clear division into parts that are opposite in their sphere of influence. He is always involved in work, around the clock.
The peripheral part of the autonomic nervous system is represented by the sympathetic and parasympathetic divisions. The structures of the latter are found in almost every internal organ. Departments work simultaneously, but, depending on what is currently required from the body, one of them turns out to be predominant. It is the multidirectional influences of the sympathetic and parasympathetic departments that allow the human body to adapt to constantly changing environmental conditions.
Functions of the autonomic nervous system:
- maintaining a constant internal environment (homeostasis);
- ensuring all physical and mental activity of the body.
Do you have any physical activity coming up? With the help of the autonomic nervous system, blood pressure and cardiac activity will ensure sufficient minute volume of blood circulation. Are you on vacation and have frequent heart contractions? The visceral (autonomic) nervous system will cause the heart to beat more slowly.
What is the autonomic nervous system and where is “it” located?
Central department
This part of the autonomic nervous system represents various structures of the brain. It turns out that it is scattered throughout the entire brain. In the central section, segmental and suprasegmental structures are distinguished. All formations belonging to the suprasegmental department are united under the name hypothalamic-limbic-reticular complex.
Hypothalamus
The hypothalamus is a structure of the brain located in the lower part, at the base. This cannot be said to be an area with clear anatomical boundaries. The hypothalamus smoothly passes into the brain tissue of other parts of the brain.
In general, the hypothalamus consists of a cluster of groups of nerve cells, nuclei. A total of 32 pairs of nuclei were studied. Nerve impulses are formed in the hypothalamus, which reach other brain structures through various pathways. These impulses control blood circulation, breathing, and digestion. The hypothalamus contains centers for regulating water-salt metabolism, body temperature, sweating, hunger and satiety, emotions, and sexual desire.
In addition to nerve impulses, substances with a hormone-like structure are formed in the hypothalamus: releasing factors. With the help of these substances, the activity of the mammary glands (lactation), adrenal glands, gonads, uterus, thyroid gland, growth, fat breakdown, and the degree of skin color (pigmentation) is regulated. All this is possible thanks to the close connection of the hypothalamus with the pituitary gland, the main endocrine organ of the human body.
Thus, the hypothalamus is functionally connected with all parts of the nervous and endocrine systems.
Conventionally, two zones are distinguished in the hypothalamus: trophotropic and ergotropic. The activity of the trophotropic zone is aimed at maintaining the constancy of the internal environment. It is associated with a period of rest, supports the processes of synthesis and utilization of metabolic products. It exerts its main influences through the parasympathetic division of the autonomic nervous system. Stimulation of this area of the hypothalamus is accompanied by increased sweating, salivation, slowing of heart rate, decreased blood pressure, vasodilation, and increased intestinal motility. The trophotropic zone is located in the anterior parts of the hypothalamus. The ergotropic zone is responsible for the body’s adaptability to changing conditions, ensures adaptation and is realized through the sympathetic division of the autonomic nervous system. At the same time, blood pressure increases, heartbeat and breathing accelerate, pupils dilate, blood sugar increases, intestinal motility decreases, and urination and bowel movements are inhibited. The ergotropic zone occupies the posterior parts of the hypothalamus.
Limbic system
This structure includes part of the temporal lobe cortex, hippocampus, amygdala, olfactory bulb, olfactory tract, olfactory tubercle, reticular formation, cingulate gyrus, fornix, and papillary bodies. The limbic system is involved in the formation of emotions, memory, thinking, ensures eating and sexual behavior, and regulates the sleep-wake cycle.
To realize all these influences, the participation of many nerve cells is necessary. The functioning system is very complex. In order for a certain model of human behavior to be formed, it is necessary to integrate many sensations from the periphery, transmitting excitation simultaneously to various structures of the brain, as if circulating nerve impulses. For example, in order for a child to remember the names of the seasons, repeated activation of structures such as the hippocampus, fornix, and papillary bodies is necessary.
Reticular formation
This part of the autonomic nervous system is called the reticular system because, like a network, it interweaves all the structures of the brain. This diffuse location allows it to participate in the regulation of all processes in the body. The reticular formation keeps the cerebral cortex in good shape, in constant readiness. This ensures instant activation of the desired areas of the cerebral cortex. This is especially important for the processes of perception, memory, attention and learning.
Individual structures of the reticular formation are responsible for specific functions in the body. For example, there is a respiratory center, which is located in the medulla oblongata. If it is affected for any reason, then independent breathing becomes impossible. By analogy, there are centers of cardiac activity, swallowing, vomiting, coughing, and so on. The functioning of the reticular formation is also based on the presence of numerous connections between nerve cells.
In general, all structures of the central part of the autonomic nervous system are interconnected through multineuron connections. Only their coordinated activity allows the vital functions of the autonomic nervous system to be realized.
Segmental structures
This part of the central part of the visceral nervous system has a clear division into sympathetic and parasympathetic structures. Sympathetic structures are located in the thoracolumbar region, and parasympathetic structures are located in the brain and sacral spinal cord.
Sympathetic department
Sympathetic centers are localized in the lateral horns in the following segments of the spinal cord: C8, all thoracic (12), L1, L2. Neurons in this area are involved in the innervation of smooth muscles of internal organs, internal muscles of the eye (regulation of pupil size), glands (lacrimal, salivary, sweat, bronchial, digestive), blood and lymphatic vessels.
Parasympathetic Division
Contains the following structures in the brain:
- accessory nucleus of the oculomotor nerve (nucleus of Yakubovich and Perlia): control of pupil size;
- lacrimal nucleus: accordingly, regulates tear secretion;
- superior and inferior salivary nuclei: provide saliva production;
- dorsal nucleus of the vagus nerve: provides parasympathetic influences on internal organs (bronchi, heart, stomach, intestines, liver, pancreas).
The sacral section is represented by neurons of the lateral horns of segments S2-S4: they regulate urination and defecation, blood flow to the vessels of the genital organs.
Peripheral department
This section is represented by nerve cells and fibers located outside the spinal cord and brain. This part of the visceral nervous system accompanies the vessels, weaving around their wall, and is part of the peripheral nerves and plexuses (related to the normal nervous system). The peripheral department also has a clear division into the sympathetic and parasympathetic parts. The peripheral department ensures the transfer of information from the central structures of the visceral nervous system to the innervated organs, that is, it carries out the implementation of what is “planned” in the central autonomic nervous system.
Sympathetic department
Represented by the sympathetic trunk, located on both sides of the spine. The sympathetic trunk is two rows (right and left) of nerve ganglia. The nodes are connected to each other in the form of bridges, moving between parts of one side and the other. That is, the trunk looks like a chain of nerve lumps. At the end of the spine, two sympathetic trunks unite into one unpaired coccygeal ganglion. In total, there are 4 sections of the sympathetic trunk: cervical (3 nodes), thoracic (9-12 nodes), lumbar (2-7 nodes), sacral (4 nodes and plus one coccygeal).
The cell bodies of neurons are located in the area of the sympathetic trunk. Fibers from the nerve cells of the lateral horns of the sympathetic part of the central part of the autonomic nervous system approach these neurons. The impulse can switch on the neurons of the sympathetic trunk, or it can transit and switch on intermediate nodes of nerve cells located either along the spine or along the aorta. Subsequently, the fibers of the nerve cells, after switching, form weaves in the nodes. In the neck area it is the plexus around the carotid arteries, in the chest cavity it is the cardiac and pulmonary plexuses, in the abdominal cavity it is the solar (celiac), superior mesenteric, inferior mesenteric, abdominal aortic, superior and inferior hypogastric. These large plexuses are divided into smaller ones, from which autonomic fibers move to the innervated organs.
Parasympathetic Division
Represented by nerve ganglia and fibers. The peculiarity of the structure of this department is that the nerve nodes in which the impulse switches occur are located directly next to the organ or even in its structures. That is, the fibers coming from the “last” neurons of the parasympathetic department to the innervated structures are very short.
From the central parasympathetic centers located in the brain, impulses go as part of the cranial nerves (oculomotor, facial and trigeminal, glossopharyngeal and vagus, respectively). Since the vagus nerve is involved in the innervation of internal organs, its fibers reach the pharynx, larynx, esophagus, stomach, trachea, bronchi, heart, liver, pancreas, and intestines. It turns out that most internal organs receive parasympathetic impulses from the branching system of just one nerve: the vagus.
From the sacral sections of the parasympathetic part of the central visceral nervous system, nerve fibers go as part of the pelvic splanchnic nerves and reach the pelvic organs (bladder, urethra, rectum, seminal vesicles, prostate gland, uterus, vagina, part of the intestine). In the walls of organs, the impulse is switched in the nerve ganglia, and short nerve branches are in direct contact with the innervated area.
Metasympathetic division
It stands out as a separate separately existing department of the autonomic nervous system. It is detected mainly in the walls of internal organs that have the ability to contract (heart, intestines, ureter and others). It consists of micronodes and fibers that form a nerve plexus in the thickness of the organ. The structures of the metasympathetic autonomic nervous system can respond to both sympathetic and parasympathetic influences. But, in addition, their ability to work autonomously has been proven. It is believed that the peristaltic wave in the intestine is the result of the functioning of the metasympathetic autonomic nervous system, and the sympathetic and parasympathetic divisions only regulate the strength of peristalsis.
How do the sympathetic and parasympathetic divisions work?
The functioning of the autonomic nervous system is based on the reflex arc. A reflex arc is a chain of neurons in which a nerve impulse moves in a certain direction. This can be represented schematically as follows. At the periphery, the nerve ending (receptor) picks up any irritation from the external environment (for example, cold), and transmits information about the irritation to the central nervous system (including the autonomic one) along the nerve fiber. After analyzing the received information, the autonomic system makes a decision on the response actions required by this irritation (you need to warm up so that it is not cold). From the suprasegmental parts of the visceral nervous system, the “decision” (impulse) is transmitted to the segmental parts in the brain and spinal cord. From the neurons of the central sections of the sympathetic or parasympathetic part, the impulse moves to peripheral structures - the sympathetic trunk or nerve nodes located near organs. And from these formations, the impulse along the nerve fibers reaches the immediate organ - the implementer (in the case of a feeling of cold, a contraction of smooth muscles in the skin occurs - “goosebumps”, “goose bumps”, the body tries to warm up). The entire autonomic nervous system functions according to this principle.
Law of Opposites
Ensuring the existence of the human body requires the ability to adapt. Different situations may require opposite actions. For example, when it’s hot you need to cool down (sweating increases), and when it’s cold you need to warm up (sweating is blocked). The sympathetic and parasympathetic sections of the autonomic nervous system have opposite effects on organs and tissues; the ability to “turn on” or “turn off” one or another influence allows a person to survive. What effects does activation of the sympathetic and parasympathetic divisions of the autonomic nervous system cause? Let's find out.
Sympathetic innervation provides:
Parasympathetic innervation acts as follows:
- constriction of the pupil, narrowing of the palpebral fissure, “retraction” of the eyeball;
- increased salivation, there is a lot of saliva and it is liquid;
- reduction in heart rate;
- decreased blood pressure;
- narrowing of the bronchi, increased mucus in the bronchi;
- decreased breathing rate;
- increased peristalsis up to intestinal spasms;
- increased secretion of the digestive glands;
- causes erection of the penis and clitoris.
There are exceptions to the general pattern. There are structures in the human body that have only sympathetic innervation. These are the walls of blood vessels, sweat glands and the adrenal medulla. Parasympathetic influences do not apply to them.
Typically, in the body of a healthy person, the influences of both departments are in a state of optimal balance. There may be a slight predominance of one of them, which is also a variant of the norm. The functional predominance of excitability of the sympathetic department is called sympathicotonia, and the parasympathetic department is called vagotonia. Some periods of human age are accompanied by an increase or decrease in the activity of both departments (for example, activity increases during adolescence, and decreases during old age). If there is a predominant role of the sympathetic department, then this is manifested by sparkle in the eyes, wide pupils, a tendency to high blood pressure, constipation, excessive anxiety and initiative. The vagotonic effect is manifested by narrow pupils, a tendency to low blood pressure and fainting, indecision, and excess body weight.
Thus, from the above it becomes clear that the autonomic nervous system with its oppositely directed sections ensures human life. Moreover, all structures work in harmony and coordination. The activity of the sympathetic and parasympathetic departments is not controlled by human thinking. This is exactly the case when nature turned out to be smarter than man. We have the opportunity to engage in professional activities, think, create, leave ourselves time for small weaknesses, being confident that our own body will not let us down. Internal organs will work even when we are resting. And this is all thanks to the autonomic nervous system.
Educational film “The Autonomic Nervous System”
13.1. GENERAL PROVISIONS
The autonomic nervous system can be considered as a complex of structures that make up the peripheral and central parts of the nervous system, providing regulation of the functions of organs and tissues, aimed at maintaining a relative constancy of the internal environment in the body (homeostasis). In addition, the autonomic nervous system is involved in the implementation of adaptive-trophic influences, as well as various forms of physical and mental activity.
The structures of the autonomic nervous system that make up the brain and spinal cord constitute its central section, the rest are peripheral. In the central section, it is customary to distinguish suprasegmental and segmental vegetative structures. Suprasegmental include areas of the cerebral cortex (mainly located mediobasally), as well as some formations of the diencephalon, primarily the hypothalamus. Segmental structures of the central part of the autonomic nervous system located in the brain stem and spinal cord. In the peripheral nervous system its vegetative part is represented by vegetative nodes, trunks and plexuses, afferent and efferent fibers, as well as vegetative cells and fibers located in structures that are usually considered animal (spinal gangls, nerve trunks, etc.), although in fact they have a mixed character.
Among the suprasegmental vegetative formations, the hypothalamic part of the diencephalon is of particular importance, the function of which is largely controlled by other brain structures, including the cerebral cortex. The hypothalamus ensures the integration of the functions of the animal (somatic) and the phylogenetically more ancient autonomic nervous system.
The autonomic nervous system is also known as autonomous due to its certain, albeit relative, autonomy, or visceral due to the fact that through it the regulation of the functions of internal organs is carried out.
13.2. HISTORY OF THE ISSUE
The first information about the structures and functions of vegetative structures is associated with the name of Galen (c. 130-c. 200), since it was he who studied the cranial nerves
you described the vagus nerve and the borderline trunk, which he called sympathetic. In the book “Structure of the Human Body” by A. Vesalius (1514-1564), published in 1543, an image of these formations is given and the ganglia of the sympathetic trunk are described.
In 1732, J. Winslow (Winslow J., 1669-1760) identified three groups of nerves, the branches of which, exerting a friendly influence on each other (“sympathy”), extend to the internal organs. The term “autonomic nervous system” was introduced in 1807 by the German physician I. Reill to designate the nervous structures that regulate the function of internal organs. French anatomist and physiologist M.F. Bicha (Bicha M.F., 1771-1802) believed that sympathetic nodes scattered in different parts of the body act independently (autonomously) and from each of them there are branches that connect them to each other and ensure their influence on the internal organs. In 1800 he also proposed division of the nervous system into vegetative (plant) and animal (animal). In 1852, the French physiologist Claude Bernard (1813-1878) proved that irritation of the cervical sympathetic nerve trunk leads to vasodilation, thus describing the vasomotor function of the sympathetic nerves. He also established that an injection of the bottom of the fourth ventricle of the brain (“sugar injection”) changes the state of carbohydrate metabolism in the body.
At the end of the 19th century. English physiologist J. Langley (Langley J.N., 1852-1925) coined the term "autonomic nervous system" noting that the word "autonomous" no doubt indicates a greater degree of independence from the central nervous system than is actually the case. Based on morphological differences, as well as signs of functional antagonism of individual vegetative structures, J. Langley identified sympathetic And parasympathetic divisions of the autonomic nervous system. He also proved that in the central nervous system there are centers of the parasympathetic nervous system in the midbrain and medulla oblongata, as well as in the sacral segments of the spinal cord. In 1898, J. Langley established in the peripheral part of the autonomic nervous system (on the way from the structures of the central nervous system to the working organ) the presence of synaptic devices located in the vegetative nodes, in which the efferent nerve impulses are switched from neuron to neuron. He noted that the peripheral part of the autonomic nervous system contains preganglionic and postganglionic nerve fibers and quite accurately described the general structure of the autonomic (autonomic) nervous system.
In 1901, T. Elliott suggested the chemical transmission of nerve impulses in the vegetative nodes, and in 1921, in the process of experimental studies, this position was confirmed by the Austrian physiologist O. Loewi (Loewi O., 1873-1961) and , thus, laid the foundation for the doctrine of mediators (neurotransmitters). In 1930, the American physiologist W. Cannon(Cannon W., 1871-1945), studying the role of the humoral factor and autonomic mechanisms in maintaining the relative constancy of the internal environment of the body, coined the term"homeostasis" and in 1939 he established that if in the functional series of neurons in one of the links the movement of nerve impulses is interrupted, then the resulting general or partial denervation of subsequent links in the chain causes an increase in the sensitivity of all receptors located in them to the excitatory or inhibitory action
chemical substances (including medications) with properties similar to the corresponding mediators (Cannon-Rosenbluth law).
The role of the German physiologist E. Hering (Hering E., 1834-1918), who discovered the sinocarotid reflexes, and the domestic physiologist L.A., in the knowledge of the functions of the autonomic nervous system, is significant. Orbeli (1882-1958), who created the theory of the adaptive-trophic influence of the sympathetic nervous system. Many clinical neurologists, including our compatriots M.I., contributed to the expansion of ideas about the clinical manifestations of damage to the autonomic nervous system. Astvatsaturov, G.I. Markelov, N.M. Itsenko, I.I. Rusetsky, A.M. Grinstein, N.I. Grashchenkov, N.S. Chetverikov, A.M. Wayne.
13.3. STRUCTURE AND FUNCTIONS OF THE AUTONOMIC NERVOUS SYSTEM
Taking into account the peculiarities of the structure and function of the segmental part of the autonomic nervous system, it is mainly distinguished sympathetic and parasympathetic divisions (Fig. 13.1). The first of them provides mainly catabolic processes, the second - anabolic. Composed of the sympathetic and parasympathetic divisions of the autonomic nervous system includes both afferent and efferent, as well as intercalary structures. Already on the basis of these data, it is possible to outline a scheme for constructing an autonomic reflex.
13.3.1. Arc of the autonomic reflex (principles of construction)
The presence of afferent and efferent sections of the autonomic nervous system, as well as associative (intercalary) formations between them, ensures the formation of autonomic reflexes, the arcs of which are closed at the spinal or cerebral level. Their afferent link is represented by receptors (mainly chemoreceptors) located in almost all organs and tissues, as well as by vegetative fibers extending from them - the dendrites of the first sensitive autonomic neurons, which ensure the conduction of autonomic impulses in a centripetal direction to the bodies of these neurons located in the spinal column. brain ganglia or their analogues located in the cranial nerves. Next, autonomic impulses, following the axons of the first sensory neurons through the dorsal spinal roots, enter the spinal cord or brain and end at the intercalary (associative) neurons that are part of the segmental autonomic centers of the spinal cord or brain stem. association neurons, in turn, they have numerous vertical and horizontal intersegmental connections and are under the control of suprasegmental vegetative structures.
Efferent part of the arc of autonomic reflexes consists of preganglionic fibers, which are axons of cells of the autonomic centers (nuclei) of the segmental part of the central nervous system (brain stem, spinal
Rice. 13.1.Autonomic nervous system.
1 - cerebral cortex; 2 - hypothalamus; 3 - ciliary node; 4 - pterygopalatine node; 5 - submandibular and sublingual nodes; 6 - ear node; 7 - superior cervical sympathetic node; 8 - great splanchnic nerve; 9 - internal node; 10 - celiac plexus; 11 - celiac nodes; 12 - small internal
nerve; 13, 14 - superior mesenteric plexus; 15 - inferior mesenteric plexus; 16 - aortic plexus; 17 - pelvic nerve; 18 - hypogastric plexus; 19 - ciliary muscle, 20 - sphincter of the pupil; 21 - pupil dilator; 22 - lacrimal gland; 23 - glands of the nasal mucosa; 24 - submandibular gland; 25 - sublingual gland; 26 - parotid gland; 27 - heart; 28 - thyroid gland; 29 - larynx; 30 - muscles of the trachea and bronchi; 31 - lung; 32 - stomach; 33 - liver; 34 - pancreas; 35 - adrenal gland; 36 - spleen; 37 - kidney; 38 - large intestine; 39 - small intestine; 40 - bladder detrusor; 41 - sphincter of the bladder; 42 - gonads; 43 - genitals.
brain), which leave the brain as part of the anterior spinal roots and reach certain peripheral autonomic ganglia. Here, vegetative impulses are switched to neurons whose bodies are located in ganglia and then along postganglionic fibers, which are the axons of these neurons, to the innervated organs and tissues.
13.3.2. Afferent structures of the autonomic nervous system
The morphological substrate of the afferent part of the peripheral part of the autonomic nervous system does not have any fundamental differences from the afferent part of the peripheral part of the animal nervous system. The bodies of the first sensory autonomic neurons are located in the same spinal ganglia or their analogues in the ganglia of the cranial nerves, which also contain the first neurons of the animal sensory pathways. Consequently, these nodes are animal-vegetative (somato-vegetative) formations, which can be considered as one of the facts indicating the unclear delineation of the boundaries between the animal and autonomic structures of the nervous system.
The bodies of the second and subsequent sensory autonomic neurons are located in the spinal cord or in the brain stem; their processes have contacts with many structures of the central nervous system, in particular with the nuclei of the diencephalon, primarily the thalamus and hypothalamus, as well as with other parts of the brain included in the limbic system. reticular complex. In the afferent part of the autonomic nervous system, one can note an abundance of receptors (interoreceptors, visceroreceptors) located in almost all organs and tissues.
13.3.3. Efferent structures of the autonomic nervous system
If the structure of the afferent part of the autonomic and animal parts of the nervous system can be very similar, then the efferent part of the autonomic nervous system is characterized by very significant morphological features, while they are not identical in its parasympathetic and sympathetic parts.
13.3.3.1. The structure of the efferent part of the parasympathetic division of the autonomic nervous system
The central division of the parasympathetic nervous system is divided into three parts: mesencephalic, bulbar and sacral.
Mesencephalic part make up pairs parasympathetic nuclei of Yakubovich-Westphal-Edinger, related to the system of oculomotor nerves. Peripheral part mesencephalic division of the peripheral nervous system consists of axons of this nucleus, constituting the parasympathetic portion of the oculomotor nerve, which penetrates through the superior orbital fissure into the orbital cavity, with preganglionic parasympathetic fibers included in it reach located in the tissue of the orbit ciliary node (ganglion ciliare), in which nerve impulses switch from neuron to neuron. The postganglionic parasympathetic fibers emerging from it participate in the formation of short ciliary nerves (nn. ciliares breves) and end in the smooth muscles innervated by them: in the muscle that constricts the pupil (m. sphincter pupille), and in the ciliary muscle (m. ciliaris ), reduction of which provides accommodation of the lens.
TO bulbar part The parasympathetic nervous system includes three pairs of parasympathetic nuclei - the superior salivary, inferior salivary and dorsal. The axons of the cells of these nuclei constitute the parasympathetic portions of the intermediate nerve of Wriesberg (running part of the way as part of the facial nerve), glossopharyngeal and vagus nerves. These parasympathetic structures of these cranial nerves consist of preganglionic fibers, which end in the vegetative nodes. In the system of the intermediate and glossopharyngeal nerves This pterygopalatine (g. pterygopalatum), ear (g. oticum), sublingual and submandibular nodes(g. sublingualis And g. submandibularis). Originating from these parasympathetic nodes postganglionic nervous fibers reach innervated by them lacrimal gland, salivary glands and mucous glands of the nasal and oral cavity.
Axons of the dorsal parasympathetic nucleus of the vagus nerve emerge from the medulla oblongata in its composition, leaving, Thus, the cranial cavity through the jugular foramen. After this, they end in numerous autonomic nodes of the vagus nerve system. Already at the level of the jugular foramen, where the two nodes of this nerve (superior and inferior), part of the preganglionic fibers ends in them. Subsequently, postganglionic fibers depart from the superior ganglion, forming meningeal branches, involved in the innervation of the dura mater, and auricular branch; departs from the inferior ganglion of the vagus nerve pharyngeal branch. Subsequently, other nerves are separated from the trunk of the vagus nerve. preganglionic fibers forming the cardiac depressive nerve and partly the recurrent laryngeal nerve; in the chest cavity they arise from the vagus nerve tracheal, bronchial and esophageal branches, in the abdominal cavity - anterior and posterior gastric and celiac. Preganglionic fibers innervating internal organs end in the parasympathetic periorgan and intraorgan (intramural) nodes,
located in the walls of internal organs or in close proximity to them. Postganglionic fibers arising from these nodes provide parasympathetic innervation of the thoracic and abdominal organs. The exciting parasympathetic influence on these organs has a slower effect.
slow heart rate, narrowing of the bronchial lumen, increased peristalsis of the esophagus, stomach and intestines, increased secretion of gastric and duodenal juice, etc.
Sacral part the parasympathetic nervous system makes up accumulations of parasympathetic cells in the gray matter of segments S II - S IV of the spinal cord. The axons of these cells leave the spinal cord as part of the anterior roots, then pass along the anterior branches of the sacral spinal nerves and are separated from them in the form pudendal nerves (nn. pudendi), who take part in the formation lower hypogastric plexus And are running out in intraorgan parasympathetic nodes of the pelvis. The organs in which these nodes are located are innervated by postganglionic fibers extending from them.
13.3.3.2. The structure of the efferent section of the sympathetic division of the autonomic nervous system
The central section of the sympathetic autonomic nervous system is represented by cells of the lateral horns of the spinal cord at the level from the VIII cervical to the III-IV lumbar segments. These autonomic cells collectively form the spinal sympathetic center, or columna intermedia (autonomica).
Components of the spinal sympathetic center Jacobson cells (small, multipolar) associated with higher vegetative centers, included in the system of the limbic-reticular complex, which, in turn, have connections with the cerebral cortex and are influenced by impulses emanating from the cortex. The axons of sympathetic Jacobson cells emerge from the spinal cord as part of the anterior spinal roots. Subsequently, passing through the intervertebral foramen as part of the spinal nerves, they fall into their white connecting branches (rami communicantes albi). Each white connecting branch enters one of the paravertebral (paravertebral) nodes that are part of the borderline sympathetic trunk. Here part of the fibers of the white connecting branch ends and forms synaptic contacts with the sympathetic cells of these nodes, the other part of the fibers passes through the paravertebral node in transit and reaches the cells of other nodes of the border sympathetic trunk or prevertebral (prevertebral) sympathetic ganglia.
The nodes of the sympathetic trunk (paravertebral nodes) are located in a chain on both sides of the spine, with internodal connecting branches passing between them (rami communicantes interganglionares), and thus are formed border sympathetic trunks (trunci sympathici dexter et sinister), consisting of a chain of 17-22 sympathetic nodes, between which there are transverse connections (tracti transversalis). The borderline sympathetic trunks extend from the base of the skull to the coccyx and have 4 sections: cervical, thoracic, lumbar and sacral.
Some of the cells deprived of the myelin sheath of axons located in the nodes of the border sympathetic trunk form gray connecting branches (rami communicantes grisei) and then enter the structures of the peripheral nervous system: as part of the anterior branch of the spinal nerve, nerve plexus and peripheral nerves, it approaches various tissues, providing their sympathetic innervation. This part carries out, in particular,
sympathetic innervation of the pilomotor muscles, as well as the sweat and sebaceous glands. Another part of the postganglionic fibers of the sympathetic trunk forms plexuses that spread along the blood vessels. The third part of the postganglionic fibers, together with the preganglionic fibers that pass by the ganglia of the sympathetic trunk, form sympathetic nerves, which go mainly to the internal organs. Along the way, the preganglionic fibers included in their composition end in the prevertebral sympathetic ganglia, from which postganglionic fibers involved in the innervation of organs and tissues also depart. Cervical sympathetic trunk:
1) Cervical sympathetic nodes - top, middle and bottom. Upper cervical knot (gangl. cervicale superius) located near the occipital bone at the level of the first three cervical vertebrae along the dorsomedial surface of the internal carotid artery. Middle cervical node (gangl. cervicale medium) unstable, located at the level of the IV-VI cervical vertebrae, in front of the subclavian artery, medial to the 1st rib. Lower cervical knot (gangl. cervicale inferior) in 75-80% of people it merges with the first (less often with the second) thoracic node, and a large one is formed cervicothoracic node (gangl. cervicothoracicum), or so called star knot (gangl. stellatum).
At the cervical level of the spinal cord there are no lateral horns and vegetative cells; therefore, the preganglionic fibers going to the cervical ganglia are axons of sympathetic cells, the bodies of which are located in the lateral horns of the four or five upper thoracic segments; they enter the cervicothoracic ( stellate) node. Some of these axons end in this node, and the nerve impulses traveling along them are switched here to the next neuron. The other part passes through the node of the sympathetic trunk in transit and the impulses traveling along them are switched to the next sympathetic neuron in the upper middle or upper cervical sympathetic node.
Postganglionic fibers extending from the cervical nodes of the sympathetic trunk give off branches that provide sympathetic innervation to the organs and tissues of the neck and head. Postganglionic fibers arising from the superior cervical ganglion form the plexuses of the carotid arteries, controlling the tone of the vascular wall of these arteries and their branches, as well as provide sympathetic innervation to the sweat glands, smooth muscle that dilates the pupil (m. dilatator pupillae), the deep plate of the muscle that lifts the upper eyelid (lamina profunda m. levator palpebrae superioris), and the orbital muscle (m. orbitalis). Branches involved in innervation also depart from the plexus of the carotid arteries lacrimal and salivary glands, hair follicles, thyroid artery, as well as those innervating the larynx and pharynx, which are involved in the formation of the superior cardiac nerve, which is part of the cardiac plexus.
From the axons of neurons located in the middle cervical sympathetic node, the middle cardiac nerve, involved in the formation of the cardiac plexus.
Postganglionic fibers arising from the inferior cervical sympathetic ganglion or formed in connection with its fusion with the superior thoracic ganglion of the cervicothoracic or stellate ganglion form the sympathetic plexus of the vertebral artery, also known as spinal nerve. This plexus surrounds the vertebral artery, passes with it through the bone canal formed by the openings in the transverse processes of the C VI-C II vertebrae and enters the cranial cavity through the foramen magnum.
2) The thoracic part of the paravertebral sympathetic trunk consists of 9-12 nodes. Each of them has a white connecting branch. Gray communicating branches go to all intercostal nerves. Visceral branches from the first four nodes are directed to the heart, lungs, pleura, where, together with the branches of the vagus nerve, they form the corresponding plexuses. Branches from 6-9 nodes form greater splanchnic nerve, which passes into the abdominal cavity and enters celiac node, being part of the celiac (solar) plexus complex (plexus coeliacus). The branches of the last 2-3 nodes of the sympathetic trunk form lesser splanchnic nerve, some of the branches of which branch in the adrenal and renal plexuses.
3) The lumbar part of the paravertebral sympathetic trunk consists of 2-7 nodes. White connecting branches only fit the first 2-3 nodes. The gray communicating branches extend from all lumbar sympathetic ganglia to the spinal nerves, and the visceral trunks form the abdominal aortic plexus.
4) Sacral part The paravertebral sympathetic trunk consists of four pairs of sacral and one pair of coccygeal ganglia. All these ganglia are connected to the sacral spinal nerves and give off branches to the organs and neurovascular plexuses of the pelvis.
Prevertebral sympathetic ganglia characterized by inconstancy of shape and size. Their accumulations and associated vegetative fibers form plexuses. Topographically, the prevertebral plexuses of the neck, thoracic, abdominal and pelvic cavities are distinguished. In the thoracic cavity the largest are the cardiac plexus, and in the abdominal cavity the largest are the celiac (solar), aortic, mesenteric, and hypogastric plexuses.
Of the peripheral nerves, the median and sciatic nerves, as well as the tibial nerve, are richest in sympathetic fibers. Their damage, usually traumatic, more often than damage to other peripheral nerves causes the occurrence of causalgia. The pain in causalgia is burning, extremely painful, difficult to localize, and tends to spread far beyond the zone innervated by the affected nerve, in which, by the way, severe hyperpathy is usually noted. Patients with causalgia are characterized by some relief of the condition and a decrease in pain when the innervation zone is moistened (wet rag symptom).
The sympathetic innervation of the tissues of the trunk and limbs, as well as internal organs, is segmental in nature, in this case, the zones of the segments do not correspond to metameres characteristic of somatic spinal innervation. Sympathetic segments (cells of the lateral horns of the spinal cord that make up the spinal sympathetic center) from C VIII to Th III provide sympathetic innervation to the tissues of the head and neck, segments Th IV - Th VII - tissues of the shoulder girdle and arm, segments Th VIII Th IX - torso; the lowest located segments, which contain lateral horns, Th X - Th III, provide sympathetic innervation to the organs of the pelvic girdle and legs.
Sympathetic innervation of internal organs is provided by autonomic fibers connected to certain segments of the spinal cord. Pain arising from damage to internal organs can radiate to the areas of the dermatomes corresponding to these segments (Zakharyin-Ged zones) . Such referred pain, or hyperesthesia, occurs as a viscerosensory reflex (Fig. 13.2).
Rice. 13.2.Zones of reflected pain (Zakharyin-Ged zones) on the torso in diseases of the internal organs are a viscerosensory reflex.
Vegetative cells are small in size, their fibers are pulpless or have a very thin myelin sheath, and belong to groups B and C. In this regard, the speed of transmission of nerve impulses in vegetative fibers is relatively low.
13.3.4. Metasympathetic division of the autonomic nervous system
In addition to the parasympathetic and sympathetic divisions, physiologists distinguish the metasympathetic division of the autonomic nervous system. This term refers to a complex of microganglionic formations located in the walls of internal organs that have motor activity (heart, intestines, ureters, etc.) and ensure their autonomy. The function of the nerve ganglia is to transmit central (sympathetic, parasympathetic) influences to the tissues, and, in addition, they ensure the integration of information arriving along local reflex arcs. Metasympathetic structures are independent formations capable of functioning with complete decentralization. Several (5-7) of the nearby nodes related to them are combined into a single functional module, the main units of which are oscillator cells that ensure the autonomy of the system, interneurons, motor neurons, and sensory cells. Individual functional modules form a plexus, thanks to which, for example, a peristaltic wave is organized in the intestine.
The functions of the metasympathetic division of the autonomic nervous system do not directly depend on the activity of the sympathetic or parasympathetic
nervous systems, but can be modified under their influence. For example, activation of the parasympathetic influence increases intestinal motility, and the sympathetic influence weakens it.
13.3.5. Suprasegmental vegetative structures
Strictly speaking, irritation of any part of the brain is accompanied by some kind of vegetative response, but in its supratentorial structures there are no compact territories that could be classified as specialized vegetative formations. However, there are suprasegmental vegetative structures of the cerebrum and diencephalon, having the most significant, primarily integrative, influence on the state of vegetative innervation of organs and tissues.
These structures include the limbic-reticular complex, primarily the hypothalamus, in which it is customary to distinguish the anterior - trophotropic and rear - ergotropic departments. Structures of the limbic-reticular complex have numerous direct and feedback connections with the new cortex (neocortex) of the cerebral hemispheres, which controls and to some extent corrects their functional state.
Hypothalamus and other parts of the limbic-reticular complex have a global regulatory effect on the segmental parts of the autonomic nervous system, create a relative balance between the activities of sympathetic and parasympathetic structures, aimed at maintaining a state of homeostasis in the body. In addition, the hypothalamic region of the brain, the amygdala complex, the old and ancient cortex of the mediobasal regions of the cerebral hemispheres, the hippocampal gyrus and other parts of the limbic-reticular complex carry out integration between autonomic structures, the endocrine system and the emotional sphere, influence the formation of motivations, emotions, memory, and behavior.
Pathology of suprasegmental formations can lead to multisystem reactions, in which autonomic disorders are only one component of a complex clinical picture.
13.3.6. Mediators and their influence on the state of vegetative structures
The conduction of impulses through synaptic apparatuses in both the central and peripheral nervous systems is carried out thanks to mediators, or neurotransmitters. In the central nervous system, mediators are numerous and their nature has not been studied in all synaptic connections. The mediators of peripheral nervous structures, in particular those related to the autonomic nervous system, have been better studied. It should also be noted that in the afferent (centripetal, sensitive) part of the peripheral nervous system, which consists mainly of pseudounipolar cells with their processes, there are no synaptic apparatuses. In the efferent structures (Table 13.1) of the animal (somatic) part of the peripheral nervous system, there are only nervous
Scheme 13.1.Sympathetic apparatus and mediators of the peripheral nervous system CNS - central nervous system; PNS - peripheral nervous system; PS - parasympathetic structures of the central nervous system; C - sympathetic structures of the central nervous system; a - somatic motor fiber; b - preganglionic autonomic fibers; c - postganglionic autonomic fibers; CIRCLE - synaptic devices; mediators: ACh - acetylcholine; NA - norepinephrine.
muscle synapses. The mediator that ensures the conduction of nerve impulses through these synapses is acetylcholine-H (ACh-H), synthesized in peripheral motor neurons located in the structures of the central nervous system, and coming from there along their axons with an axocurrent into synaptic vesicles located near the presynaptic membrane.
The efferent peripheral part of the autonomic nervous system consists of preganglionic fibers emerging from the central nervous system (brain stem, spinal cord), as well as autonomic ganglia, in which impulses are switched through the synaptic apparatus from preganglionic fibers to cells located in the ganglia. Subsequently, impulses along the axons extending from these cells (postganglionic fibers) reach a synapse, which ensures switching of the impulse from these fibers to the innervated tissue.
Thus, all vegetative impulses on the way from the central nervous system to the innervated tissue pass through the synaptic apparatus twice. The first of the synapses is located in the parasympathetic or sympathetic ganglion; the switching of the impulse here in both cases is provided by the same transmitter as in the animal neuromuscular synapse - acetylcholine-N (ACH-N). The second, parasympathetic and sympathetic, synapses in which impulses switch from the postganglionic fiber to the innervated structure are not identical in the released transmitter. For the parasympathetic department it is acetylcholine-M (AC-M), for the sympathetic department it is mainly norepinephrine (NA). This is of significant importance, since with the help of certain medications it is possible to influence the conduction of nerve impulses in the zone of their transition through the synapse. Such drugs include H- and M-cholinomimetics and H- and M-anticholinergics, as well as adrenergic agonists and adrenergic blockers. When prescribing these drugs, it is necessary to take into account their effect on synaptic structures and predict what kind of reaction to the administration of each of them should be expected.
The effect of a pharmaceutical drug can affect the function of synapses belonging to different parts of the nervous system if neurotransmission in them is provided by a mediator that is identical or similar in chemical structure. Thus, the introduction of ganglion blockers, which are H-anticholinergics, has a blocking effect on the conduction of impulses from the preganglionic fiber to the cell located in the ganglion in both the sympathetic and parasympathetic ganglia, and can also suppress the conduction of nerve impulses through the neuromuscular synapses of the animal part of the peripheral nervous system .
In some cases, it is possible to influence the conduction of impulses through a synapse by means that differently affect the conductivity of synaptic apparatuses. Thus, the cholinomimetic effect is exerted not only by the use of cholinomimetics, in particular acetylcholine, which, by the way, quickly disintegrates and is therefore rarely used in clinical practice, but also by anticholinesterase drugs from the group of cholinesterase inhibitors (prozerin, galantamine, calemin, etc. ), which leads to protection from the rapid destruction of ACh molecules entering the synaptic cleft.
The structures of the autonomic nervous system are characterized by the ability to actively respond to many chemical and humoral stimuli. This circumstance determines the lability of vegetative functions with the slightest changes in the chemical composition of tissues, in particular blood, under the influence of changes in endogenous and exogenous influences. It also allows you to actively influence the autonomic balance by introducing into the body certain pharmacological agents that improve or block the conduction of autonomic impulses through the synaptic apparatus.
The autonomic nervous system influences the vitality of the body (Table 13.1). It regulates the state of the cardiovascular, respiratory, digestive, genitourinary and endocrine systems, fluid media, and smooth muscles. At the same time, the vegetative system performs an adaptation-trophic function, regulates the body’s energy resources, providing Thus all types of physical and mental activities, preparing organs and tissues, including nervous tissue and striated muscles, for the optimal level of their activity and the successful performance of their inherent functions.
Table 13.1.Functions of the sympathetic and parasympathetic divisions of the autonomic nervous system
End of table. 13-1
* For most sweat glands, some blood vessels and skeletal muscles, the sympathetic transmitter is acetylcholine. The adrenal medulla is innervated by cholinergic sympathetic neurons.
During periods of danger and intense work, the autonomic nervous system is called upon to satisfy the increasing energy needs of the body and does this by increasing the activity of metabolic processes, increasing pulmonary ventilation, transferring the cardiovascular and respiratory systems to a more intense mode, changing the hormonal balance, etc.
13.3.7. Study of autonomic functions
Information about autonomic disorders and their localization can help resolve the issue of the nature and location of the pathological process. Sometimes identifying signs of autonomic imbalance is of particular importance.
Changes in the functions of the hypothalamus and other suprasegmental structures of the autonomic nervous system lead to generalized autonomic disorders. Damage to the autonomic nuclei in the brainstem and spinal cord, as well as the peripheral parts of the autonomic nervous system, is usually accompanied by the development of segmental autonomic disorders in a more or less limited part of the body.
When examining the autonomic nervous system, you should pay attention to the patient’s physique, the condition of his skin (hyperemia, pallor, sweating, greasiness, hyperkeratosis, etc.), its appendages (baldness, graying; fragility, dullness, thickening, deformation of nails); the severity of the subcutaneous fat layer, its distribution; condition of the pupils (deformation, diameter); lacrimation; salivation; function of the pelvic organs (urinary urgency, urinary incontinence, urinary retention, diarrhea, constipation). It is necessary to get an idea of the patient’s character, his prevailing mood, well-being, performance, degree of emotionality, ability to adapt to changes in external temperature.
tours. It is necessary to obtain information about the state of the patient’s somatic status (frequency, lability, pulse rhythm, blood pressure, headache, its nature, history of migraine attacks, functions of the respiratory, digestive and other systems), the state of the endocrine system, thermometry results, laboratory parameters . Pay attention to the presence of allergic manifestations in the patient (urticaria, bronchial asthma, angioedema, essential itching, etc.), angiotrophoneurosis, acroangiopathy, sympathalgia, manifestations of “sea sickness” when using transport, “bear sickness”.
A neurological examination may reveal anisocoria, dilation or constriction of the pupils that do not correspond to the available illumination, impaired reaction of the pupils to light, convergence, accommodation, total tendon hyperreflexia with possible expansion of reflexogenic zones, general motor reaction, changes in local and reflex dermographism.
Local dermographism is caused by slight streak irritation of the skin with a blunt object, for example the handle of a hammer, or the rounded end of a glass rod. Normally, with mild irritation of the skin, a white stripe appears on it after a few seconds. If the skin irritation is more intense, the resulting stripe on the skin is red. In the first case, local dermographism is white, in the second, local dermographism is red.
If both weak and more intense skin irritation causes the appearance of local white dermographism, we can talk about increased vascular tone of the skin. If, even with minimal line irritations of the skin, local red dermographism occurs, but white dermographism cannot be obtained, then this indicates a decreased tone of skin vessels, primarily precapillaries and capillaries. With a pronounced decrease in their tone, streak irritation of the skin not only leads to the appearance of local red dermographism, but also to the penetration of plasma through the walls of blood vessels. Then the occurrence of edematous, or urticarial, or elevated dermographism is possible (dermographismus elevatus).
Reflex or pain dermographism caused by streak irritation of the skin with the tip of a needle or pin. Its reflex arc closes in the segmental apparatus of the spinal cord. In response to painful stimulation, a red stripe 1-2 mm wide with narrow white edges normally appears on the skin, which lasts for several minutes.
If the spinal cord is damaged, then in areas of the skin, the autonomic innervation of which should be provided by the affected segments, and in the lower parts of the body, there is no reflex dermographism. This circumstance may help clarify the upper limit of the pathological focus in the spinal cord. Reflex dermographism disappears in areas innervated by the affected structures of the peripheral nervous system.
The condition may also have a certain topical diagnostic value pilomotor (muscle-hair) reflex. It can be caused by painful or cold irritation of the skin in the trapezius muscle (superior pilomotor reflex) or in the gluteal region (inferior pilomotor reflex). The response in this case is the appearance of a widespread pilomotor reaction in the form of “goose bumps” on the corresponding half of the body. The speed and intensity of the reaction indicates the degree
excitability of the sympathetic division of the autonomic nervous system. The arc of the pilomotor reflex closes in the lateral horns of the spinal cord. With transverse lesions of the spinal cord, causing the superior pilomotor reflex, it can be noted that the pilomotor reaction is observed no lower than the level of the dermatome corresponding to the upper pole of the pathological focus. When the inferior pilomotor reflex is evoked, goose bumps appear in the lower part of the body, spreading upward to the lower pole of the pathological focus in the spinal cord.
It should be borne in mind that the results of the study of reflex dermographism and pilomotor reflexes provide only indicative information about the topic of the pathological focus in the spinal cord. Clarification of the localization of the pathological focus may necessitate a more complete neurological examination and often additional examination methods (myelography, MRI scanning).
The identification of local sweating disorders may be of some importance for topical diagnosis. For this purpose, iodine-starch is sometimes used. Minor's test. The patient's body is lubricated with a solution of iodine in castor oil and alcohol (iodi puri 16.0; olei risini 100.0; spiriti aetylici 900.0). After the skin dries, it is powdered with starch. Then one of the methods is used, which usually causes increased sweating, while the sweaty areas of the skin darken, since the sweat that appears promotes the reaction of starch with iodine. To provoke sweating, three indicators are used that affect different parts of the autonomic nervous system - different parts of the efferent part of the sweating reflex arc. Taking 1 g of aspirin causes increased sweating, causing stimulation of the sweat center at the level of the hypothalamus. Warming the patient in a light bath mainly affects the spinal sweating centers. Subcutaneous administration of 1 ml of a 1% solution of pilocarpine provokes sweating, stimulating the peripheral endings of postganglionic autonomic fibers located in the sweat glands themselves.
To determine the degree of excitability of the neuromuscular synaptic apparatus in the heart, orthostatic and clinostatic tests can be performed. Orthostatic reflex occurs when the subject moves from a horizontal to a vertical position. Before the test and within the first minute after the patient moves to a vertical position, his pulse is measured. Normally, the heart rate increases by 10-12 beats per minute. Clinostatic test checked when the patient moves from a vertical to a horizontal position. The pulse is also measured before the test and during the first minute after the patient assumes a horizontal position. Normally, the heart rate slows down by 10-12 beats per minute.
Lewis test (triad) - a complex of sequentially developing vascular reactions to the intradermal injection of two drops of an acidified 0.01% histamine solution. The following reactions normally occur at the injection site: 1) a red dot (limited erythema) appears due to local expansion of the capillaries; 2) soon it appears on top of a white papule (blister), which arises as a result of increased permeability of skin blood vessels; 3) skin hyperemia develops around the papule due to the expansion of arterioles. The spread of erythema beyond the papule may be absent in the case of skin denervation, while during the first few days after the break of the peripheral nerve it may be preserved and disappears over time.
the phenomenon of degenerative changes in the nerve. The outer red ring surrounding the papule is usually absent in Riley-Day syndrome (familial dysautonomia). The test can also be used to determine vascular permeability and identify vegetative asymmetries. It was described by the English cardiologist Th. Lewis (1871-1945).
During the clinical examination of patients, other methods of studying the autonomic nervous system can be used, including the study of skin temperature, skin sensitivity to ultraviolet radiation, skin hydrophilicity, skin pharmacological tests with drugs such as adrenaline, acetylcholine and some other vegetotropic drugs, the study of electrodermal resistance, Danini-Aschner ocular reflex, capillaroscopy, plethysmography, autonomic plexus reflexes (cervical, epigastric), etc. The methodology for their implementation is described in special and reference manuals.
Studying the state of autonomic functions can provide important information about the presence of a functional or organic lesion of the nervous system in a patient, often helping to resolve the issue of topical and nosological diagnosis.
Identification of autonomic asymmetries that go beyond physiological fluctuations can be considered a sign of diencephalic pathology. Local changes in autonomic innervation can contribute to the topical diagnosis of certain diseases of the spinal cord and peripheral nervous system. Soreness and vegetative disorders in the Zakharyin-Ged zones, which are reflected in nature, may indicate the pathology of one or another internal organ. Signs of increased excitability of the autonomic nervous system and autonomic lability can be objective confirmation of the presence of neurosis or a neurosis-like condition in the patient. Their identification sometimes plays a very important role in the professional selection of people to work in certain specialties.
The results of studying the state of the autonomic nervous system to some extent make it possible to judge the mental status of a person, primarily his emotional sphere. Such research underlies the discipline that combines physiology and psychology and is known as psychophysiology, confirming the relationship between mental activity and the state of the autonomic nervous system.
13.3.8. Some clinical phenomena depending on the state of the central and peripheral structures of the autonomic nervous system
The functions of all organs and tissues and, consequently, the cardiovascular, respiratory, genitourinary systems, digestive tract, and sensory organs depend on the state of the autonomic nervous system. It also affects the functionality of the musculoskeletal system, regulates metabolic processes, ensuring the relative constancy of the internal environment of the body and its viability. Irritation or inhibition of the functions of individual autonomic structures leads to autonomic
imbalance, which to one degree or another affects a person’s condition, his health, and the quality of his life. In this regard, it is only worth emphasizing the exceptional diversity of clinical manifestations caused by autonomic dysfunction, and drawing attention to the fact that representatives of almost all clinical disciplines are concerned about the problems arising in connection with this.
Next, we have the opportunity to dwell only on some clinical phenomena that depend on the state of the autonomic nervous system, with which a neurologist has to deal in everyday work (see also Chapters 22, 30, 31).
13.3.9. Acute autonomic dysfunction, manifested by extinction of autonomic reactions
Autonomic imbalance is usually accompanied by clinical manifestations, the nature of which depends on its characteristics. Acute autonomic dysfunction (pandysautonomia) due to inhibition of autonomic functions is caused by an acute violation of autonomic regulation, manifested totally, in all tissues and organs. During the period of this multisystem failure, which is usually associated with immune disorders in peripheral myelin fibers, immobility and areflexia of the pupils, dry mucous membranes, orthostatic hypotension occur, the heart rate slows down, intestinal motility is disrupted, and bladder hypotension occurs. Mental functions, the condition of muscles, including oculomotor muscles, coordination of movements, and sensitivity remain intact. There may be a change in the sugar curve according to the diabetic type, and an increase in protein content in the CSF. Acute autonomic dysfunction may gradually regress after some time, and in most cases recovery occurs.
13.3.10. Chronic autonomic dysfunction
Chronic autonomic dysfunction occurs during prolonged periods of bed rest or in conditions of weightlessness. It manifests itself mainly as dizziness and coordination disorders, which, upon returning to normal mode, gradually, over the course of several days, decrease. Violation of autonomic functions can be caused by an overdose of certain medications. Thus, an overdose of antihypertensive drugs leads to orthostatic hypotension; when using drugs that affect thermoregulation, changes in vasomotor reactions and sweating occur.
Some diseases can cause secondary autonomic disorders. Thus, diabetes mellitus and amyloidosis are characterized by manifestations of neuropathy, in which severe orthostatic hypotension, changes in pupillary reactions, impotence, and bladder dysfunction are possible. With tetanus, arterial hypertension, tachycardia, and hyperhidrosis occur.
13.3.11. Thermoregulation disorders
Thermoregulation can be represented as a cybernetic self-governing system, while the thermoregulatory center, which provides a set of physiological reactions of the body aimed at maintaining a relative constancy of body temperature, is located in the hypothalamus and adjacent areas of the diencephalon. Information flows to it from thermoreceptors located in various organs and tissues. The thermoregulation center, in turn, regulates the processes of heat production and heat transfer in the body through nerve connections, hormones and other biologically active substances. In case of thermoregulation disorder (in animal experiments, when the brain stem is transected), body temperature becomes excessively dependent on the ambient temperature (poikilothermia).
The state of body temperature is affected by changes in heat production and heat transfer due to various reasons. If body temperature rises to 39? C, patients usually experience malaise, drowsiness, weakness, headache and muscle pain. At temperatures above 41.1? C, children often experience seizures. If the temperature rises to 42.2°C or higher, irreversible changes in brain tissue may occur, apparently due to protein denaturation. Temperatures above 45.6? C are incompatible with life. When the temperature drops to 32.8 °C, consciousness is impaired, at 28.5 °C atrial fibrillation begins, and even greater hypothermia causes fibrillation of the ventricles of the heart.
When the function of the thermoregulatory center in the preoptic area of the hypothalamus is impaired (vascular disorders, more often hemorrhages, encephalitis, tumors), endogenous central hyperthermia. It is characterized by changes in daily fluctuations in body temperature, cessation of sweating, lack of response when taking antipyretic drugs, impaired thermoregulation, in particular the severity of a decrease in body temperature in response to its cooling.
In addition to hyperthermia caused by dysfunction of the thermoregulatory center, increased heat production may be associated with other reasons. She possible, in particular, with thyrotoxicosis (body temperature may be 0.5-1.1? C higher than normal), increased activation of the adrenal medulla, menstruation, menopause and other conditions accompanied by endocrine imbalance. Hyperthermia can also be caused by extreme physical exertion. For example, when running a marathon distance, body temperature sometimes rises to 39-41? C. Reason hyperthermia may also result in decreased heat transfer. Due to this hyperthermia is possible with congenital absence of sweat glands, ichthyosis, widespread skin burns, as well as taking medications that reduce sweating (M-anticholinergics, MAO inhibitors, phenothiazines, amphetamines, LSD, some hormones, especially progesterone, synthetic nucleotides).
Infectious agents are the most common exogenous cause of hyperthermia. (bacteria and their endotoxins, viruses, spirochetes, yeasts). It is believed that all exogenous pyrogens affect thermoregulatory structures through an intermediary substance - endogenous pyrogen (EP), identical to interleukin-1, which is produced by monocytes and macrophages.
Endogenous pyrogen in the hypothalamus stimulates the synthesis of prostaglandins E, which change the mechanisms of heat production and heat transfer by enhancing the synthesis of cyclic adenosine monophosphate. Endogenous pyrogen, contained in astrocytes of the brain, can be released during cerebral hemorrhage, traumatic brain injury, causing an increase in body temperature, this may activate neurons responsible for slow-wave sleep. The latter circumstance explains lethargy and drowsiness during hyperthermia, which can be considered as one of the protective reactions. For infectious processes or acute inflammation hyperthermia plays an important role in the development of immune responses, which can be protective, but sometimes also lead to an increase in pathological manifestations.
Permanent non-infectious hyperthermia (psychogenic fever, habitual hyperthermia) - permanent low-grade fever (37-38? C) for several weeks, less often - several months and even years. The temperature rises monotonously and does not have a circadian rhythm, is accompanied by a decrease or cessation of sweating, and lack of response to antipyretic drugs (amidopyrine, etc.), violation of adaptation to external cooling. Characteristic satisfactory tolerance of hyperthermia, maintaining ability to work. Permanent non-infectious hyperthermia most often occurs in children and young women during periods of emotional stress and usually regarded as one of the signs of autonomic dystonia syndrome. However, especially in older people, it can also be a consequence of organic damage to the hypothalamus (tumor, vascular disorders, especially hemorrhage, encephalitis). A variant of psychogenic fever can apparently be considered Hines-Bennick syndrome (described by Hines-Bannick M.), arising as a consequence of vegetative imbalance, manifested by general weakness (asthenia), permanent hyperthermia, severe hyperhidrosis, and goose bumps. May be triggered by mental trauma.
Temperature crises (paroxysmal non-infectious hyperthermia) - sudden increases in temperature to 39-41? C, accompanied by a chill-like state, a feeling of internal tension, facial hyperemia, tachycardia. The elevated temperature persists for several hours, after which a lytic decrease usually occurs, accompanied by general weakness and weakness, noted for several hours. Crises can occur against the background of normal body temperature or prolonged low-grade fever (permanent-paroxysmal hyperthermia). With them, changes in the blood, in particular its leukocyte formula, are uncharacteristic. Temperature crises are one of the possible manifestations of vegetative dystonia and dysfunction of the thermoregulatory center, part of the hypothalamic structures.
Malignant hyperthermia - a group of hereditary conditions characterized by a sharp increase in body temperature to 39-42? C in response to the administration of inhalation anesthetics, as well as muscle relaxants, especially ditilin, at the same time there is insufficient muscle relaxation, the appearance of fasciculations in response to the administration of dithiline. The tone of the masticatory muscles often increases, difficulties are created for intubation, which may be a reason to increase the dose of a muscle relaxant and (or) anesthetic, leads to the development of tachycardia and in 75% of cases to generalized muscle stiffness (rigid form of reaction). Against this background, it can be noted high activity
creatine phosphokinase (CPK) And myoglobinuria, severe respiratory and metabolic symptoms develop acidosis and hyperkalemia, may occur ventricular fibrillation, decreased blood pressure, appears marble cyanosis, arises threat of death.
The risk of developing malignant hyperthermia during inhalation anesthesia is especially high in patients suffering from Duchenne myopathy, central core myopathy, Thomsen's myotonia, chondrodystrophic myotonia (Schwartz-Jampel syndrome). It is assumed that malignant hyperthermia is associated with the accumulation of calcium in the sarcoplasm of muscle fibers. Tendency to malignant hyperthermia inherited in most cases in an autosomal dominant manner with different penetrance of the pathological gene. There is also malignant hyperthermia, inherited according to the recessive type (King's syndrome).
Laboratory tests in cases of malignant hyperthermia reveal signs of respiratory and metabolic acidosis, hyperkalemia and hypermagnesemia, increased levels of lactate and pyruvate in the blood. Late complications of malignant hyperthermia include massive swelling of skeletal muscles, pulmonary edema, disseminated intravascular coagulation, and acute renal failure.
Neuroleptic malignant hyperthermia along with high body temperature, it is manifested by tachycardia, arrhythmia, blood pressure instability, sweating, cyanosis, tachypnea, while water-electrolyte imbalance occurs with an increase in the concentration of potassium in the plasma, acidosis, myoglobinemia, myoglobinuria, increased activity of CPK, AST, ALT, signs of DIC syndrome appear. Muscle contractures appear and increase, and a coma develops. Pneumonia and oliguria are added. In pathogenesis, the role of impaired thermoregulation and disinhibition of the dopamine system in the tubero-infundibular region of the hypothalamus is important. Death occurs most often after 5-8 days. An autopsy reveals acute dystrophic changes in the brain and parenchymal organs. Syndrome develops as a result of long-term treatment with neuroleptics, however, it can develop in patients with schizophrenia who have not taken antipsychotics, and rarely in patients with parkinsonism who have been taking L-DOPA drugs for a long time.
Chill Syndrome - an almost constant feeling of chilliness in the whole body or in its individual parts: in the head, back, etc., usually combined with senestopathies and manifestations of hypochondriacal syndrome, sometimes with phobias. Patients are afraid of cold weather, drafts, and usually wear excessively warm clothes. Their body temperature is normal; in some cases, permanent hyperthermia is detected. Viewed as one of the manifestations of autonomic dystonia with a predominance of activity of the parasympathetic division of the autonomic nervous system.
For the treatment of patients with non-infectious hyperthermia, it is advisable to use beta or alpha-blockers (phentolamine 25 mg 2-3 times a day, pyrroxan 15 mg 3 times a day), general restorative treatment. For persistent bradycardia and spastic dyskinesia, belladonna preparations (bellataminal, belloid, etc.) are prescribed. The patient should give up smoking and alcohol abuse.
13.3.12. Tearing disorders
The secretory function of the lacrimal glands is ensured mainly by the influence on them of impulses coming from the parasympathetic lacrimal nucleus, located in the pons near the nucleus of the facial nerve and receiving stimulating impulses from the structures of the limbic-reticular complex. From the parasympathetic lacrimal nucleus, impulses travel along the intermediate nerve and its branch - the greater petrosal nerve - to the parasympathetic pterygopalatine ganglion. The axons of the cells located in this ganglion make up the lacrimal nerve, which innervates the secretory cells of the lacrimal gland. Sympathetic impulses pass to the lacrimal gland from the cervical sympathetic ganglia along the fibers of the carotid plexus and cause mainly vasoconstriction in the lacrimal glands. During the day, the human lacrimal gland produces approximately 1.2 ml of tear fluid. Tear production occurs mainly during periods of wakefulness and is suppressed during sleep.
Impaired tear production can be in the form of dry eyes due to insufficient production of tear fluid by the lacrimal glands. Excessive lacrimation (epiphora) is often associated with a violation of the outflow of tears into the nasal cavity through the nasolacrimal duct.
Dryness (xerophthalmia, alacrimia) eyes may be a consequence of damage to the lacrimal glands themselves or a disorder of their parasympathetic innervation. Impaired secretion of tear fluid - one of the characteristic signs of Sjögren's dry mucous membrane syndrome (H.S. Sjogren), congenital Riley-Day dysautonomia, acute transient total dysautonomia, Mikulicz syndrome. Unilateral xerophthalmia is more common when the facial nerve is damaged proximal to the origin of its branch - the greater petrosal nerve. A typical picture of xerophthalmia, often complicated by inflammation of the tissues of the eyeball, is sometimes observed in patients operated on for neuroma of the VIII cranial nerve, during which the fibers of the facial nerve deformed by the tumor were cut.
Prosoplegia due to neuropathy of the facial nerve, in which this nerve is damaged below the origin of the greater petrosal nerve, usually occurs lacrimation, resulting from paresis of the orbicularis oculi muscle, the lower eyelid and, in connection with this, a violation of the natural outflow of tear fluid through the nasolacrimal canal. The same reason underlies senile lacrimation, associated with a decrease in the tone of the orbicularis oculi muscle, as well as vasomotor rhinitis, conjunctivitis, leading to swelling of the wall of the nasolacrimal canal. Paroxysmal excessive lacrimation due to swelling of the walls of the nasolacrimal duct during a painful attack occurs during cluster pain and attacks of vegetative prosopalgia. Lacrimation may be a reflex, triggered by irritation of the innervation zone of the first branch of the trigeminal nerve. with cold epiphora (tearing in the cold) vitamin A deficiency, severe exophthalmos. Increased tearing while eating characteristic of the “crocodile tears” syndrome, described in 1928 by F.A. Bogarde. This syndrome can be congenital or occurs in the recovery stage of facial neuropathy. In parkinsonism, lacrimation may be one of the manifestations of the general activation of cholinergic mechanisms, as well as a consequence of hypomimia and rare blinking, which weakens the ability of the outflow of tear fluid through the nasolacrimal duct.
Treatment of patients with lacrimation disorders depends on the causes that cause them. With xerophthalmia, it is necessary to monitor the condition of the eye and take measures aimed at maintaining its moisture and preventing infection, instilling oil solutions, albucide, etc. into the eyes. Recently they began to use artificial tear fluid.
13.3.13. Salivation disorders
Dry mouth (hyposalivation, xerostomia) And excessive salivation (hypersalivation, sialorrhea) may be due to various reasons. Hypo- and hypersalivation can be permanent or paroxysmal,
at night, the production of saliva is less; when eating and even at the sight of food and its smell, the amount of saliva secreted increases. Typically, from 0.5 to 2 liters of saliva are produced per day. Under the influence of parasympathetic impulses, the salivary glands produce abundant liquid saliva, while activation of sympathetic innervation leads to the production of thicker saliva.
Hypersalivationcommon in parkinsonism, bulbar and pseudobulbar syndrome, cerebral palsy; in these pathological conditions it may be caused by both hyperproduction of saliva and disturbances in the act of swallowing, the latter circumstance usually leads to spontaneous flow of saliva from the mouth even in cases of its secretion in normal quantities. Hypersalivation can be a consequence of ulcerative stomatitis, helminthic infestation, toxicosis of pregnant women, in some cases it is considered psychogenic.
Cause of persistent hyposalivation (xerostomia) is Sjögren's syndrome(dry syndrome), in which xerophthalmia (dry eyes), dry conjunctiva, nasal mucosa, dysfunction of other mucous membranes, and swelling in the area of the parotid salivary glands simultaneously occur. Hyposalivation is a sign of glossodynia, stomalgia, total dysautonomia, she can occur with diabetes mellitus, diseases of the gastrointestinal tract, fasting, under the influence of certain medications (nitrazepam, lithium preparations, anticholinergics, antidepressants, antihistamines, diuretics, etc.), during radiation therapy. Dry mouth usually occurs when excited due to the predominance of sympathetic reactions, it is possible in a depressed state.
If salivation is impaired, it is desirable to clarify its cause and then carry out possible pathogenetic therapy. Anticholinergics can be used as a symptomatic remedy for hypersalivation; for xerostomia - bromhexine (1 tablet 3-4 times a day), pilocarpine (capsules 5 mg sublingually 1 time a day), nicotinic acid, vitamin A preparations. As a replacement treatment artificial saliva is used.
13.3.14. Sweating disorders
Sweating is one of the factors influencing thermoregulation, and is in certain dependence on the state of the thermoregulatory center, which is part of the hypothalamus and exerts global
influence on the sweat glands, which, based on the morphological features, location and chemical composition of the sweat they secrete, are differentiated into merocrine and apocrine, while the role of the latter in the occurrence of hyperhidrosis is insignificant.
Thus, the thermoregulation system consists mainly of certain structures of the hypothalamus (preoptic zone of the hypothalamic region) (Guyton A., 1981), their connections with the integumentary and merocrine sweat glands located in the skin. The hypothalamic part of the brain, through the autonomic nervous system, provides regulation of heat transfer, controlling the state of skin vascular tone and the secretion of sweat glands,
Moreover, most sweat glands have sympathetic innervation, but the mediator of the postganglionic sympathetic fibers approaching them is acetylcholine. There are no adrenergic receptors in the postsynaptic membrane of the merocrine sweat glands, but some cholinergic receptors can also respond to adrenaline and norepinephrine circulating in the blood. It is generally accepted that only the sweat glands of the palms and soles have dual cholinergic and adrenergic innervation. This explains their increased sweating during emotional stress.
Increased sweating may be a normal reaction to external stimuli (thermal exposure, physical activity, excitement). At the same time, excessive, stable, localized or generalized hyperhidrosis can be a consequence of some organic neurological, endocrine, oncological, general somatic, and infectious diseases. In cases of pathological hyperhidrosis, the pathophysiological mechanisms are different and are determined by the characteristics of the underlying disease.
Local pathological hyperhidrosis observed relatively rarely. In most cases this is the so-called idiopathic hyperhidrosis, in which excessive sweating is observed mainly on the palms, soles, and armpits. It appears from 15-30 years of age, more often in women. Over time, excessive sweating may gradually stop or become chronic. This form of local hyperhidrosis is usually combined with other signs of vegetative lability, and is often observed in the patient’s relatives.
Local hyperhidrosis is also associated with ingestion of food or hot drinks, especially coffee and spicy foods. Sweat appears primarily on the forehead and upper lip. The mechanism of this form of hyperhidrosis has not been clarified. The cause of local hyperhidrosis in one of the forms is more definite vegetative prosopalgia - Baillarger-Frey syndrome, described in French mi doctors - in 1847 J. Baillarger (1809-1890) and in 1923 L. Frey (auriculotemporal syndrome), resulting from damage to the auriculotemporal nerve due to inflammation of the parotid salivary gland. Mandatory pro- the phenomenon of an attack in this disease is skin hyperemia and increased sweating in the parotid-temporal region. The occurrence of attacks is usually provoked by eating hot food, general overheating, smoking, physical work, and emotional stress. Bailhardt-Frey syndrome can also occur in newborns whose facial nerve was damaged during forceps delivery.
Cord tympani syndrome characterized by increased sweating in the chin area, usually in response to a taste sensation. It occurs after operations on the submandibular gland.
Generalized hyperhidrosis occurs much more often than local. Physiological its mechanisms are different. Here are some of the conditions that cause hyperhidrosis.
1. Thermoregulatory sweating, which occurs throughout the body in response to increased ambient temperature.
2. Generalized excessive sweating can be a consequence of psychogenic stress, a manifestation of anger and especially fear; hyperhidrosis is one of the objective manifestations of intense pain felt by the patient. However, during emotional reactions, sweating can occur in limited areas: face, palms, feet, armpits.
3. Infectious diseases and inflammatory processes in which pyrogenic substances appear in the blood, which leads to the formation of a triad: hyperthermia, chills, hyperhidrosis. The nuances of development and course characteristics of the components of this triad often depend on the characteristics of the infection and the state of the immune system.
4. Changes in the level of metabolism in certain endocrine disorders: acromegaly, thyrotoxicosis, diabetes mellitus, hypoglycemia, menopausal syndrome, pheochromocytoma, hyperthermia of various origins.
5. Oncological diseases (primarily cancer, lymphoma, Hodgkin's disease), in which products of metabolism and tumor decay enter the blood, giving a pyrogenic effect.
Pathological changes in sweating are possible with brain lesions accompanied by dysfunction of its hypothalamic region. Sweating disorders can be provoked by acute cerebrovascular accidents, encephalitis, and space-occupying pathological processes in the cranial cavity. In Parkinsonism, hyperhidrosis on the face is often observed. Hyperhidrosis of central origin is characteristic of familial dysautonomia (Riley-Day syndrome).
The state of sweating is influenced by many medications (aspirin, insulin, some analgesics, cholinomimetics and anticholinesterase drugs - prozerin, calemin, etc.). Hyperhidrosis can be triggered by alcohol, drugs, and can be one of the manifestations of withdrawal symptoms or withdrawal reactions. Pathological sweating is one of the manifestations of poisoning with organophosphorus substances (OPS).
Occupies a special place essential form of hyperhidrosis, in which the morphology of the sweat glands and the composition of sweat are not changed. The etiology of this condition is unknown; pharmacological blockade of sweat gland activity does not bring sufficient success.
When treating patients with hyperhidrosis, M-anticholinergics (cyclodol, akineton, etc.), small doses of clonidine, Sonapax, and beta-blockers may be recommended. Topically applied astringents are more effective: solutions of potassium permanganate, aluminum salts, formalin, tannic acid.
Anhidrosis(no sweating) may be a consequence of sympathectomy. Spinal cord injury is usually accompanied by anhidrosis on the trunk and extremities below the lesion. With complete Horner's syndrome Along with the main signs (miosis, pseudoptosis, endophthalmos) on the face on the affected side, skin hyperemia, dilatation of conjunctival vessels and anhidrosis can usually be noted. Anhidrosis may be detected in the area innervated by damaged peripheral nerves. Anhidrosis on the trunk
and lower extremities there may be a consequence of diabetes mellitus, in such cases, patients do not tolerate heat well. They may experience increased sweating on the face, head, and neck.
13.3.15. Alopecia
Neurotic alopecia (Michelson's alopecia) - baldness that occurs as a result of neurotrophic disorders in diseases of the brain, primarily the structures of the diencephalic part of the brain. Treatment for this form of the neurotrophic process has not been developed. Alopecia can be a consequence of x-ray or radioactive radiation.
13.3.16. Nausea and vomiting
Nausea(nausea)- a peculiar painful sensation in the throat, in the epigastric region of an impending urge to vomit, signs of incipient antiperistalsis. It occurs due to excitation of the parasympathetic part of the autonomic nervous system, for example, due to excessive irritation of the vestibular apparatus or the vagus nerve. Accompanied by pallor, hyperhidrosis, profuse salivation, and often bradycardia and arterial hypotension.
Vomit(vomitus, emesis)- a complex reflex act, manifested by involuntary ejection, eruption of the contents of the digestive tract (mainly the stomach) through the mouth, less often through the nose. It may be caused by direct irritation of the vomiting center - the chemoreceptor zone located in the tegmentum of the medulla oblongata (cerebral vomiting). Such an irritating factor can be a focal pathological process (tumor, cysticercosis, hemorrhage, etc.), as well as hypoxia, the toxic effects of anesthetics, opiates, etc.). Brain vomiting occurs more often due to increased intracranial pressure, it often appears in the morning on an empty stomach, usually without warning and has a gushing character. The cause of cerebral vomiting can be encephalitis, meningitis, brain injury, brain tumor, acute cerebrovascular accident, cerebral edema, hydrocephalus (all its forms except vicarious or replacement).
Psychogenic vomiting - possible manifestation of a neurotic reaction, neurosis, mental disorders.
Often The cause of vomiting is various factors that secondary irritate the receptors of the vagus nerve at different levels: in the diaphragm, organs of the digestive tract. In the latter case, the afferent part of the reflex arc consists mainly of the main, sensitive portion of the vagus nerve, and the efferent part consists of the motor portions of the trigeminal, glossopharyngeal and vagus nerves. Vomiting may also occur a consequence of overexcitation of the vestibular apparatus (seasickness, Meniere's disease, etc.).
The act of vomiting consists of successive contractions of various muscle groups (diaphragm, abdominals, pylorus, etc.), while the epiglottis descends, the larynx and soft palate rise, which leads to isolation (not always sufficient) of the respiratory tract from vomiting.
wt. Vomiting may be a protective reaction of the digestive system to the entry or formation of toxic substances in it. In severe general condition of the patient, vomiting can cause aspiration of the respiratory tract; repeated vomiting is one of the causes of dehydration.
13.3.17. Hiccups
Hiccups(singultus)- involuntary myoclonic contraction of the respiratory muscles, simulating a fixed inhalation, while suddenly the airways and the air flow passing through them are blocked by the epiglottis and a characteristic sound occurs. In healthy people, hiccups can be a consequence of irritation of the diaphragm caused by overeating or drinking cold drinks. In such cases, the hiccups are isolated and short-lived. Persistent hiccups may be a consequence of irritation of the lower parts of the brain stem due to cerebrovascular accidents, a subtentorial tumor or traumatic injury to the brain stem, increasing intracranial hypertension and in such cases is a sign signaling a threat to the patient’s life. Irritation of the spinal nerve C IV, as well as the phrenic nerve by a tumor of the thyroid gland, esophagus, mediastinum, lungs, arteriovenous malformation, lymphoma of the neck, etc., can also be dangerous. Gastrointestinal diseases, pancreatitis, subphrenic abscess, and intoxication can also cause hiccups alcohol, barbiturates, narcotic drugs. Repeated hiccups are also possible as one of the manifestations of a neurotic reaction.
13.3.18. Disorders of the innervation of the cardiovascular system
Disorders of the innervation of the heart muscle affect the state of general hemodynamics. The absence of sympathetic influences on the heart muscle limits the increase in stroke volume of the heart, and the insufficiency of the influences of the vagus nerve leads to the appearance of tachycardia at rest, while various types of arrhythmia, lipothymia, and syncope are possible. Disruption of the innervation of the heart in patients with diabetes mellitus leads to similar phenomena. General autonomic disorders may be accompanied by attacks of orthostatic blood pressure drop that occur during sudden movements when the patient tries to quickly assume a vertical position. Vegetative-vascular dystonia can also be manifested by pulse lability, changes in the rhythm of cardiac activity, and a tendency to angiospastic reactions, in particular to vascular headaches, a variant of which are various forms of migraine.
In patients with orthostatic hypotension, a sharp decrease in blood pressure is possible under the influence of many medications: antihypertensives, tricyclic antidepressants, phenothiazines, vasodilators, diuretics, insulin. The denervated human heart functions in accordance with the Frank-Starling rule: the force of contraction of myocardial fibers is proportional to the initial value of their stretch.
13.3.19. Disturbance of the sympathetic innervation of the smooth muscles of the eye (Bernard-Horner syndrome)
Bernard-Horner syndrome, or Horner's syndrome. Sympathetic innervation of the smooth muscles of the eye and its appendages is provided by nerve impulses coming from the nuclear structures of the posterior part of the hypothalamic part of the brain, which along descending pathways pass through the trunk and cervical spinal cord and end in Jacobson cells, which form in the lateral horns of the C VIII-D I segments spinal cord Budge-Weller ciliospinal center. From it, along the axons of Jacobson cells passing through the corresponding anterior roots, spinal nerves and white communicating branches, they enter the cervical section of the paravertebral sympathetic chain, reaching the superior cervical sympathetic ganglion. Next, the impulses continue their journey along postganglionic fibers, which take part in the formation of the sympathetic plexus of the common and internal carotid arteries, and reach the cavernous sinus. From here they, together with the ophthalmic artery, penetrate the orbit and innervate the following smooth muscles: dilator pupillary muscle, orbital muscle and cartilage muscle of the upper eyelid (m. dilatator pupillae, m. orbitalis And m. tarsalis superior).
Disruption of the innervation of these muscles, which occurs when any part of the path of sympathetic impulses coming to them from the posterior part of the hypothalamus is damaged, leads to their paresis or paralysis. In this regard, on the side of the pathological process, Horner's syndrome or Claude Bernard-Horner, manifesting constriction of the pupil (paralytic miosis), slight enophthalmos and so-called pseudoptosis (lowering of the upper eyelid), causing some narrowing of the palpebral fissure (Fig. 13.3). Due to the preservation of the parasympathetic innervation of the sphincter of the pupil on the side of Horner's syndrome, the pupil's reaction to light remains intact.
Due to disruption of vasoconstrictor reactions on the homolateral half of the face Horner's syndrome is usually accompanied by hyperemia of the conjunctiva and skin; heterochromia of the iris and impaired sweating are also possible. Changes in sweating on the face can help clarify the topic of damage to sympathetic structures in Horner's syndrome. With postganglionic localization of the process, impaired sweating on the face is limited to one side of the nose and the paramedian area of the forehead. If sweating is disturbed on the entire half of the face, the damage to the sympathetic structures is preganglionic.
Since ptosis of the upper eyelid and constriction of the pupil can have different origins, in order to make sure that in this case there are manifestations of Horner's syndrome, you can check the reaction of the pupils to instillation of an M-anticholinergic solution into both eyes. After this, with Horner's syndrome, pronounced anisocoria will appear, since on the side of the manifestations of this syndrome, pupil dilation will be absent or will appear slightly.
Thus, Horner's syndrome indicates a violation of the sympathetic innervation of the smooth muscles of the eye and the corresponding half of the face. It may be a consequence of damage to the nuclei of the posterior part of the hypothalamus, the central sympathetic pathway at the level of the brain stem or cervical spinal cord, the ciliospinal center, preganglionic fibers extending from it,
Rice. 13.3.Sympathetic innervation of the eye.
a - diagram of pathways: 1 - vegetative cells of the hypothalamus; 2 - ophthalmic artery; 3 - internal carotid artery; 4, 5 - middle and upper nodes of the paravertebral sympathetic chain; 6 - star knot; 7 - body of the sympathetic neuron in the ciliospinal center of the spinal cord; b - appearance of the patient with a violation of the sympathetic innervation of the left eye (Bernard-Horner syndrome).
the superior cervical ganglion and the postganglionic sympathetic fibers coming from it, forming the sympathetic plexus of the external carotid artery and its branches. Horner's syndrome can be caused by lesions of the hypothalamus, brain stem, cervical spinal cord, sympathetic structures in the neck, plexus of the external carotid artery and its branches. Such lesions can be caused by trauma to these structures of the central nervous system and peripheral nervous system, a volumetric pathological process, cerebrovascular diseases, and sometimes demyelination in multiple sclerosis. An oncological process accompanied by the development of Horner's syndrome may be cancer of the upper lobe of the lung, growing into the pleura (Pancoast cancer).
13.3.20. Innervation of the bladder and its disorders
Of great practical importance is the identification of dysfunctions of the bladder, which arise in connection with a disorder of its innervation, which is provided mainly by the autonomic nervous system (Fig. 13.4).
Afferent somatosensory fibers originate from the proprioceptors of the bladder, which respond to its stretching. The nerve impulses arising in these receptors penetrate through the spinal nerves S II - S IV
Rice. 13.4.Innervation of the bladder [according to Müller].
1 - paracentral lobule; 2 - hypothalamus; 3 - upper lumbar spinal cord; 4 - lower sacral spinal cord; 5 - bladder; 6 - genital nerve; 7 - hypogastric nerve; 8 - pelvic nerve; 9 - plexus of the bladder; 10 - bladder detrusor; 11 - internal sphincter of the bladder; 12 - external sphincter of the bladder.
into the posterior cords of the spinal cord, then enter the reticular formation of the brain stem and further - into the paracentral lobules of the cerebral hemispheres, Moreover, along the way, part of these impulses passes to the opposite side.
Thanks to the information going through the indicated peripheral, spinal and cerebral structures to the paracentral lobules, the stretching of the bladder when it is filled is realized, and the presence of incomplete over-
The cross of these afferent pathways leads to the fact that with the cortical localization of the pathological focus, a violation of the control of pelvic functions usually occurs only when both paracentral lobules are affected (for example, with falx meningioma).
Efferent innervation of the bladder is carried out mainly due to the paracentral lobules, the reticular formation of the brain stem and spinal autonomic centers: sympathetic (neurons of the lateral horns of segments Th XI - L II) and parasympathetic, located at the level of spinal cord segments S II - S IV. Conscious regulation of urination is carried out mainly due to nerve impulses coming from the motor zone of the cerebral cortex and the reticular formation of the trunk to the motor neurons of the anterior horns of segments S III - S IV. It is clear that to ensure nervous regulation of the bladder, it is necessary to preserve the pathways connecting these structures of the brain and spinal cord with each other, as well as the formations of the peripheral nervous system that provide innervation to the bladder.
Preganglionic fibers coming from the lumbar sympathetic center of the pelvic organs (L 1 -L 2) pass as part of the presacral and hypogastric nerves, in transit through the caudal sections of the sympathetic paravertebral trunks and along the lumbar splanchnic nerves (nn. splanchnici lumbales) they reach the nodes of the inferior mesenteric plexus (plexus mesentericus inferior). Postganglionic fibers coming from these nodes take part in the formation of the nerve plexuses of the bladder and provide innervation primarily to its internal sphincter. Due to sympathetic stimulation of the bladder, the internal sphincter formed by smooth muscles contracts; in this case, as the bladder fills, the muscle of its wall stretches - the muscle that pushes urine out (m. detrusor vesicae). All this ensures urine retention, which is facilitated by the simultaneous contraction of the external striated sphincter of the bladder, which has somatic innervation. Her carried out by the pudendal nerves (nn. pudendi), consisting of axons of motor neurons located in the anterior horns of the S III S IV segments of the spinal cord. Efferent impulses to the pelvic floor muscles and counter proprioceptive afferent signals from these muscles also pass through the pudendal nerves.
Parasympathetic innervation of the pelvic organs carried out by preganglionic fibers coming from the parasympathetic center of the bladder, located in the sacral part of the spinal cord (S I -S III). They participate in the formation of the pelvic plexus and reach the intramural (located in the wall of the bladder) ganglia. Parasympathetic stimulation causes contraction of the smooth muscle that forms the body of the bladder (m. detrusor vesicae) and a concomitant relaxation of its smooth sphincters, as well as increased intestinal motility, which creates conditions for emptying the bladder. Involuntary spontaneous or provoked contraction of the bladder detrusor (detrusor overactivity) leads to urinary incontinence. Detrusor overactivity can be neurogenic (for example, in multiple sclerosis) or idiopathic (in the absence of an identified cause).
Urinary retention (retentio urinae) more often occurs as a result of damage to the spinal cord above the location of the spinal sympathetic autonomic centers (Th XI -L II), responsible for the innervation of the bladder.
Urinary retention is caused by dyssynergia of the detrusor and bladder sphincters (contraction of the internal sphincter and relaxation of the detrusor). So
happens, for example, with traumatic damage to the spinal cord, intravertebral tumor, multiple sclerosis. In such cases, the bladder becomes full and its bottom can rise to the level of the navel and above. Urinary retention is also possible due to damage to the parasympathetic reflex arc, which closes in the sacral segments of the spinal cord and provides innervation to the detrusor of the bladder. The cause of paresis or detrusor paralysis can be either a lesion at this level of the spinal cord or a disorder in the function of the structures of the peripheral nervous system that make up the reflex arc. In cases of persistent urinary retention, patients usually need to empty the bladder through a catheter. Along with urinary retention, neuropathic fecal retention usually occurs. (retencia alvi).
Partial damage to the spinal cord above the level of the autonomic spinal centers responsible for the innervation of the bladder can lead to disruption of voluntary control of urination and the occurrence of so-called imperative urge to urinate, in which the patient, feeling the urge, is unable to hold urine. A major role is likely to be a disturbance in the innervation of the external sphincter of the bladder, which normally can be controlled to a certain extent by willpower. Such manifestations of bladder dysfunction are possible, in particular with bilateral damage to the medial structures of the lateral cords in patients with an intramedullary tumor or multiple sclerosis.
A pathological process that affects the spinal cord at the level of the location of the sympathetic autonomic centers of the bladder (cells of the lateral horns of Th I -L II segments of the spinal cord) leads to paralysis of the internal sphincter of the bladder, while the tone of its protrusor is increased, in connection with this there is a constant release of urine in drops - true urinary incontinence (incontinentia urinae vera) As it is produced by the kidneys, the bladder is practically empty. True urinary incontinence may be caused by spinal stroke, spinal cord injury, or spinal tumor at the level of these lumbar segments. True urinary incontinence may also be associated with damage to the structures of the peripheral nervous system involved in the innervation of the bladder, in particular with diabetes mellitus or primary amyloidosis.
When urine retention occurs due to damage to the structures of the central or peripheral nervous system, it accumulates in the overstretched bladder and can create such high pressure in it that, under its influence, the internal and external sphincters of the bladder, which are in a state of spastic contraction, are stretched. In this regard, urine is constantly released through the urethra in drops or periodically in small portions while the bladder remains full - paradoxical urinary incontinence (incontinentia urinae paradoxa), which can be established by identifying by visual examination, as well as by palpation and percussion of the lower abdomen, the protrusion of the bottom of the bladder above the pubis (sometimes to the navel).
With damage to the parasympathetic spinal center (segments of the spinal cord S I -S III) and the corresponding roots of the cauda equina, weakness may develop and simultaneous impairment of the sensitivity of the muscle that pushes urine (m. detrusor vesicae), this causes urinary retention.
However, in such cases, over time, it is possible to restore reflex emptying of the bladder; it begins to function in an “autonomous” mode (autonomous bladder).
Clarifying the nature of bladder dysfunction can help determine the topical and nosological diagnoses of the underlying disease. In order to clarify the characteristics of bladder function disorders, along with a thorough neurological examination, if indicated, radiography of the upper urinary tract, bladder and urethra is performed using radiopaque solutions. The results of urological examinations, in particular cystoscopy and cystometry (determining the pressure in the bladder during filling with liquid or gas), can help clarify the diagnosis. In some cases, electromyography of the periurethral striated muscles may be informative.
Autonomic nervous system
Some general principles of organization of sensory and motor systems will be very useful to us when studying systems of internal regulation. All three divisions of the autonomic nervous system have “sensory” and “motor” components. While the former record indicators of the internal environment, the latter enhance or inhibit the activity of those structures that carry out the regulation process itself.
Intramuscular receptors, along with receptors located in tendons and some other places, respond to pressure and stretch. Together they make up a special kind of internal sensory system that helps control our movements.
Receptors involved in homeostasis operate in a different way: they sense changes in blood chemistry or pressure fluctuations in the vascular system and in hollow internal organs such as the digestive tract and bladder. These sensory systems, which collect information about the internal environment, are very similar in organization to systems that perceive signals from the surface of the body. Their receptor neurons form the first synaptic switches within the spinal cord. Along the motor pathways of the autonomic system, commands go to the organs that directly regulate the internal environment. These pathways begin with special autonomic preganglionic neurons in the spinal cord. This organization is somewhat reminiscent of the organization of the spinal level of the motor system.
The main focus of this chapter will be on those motor components of the autonomic system that innervate the muscles of the heart, blood vessels and intestines, causing their contraction or relaxation. The same fibers innervate the glands, causing the process of secretion.
The autonomic nervous system consists of two large sections - sympathetic And parasympathetic. Both divisions share a structural feature that we have not encountered before: the neurons that control the muscles of the internal organs and glands lie outside the central nervous system, forming small encapsulated clusters of cells called ganglia. Thus, in the autonomic nervous system there is an additional link between the spinal cord and the end working organ (effector).
Autonomic neurons in the spinal cord integrate sensory information from internal organs and other sources. On this basis, they then regulate the activity of autonomic ganglion neurons. The connections between the ganglia and the spinal cord are called preganglionic fibers. The neurotransmitter used to transmit impulses from the spinal cord to ganglion neurons in both the sympathetic and parasympathetic divisions is almost always acetylcholine, the same transmitter that the spinal cord motor neurons directly control skeletal muscles. As in the fibers innervating skeletal muscles, the action of acetylcholine can be enhanced in the presence of nicotine and blocked by curare. Axons coming from neurons of the autonomic ganglia, or postganglionic fibers, then go to the target organs, forming many branches there.
Rice. 63.The sympathetic and parasympathetic divisions of the autonomic nervous system, the organs they innervate, and their effects on each organ.
The sympathetic and parasympathetic divisions of the autonomic nervous system differ from each other 1) in the levels at which preganglionic fibers exit the spinal cord; 2) according to the proximity of the ganglia to the target organs; 3) by neurotransmitter, which is used by postganglionic neurons to regulate the functions of these target organs. We will now consider these features.
Sympathetic nervous system
In the sympathetic system, preganglionic fibers emerge from breast And lumbar parts of the spinal cord. Its ganglia are located quite close to the spinal cord, and very long postganglionic fibers extend from them to the target organs (see Fig. 63). The main transmitter of the sympathetic nerves is norepinephrine, one of the catecholamines, which also serves as a mediator in the central nervous system.
To understand what organs the sympathetic nervous system affects, it is easiest to imagine what happens to an excited animal ready for a fight-or-flight response. The pupils dilate to let in more light; The heart rate increases and each contraction becomes more powerful, which leads to increased overall blood flow. Blood flows from the skin and internal organs to the muscles and brain. The motility of the gastrointestinal system weakens, digestion processes slow down. The muscles along the airways leading to the lungs relax, allowing the breathing rate to increase and gas exchange to increase. Liver and fat cells release more glucose and fatty acids, high-energy fuels, into the blood, and the pancreas is instructed to produce less insulin. This allows the brain to receive a larger share of the glucose circulating in the bloodstream, since, unlike other organs, the brain does not require insulin to utilize blood sugar. The mediator of the sympathetic nervous system, which carries out all these changes, is norepinephrine.
There is an additional system that has an even more generalized effect to more accurately ensure all these changes. The adrenal glands sit on the tops of the kidneys, like two small caps. In their inner part - the medulla - there are special cells innervated by preganglionic sympathetic fibers. During embryonic development, these cells are formed from the same neural crest cells from which the sympathetic ganglia are formed. Thus, the medulla is a component of the sympathetic nervous system. When activated by preganglionic fibers, medullary cells release their own catecholamines (norepinephrine and epinephrine) directly into the blood for delivery to target organs (Fig. 64). Circulating hormone mediators serve as an example of how regulation is carried out by endocrine organs (see p. 89).
Rice. 64.When sympathetic nerve activity causes the adrenal medulla to release catecholamines, these signaling substances are carried into the blood and influence the activity of various target tissues; thus, they ensure a coordinated response from organs that are distant from each other.
Parasympathetic nervous system
In the parasympathetic division, preganglionic fibers come from brain stem(“cranial component”) and from the lower, sacral segments of the spinal cord (see Fig. 63 above). They form, in particular, a very important nerve trunk called vagus nerve, whose numerous branches carry out all the parasympathetic innervation of the heart, lungs and intestinal tract. (The vagus nerve also relays sensory information from these organs back to the central nervous system.) Preganglionic parasympathetic axons are very long because their ganglia are typically located near or within the tissues they innervate.
A transmitter is used at the endings of the fibers of the parasympathetic system acetylcholine. The response of the corresponding target cells to acetylcholine is insensitive to the effects of nicotine or curare. Instead, acetylcholine receptors are activated by muscarine and blocked by atropine.
The predominance of parasympathetic activity creates conditions for “rest and restoration” of the body. In its extreme manifestation, the general pattern of parasympathetic activation resembles the state of rest that occurs after a satisfying meal. Increased blood flow to the digestive tract speeds up the movement of food through the intestines and increases the secretion of digestive enzymes. The frequency and strength of heart contractions decrease, the pupils narrow, the lumen of the airways decreases, and the formation of mucus in them increases. The bladder contracts. Taken together, these changes return the body to the peaceful state that preceded the fight-or-flight response. (All this is presented in Fig. 63; see also Chapter 6.)
Comparative characteristics of the parts of the autonomic nervous system
The sympathetic system, with its extremely long postganglionic fibers, is very different from the parasympathetic system, in which, on the contrary, the preganglionic fibers are longer and the ganglia are located near or inside the target organs. Many internal organs, such as the lungs, heart, salivary glands, bladder, gonads, receive innervation from both parts of the autonomic system (they have, as they say, “double innervation”). Other tissues and organs, such as muscle arteries, receive only sympathetic innervation. In general, we can say that the two departments work alternately: depending on the activity of the body and on the commands of the higher vegetative centers, first one or the other dominates.
This characterization, however, is not entirely correct. Both systems are constantly in a state of varying degrees of activity. The fact that target organs such as the heart or the iris can respond to impulses from both parts simply reflects their complementary roles. For example, when you are very angry, your blood pressure rises, which excites the corresponding receptors located in the carotid arteries. These signals are received by the integrating center of the cardiovascular system, located in the lower part of the brain stem and known as nuclei of the solitary tract. Excitation of this center activates the preganglionic parasympathetic fibers of the vagus nerve, which leads to a decrease in the frequency and strength of heart contractions. At the same time, under the influence of the same coordinating vascular center, sympathetic activity is suppressed, counteracting the increase in blood pressure.
How important is the functioning of each department for adaptive reactions? Surprisingly, not only animals, but also people can tolerate almost complete shutdown of the sympathetic nervous system without visible bad consequences. This switch-off is recommended for some forms of persistent hypertension.
But it’s not so easy to do without the parasympathetic nervous system. People who have undergone such an operation and find themselves outside the protective conditions of a hospital or laboratory adapt very poorly to the environment. They cannot regulate body temperature when exposed to heat or cold; when they lose blood, their blood pressure regulation is disrupted, and fatigue quickly develops with any intense muscle activity.
Diffuse nervous system of the intestine
Recent research has revealed the existence of a third important division of the autonomic nervous system - diffuse nervous system of the intestine. This department is responsible for the innervation and coordination of the digestive organs. Its work is independent of the sympathetic and parasympathetic systems, but can be modified under their influence. This is an additional link that connects the autonomic postganglionic nerves with the glands and muscles of the gastrointestinal tract.
The ganglia of this system innervate the intestinal walls. Axons from these ganglion cells cause contractions of the circular and longitudinal muscles that push food through the gastrointestinal tract, a process called peristalsis. Thus, these ganglia determine the characteristics of local peristaltic movements. When the food mass is inside the intestine, it slightly stretches its walls, which causes a narrowing of the area located slightly higher along the intestine and relaxation of the area located just below. As a result, the food mass is pushed further. However, under the influence of parasympathetic or sympathetic nerves, the activity of the intestinal ganglia can change. Activation of the parasympathetic system increases peristalsis, and the sympathetic system weakens it.
The mediator that excites the smooth muscles of the intestine is acetylcholine. However, the inhibitory signals leading to relaxation appear to be transmitted by a variety of substances, of which only a few have been studied. Among the intestinal neurotransmitters, there are at least three that also act in the central nervous system: somatostatin(see below), endorphins and substance P (see Chapter 6).
Central regulation of the functions of the autonomic nervous system
The central nervous system exerts much less control over the autonomic system than over the sensory or skeletal motor systems. The areas of the brain most associated with autonomic functions are hypothalamus And brain stem, especially that part of it that is located directly above the spinal cord - medulla. It is from these areas that the main pathways to the sympathetic and parasympathetic preganglionic autonomic neurons at the spinal level come.
Hypothalamus. The hypothalamus is one of the regions of the brain, the general structure and organization of which is more or less similar in representatives of different classes of vertebrates.
In general, it is generally accepted that the hypothalamus is the focus of visceral integrative functions. Signals from the neural systems of the hypothalamus directly enter networks that excite the preganglionic portions of the autonomic nerve pathways. In addition, this region of the brain exercises direct control over the entire endocrine system through specific neurons that regulate the secretion of hormones from the anterior pituitary gland, and the axons of other hypothalamic neurons terminate in the posterior pituitary gland. Here these endings release mediators that circulate in the blood as hormones: 1) vasopressin, which increases blood pressure in emergency cases when fluid or blood loss occurs; it also reduces the excretion of water in the urine (this is why vasopressin is also called antidiuretic hormone); 2) oxytocin, stimulating uterine contractions at the final stage of labor.
Although there are several clearly demarcated nuclei among the clusters of hypothalamic neurons, most of the hypothalamus is a collection of zones with blurred boundaries (Fig. 65). However, in three zones there are quite pronounced nuclei. We will now consider the functions of these structures.
1. Periventricular zone directly adjacent to the third cerebral ventricle, which passes through the center of the hypothalamus. The cells lining the ventricle convey information to the neurons of the periventricular zone about important internal parameters that may require regulation, such as temperature, salt concentration, levels of hormones secreted by the thyroid gland, adrenal glands or gonads in accordance with instructions from the pituitary gland.
2. Medial zone contains most of the pathways through which the hypothalamus exerts endocrine control through the pituitary gland. Very roughly, we can say that the cells of the periventricular zone control the actual execution of commands given to the pituitary gland by the cells of the medial zone.
3. Through cells lateral zone The hypothalamus is controlled by higher levels of the cerebral cortex and limbic system. It also receives sensory information from the centers of the medulla oblongata, which coordinate respiratory and cardiovascular activity. The lateral zone is the place where higher brain centers can make adjustments to the hypothalamus' reactions to changes in the internal environment. In the cortex, for example, there is a comparison of information coming from two sources - the internal and external environment. If, say, the cortex judges that the time and circumstances are inappropriate for eating, the sensory report of low blood sugar and an empty stomach will be put aside until a more favorable moment. The hypothalamus is less likely to be ignored by the limbic system. Rather, this system may add emotional and motivational overtones to the interpretation of external sensory signals or compare the representation of the environment based on these signals with similar situations that occurred in the past.
Rice. 65. Hypothalamus and pituitary gland. The main functional areas of the hypothalamus are shown schematically.
Together with the cortical and limbic components, the hypothalamus also performs many routine integrating actions, and over much longer periods of time than when carrying out short-term regulatory functions. The hypothalamus “knows” in advance what needs the body will have during the normal daily rhythm of life. For example, it brings the endocrine system into full readiness for action as soon as we wake up. It also monitors the hormonal activity of the ovaries throughout the menstrual cycle; takes measures to prepare the uterus for the arrival of a fertilized egg. In migratory birds and hibernating mammals, the hypothalamus, with its ability to determine the length of daylight hours, coordinates the body's vital functions during cycles lasting several months. (These aspects of centralized regulation of internal functions will be discussed in Chapters 5 and 6.)
Rice. 66.Here is a schematic representation of the various functions of the medulla oblongata. The connections coming from various internal organs to the brain stem and reticular formation are shown. Sensory signals emanating from these organs regulate the degree of activity and attention with which the brain responds to external events. Such signals also trigger specific behavioral programs with the help of which the body adapts to changes in the internal environment.
Medulla. The hypothalamus makes up less than 5% of the total brain mass. However, this small amount of tissue contains centers that support all body functions, with the exception of spontaneous breathing movements, regulation of blood pressure and heart rhythm. These latter functions depend on the medulla oblongata (see Fig. 66). With traumatic brain injuries, the so-called “brain death” occurs when all signs of electrical activity of the cortex disappear and control by the hypothalamus and medulla oblongata is lost, although with the help of artificial respiration it is still possible to maintain sufficient saturation of the circulating blood with oxygen.
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Functions of the autonomic nervous system, its divisions (sympathetic and parasympathetic), location of the main centers.
Definition
Autonomic (or autonomic) nervous system is part of the peripheral nervous system that is responsible for regulating unconscious body functions such as heartbeat, blood flow, breathing and digestion.
This system is divided into two branches: the parasympathetic and sympathetic systems. The centers of these systems are subordinate to the centers of the autonomic nervous system located in the hypothalamus, and the highest control of this system occurs in the centers of the cerebral hemispheres. They keep the effects of the parasympathetic and sympathetic systems in balance.
Sympathetic department controls responses to emergency situations. It relaxes the bladder, speeds up the heartbeat, dilates the pupils, stops digestion, reduces salivation, speeds up breathing and dilates the bronchi and bronchioles. The centers of this system are located in the lumbar and thoracic parts of the spinal cord.
Parasympathetic Division helps maintain body functions in its normal state and preserves physical resources. It controls the bladder, slows the heartbeat, constricts the pupils, stimulates digestion, increases salivation, calms breathing and constricts the bronchi and bronchioles. The vagus nerve, which runs from the lower surface of the brain to the abdominal cavity, is the main nerve of the parasympathetic nervous system - it transmits its influence to the organs of the body. The centers of this system are in the sacral parts of the spinal cord, as well as in parts of the brain (medulla oblongata and midbrain).
Reflex arcs
In the autonomic, as well as in the somatic nervous system, reflex arcs are present. The autonomic reflex arc transmits signals from the spinal cord to the organs, bypassing the brain - i.e. unconsciously, the result of such transmission is an autonomic reflex. An example of an autonomic reflex is salivation.
The autonomic division of the nervous system is that part of the unified nervous system that regulates metabolism, the functioning of internal organs, the heart, blood vessels and exocrine and internal secretion glands, and smooth muscles. It should be borne in mind that the function of regulating all vital functions of the body is carried out by the central nervous system and especially its higher department - the cerebral cortex.
This part of the nervous system received the name “vegetative” due to the fact that it is related to the work of those organs that perform functions inherent in plants (from the Latin vegitas - plant), that is, respiration, nutrition, excretion, reproduction, exchange substances. In addition, this system is sometimes inappropriately called “autonomous”. This name emphasizes that although the autonomic nervous system is subordinate to the cerebral cortex, unlike the peripheral nervous system, it does not depend on the will of the animal. Indeed, if the movement of the body is under the control of the will of the animal, then the movement of the internal organs and the work of the glands occur independently of its will.
The function of the autonomic nervous system is also based on the reflex arc. However, its sensitive links have not yet been sufficiently studied.
Rice. 292. Scheme of the structure of a segment of the autonomic nervous system in connection with the spinal cord:
/ - gray and white medulla of the spinal cord; 3 - motor fibers; 4 - ventral root; 5 - preganglionic fiber of the neuron; 5 - white connecting branch; 7 - boundary shaft unit; 8 - borderline sympathetic trunk; 9 - intramural ganglia in the intestinal wall; 10 - lateral column of gray medulla; // - sensitive fibers; 12 - dorsal root of the spinal ganglion; 13 - mixed spinal nerve; 14 - gray connecting branch; 15 - postganglionic fiber of the neuron to the vessels; 16 - prevertebral ganglion; 17 - postganglinonar fiber of the neuron to the viscera; X - vagus.
The autonomic division of the nervous system is divided into two parts - sympathetic and parasympathetic. Each internal organ is innervated by both. However, they often act differently on the organ. If one intensifies the work of the organ, then the other, on the contrary, slows it down. Thanks to this action, the organ completely adapts to the demands of the moment. Thus, with an increase in the amount of roughage, intestinal motility increases, and with a decrease in it, it weakens; when the illumination increases, the pupil contracts, when it darkens, it expands, etc. Only when both seemingly mutually exclusive effects are maintained, the organ functions normally*.
In the autonomic part of the nervous system (both sympathetic and parasympathetic parts) there are (Fig. 292): 1) centers located in different parts of the central nervous system and representing a cluster
Rice. 293. Scheme of the autonomic nervous system of cattle
(according to I.P. Osipov):
A - centers of the parasympathetic part of the nervous system (in the sacral part of the spinal cord); B - centers of the sympathetic part of the nervous system (in the lumbar-thoracic region of the spinal cord); B - spinal cord; centers of the parasympathetic part of the nervous system in the medulla oblongata; G - center of the vagus nerve; D - salivary and lacrimal centers; E - center of the parasympathetic part of the nervous system (in the midbrain); 1 - parasympathetic pathways to the organs of the pelvic cavity and the caudal part of the abdominal cavity; 2 - borderline sympathetic trunk; 3 - caudal mesenteric node; 4 - vertebral ganglia; 5 - semilunar node (center of the solar plexus); 6 - small splanchnic nerve; 7 - great splanchnic nerve; 8 - vagus nerve; 9 -- star knot; 10 - middle cervical node; 11 - spinal nerve; 12 - vagosympati-kus; 13-cranial cervical ganglion; 14 - rectum; 15 - vagina and uterus; 16-bladder; 17 - ovary; 18 - jejunum; 19 -- kidney with adrenal gland; 20 - spleen; 21 - duodenum; 22 - pancreas; 23-stomach; 24 - liver; 25 - diaphragm; 26 - lungs; 27 - heart; 28 - salivary glands; 29 - lacrimal gland; 30 - sphincter of the pupil.
Lesion of nerve cell bodies; 2) preganglionic fibers (4), which are a complex of neurites of the nerve cells mentioned above; 3) ganglia (7), into which preganglionic fibers enter and where they enter into a synaptic connection with the dendrites of ganglion cells; 4) postganglionic fibers (15, /7), which are neurites of ganglion cells and are directed to the innervated organ; 5) nerve plexuses (Fig. 293). Preganglionic and postganglionic fibers differ not only topographically, but also in structure. Preganglionic fibers are usually covered with a myelin sheath and are therefore white. Postganglionic fibers lack this sheath, are gray in color, and slowly conduct excitation.
Sympathetic part of the autonomic nervous system
The sympathetic part of the autonomic nervous system is developed differently in different classes of chordates. Thus, no elements of the system were found in the lancelet. In cyclostomes, it is represented by two rows of ganglia segmentally located on the sides of the aorta, which are not connected to each other, but are in connection with the spinal nerves on one side and with the viscera and heart on the other side. In the internal organs, sympathetic branches form plexuses that unite the ganglia, with ganglion cells. The same cells are found in the walls of the animal body along the motor and sensory somatic nerves. In bony fishes, sympathetic paired ganglia are also located in the head region. In this case, all the trunk ganglia on each side of the animal’s body are connected to each other into two long paired cords, forming two sympathetic border trunks. The ganglia that make up this trunk connect on one side with the spinal nerves, on the other side with the viscera, forming plexuses in them. Fibers going from the spinal cord to the vertebral ganglia are called pre-ganglionic, and from the ganglia to the organs - postganglionic. The right and left border sympathetic trunks are not connected to each other.
In higher vertebrates, starting with tailless amphibians, the caudal, sometimes sacral and even lumbar sections of the borderline sympathetic trunk are less developed and are partially or completely connected in the caudal section. It is assumed that during the process of phylogenesis in vertebrates, individual nerve cells are evicted from the spinal ganglia, which are located in the subbodies of the vertebrae and form the vertebral sympathetic ganglia. They are also connected to each other, to the spinal cord and to the organs innervated by them, forming plexuses.
The sympathetic system of mammals is composed of: 1) centers, which are the bodies of nerve cells located in the central nervous system; 2) preganglionic fibers, which are processes of the cells of the center of the sympathetic nervous system, which reach 3) numerous ganglia of the sympathetic nervous system, and 4) postganglionic fibers, starting from the cell bodies of the ganglia and heading to various organs and tissues (Fig. 293-1 -13).
1. The center of the sympathetic part of the autonomic nervous system is located in the lateral horns of the entire thoracic and the first two to four segments of the lumbar spinal cord (B).
2. The ganglia of the sympathetic nervous system are very numerous and form a system of right and left border sympathetic trunks, located on the sides of the vertebral bodies and called vertebral (2), and a system of unpaired prevertebral ganglia lying below the spinal column, near the abdominal aorta.
In the borderline sympathetic trunks, the cervical, thoracic, lumbar, sacral and caudal ganglia are distinguished. In this regard, although the center of the sympathetic part of the autonomic nervous system is located only in the thoracic and partially in the lumbar spinal cord, the border sympathetic trunk extends along the entire body of the animal and is divided into the head, cervical, thoracic, lumbar, sacral and caudal sections. In the cervical portion of the sympathetic nervous system in cattle and pigs there are three cervical ganglia - cranial, middle and caudal: the horse does not have a middle ganglion. In the thoracic region, the number of ganglia in most cases corresponds to the number of vertebrae, with the first thoracic ganglion often merging with the last cervical ganglion, forming the stellate ganglion (9). In the lumbar, sacral and caudal sections of the border sympathetic trunk there are also paired ganglia (I.P. Osipov).
The system of prevertebral ganglia includes: the unpaired semilunar ganglion, in turn consisting of one cranial mesenteric and two celiac ganglia, fused together, and a caudal mesenteric ganglion. The semilunar ganglion lies on the aorta and covers with its ends the base of the celiac and cranial mesenteric arteries, which arise from the aorta. The caudal mesenteric ganglion is located at the base of the caudal mesenteric artery. They are located in the abdominal cavity.
3. Preganglionic sympathetic fibers, which are neurites of the cells of the lateral horns of the thoracic and partially lumbar spinal cord, connect the center of the sympathetic nervous system with the ganglia. Preganglionic fibers exit the spinal cord as part of the ventral root of the spinal nerve (Fig. 292-5). Coming out of the spinal canal together with the spinal nerve, they soon separate from it and enter into a symplastic connection with the dendrites ™™"™"™™"* others simply pass through them, heading back or forward to the next ganglion, and end already in it or go even further. Thanks to this, the vertebral sympathetic ganglia are connected with each other in the border trunk of the sympathetic nervous system, which in cattle reaches the seventh caudal vertebra. Since the cranial cervical ganglion lies at the base of the head near the atlas wing, and caudal neck in the area of the last cervical vertebra, then the anglionic fibers connecting them have a significant length. Uniting together with the vagus nerve, they form the n. vagosympaticus.
Finally, part of the preganglionic fibers is directed caudally and, having passed through the last few thoracic ganglia, the second splanchnicus major nerve (Fig. 293-7) and the small Gutrenunorstny Nerve n. splanchicus minor (6). The first of these in cattle" and pigs it is formed" due to the neurites of the cells of the lateral horns of the VT XII a v horse of the VI-XV thoracic segments, and the second - due to three subsequent ^oGn^ passing "t" through the diaphragm from the thoracic stripes - abdominal and enter the semilunar ganglion. Most of the preganglionic fibers of these nerves end in the semilunar ganglion, but a large number of them are sent, apparently, to the caudal mesenteric glia, into which preganglionic fibers also enter from the lumbar funnels and p^Y RH. Mindubaeva , is the cervical part of the borderline sym-PaTIGheadS™gaanglionic fibers extend from the cranial cervical
The nervous system gives only gray connecting branches to the spinal nerves of its area.
Numerous postganglionic fibers depart from the semilunar ganglion, which, before entering the organ they innervate, branch and intertwine with each other, forming numerous plexuses: gastric, hepatic, splenic, cranial mesenteric, renal and adrenal. The four splanchnic nerves entering the semilunar ganglion (right and left major and right and left minor) and numerous postganglionic nerve fibers emerging from it diverge from the semilunar ganglion along radii, like rays from the disk of the sun, which gave rise to calling this part of the sympathetic system the solar plexus - plexus Solaris (Fig. 293-5).
From the caudal mesenteric ganglion, postganglionic fibers are sent to the caudal part of the intestine, as well as to the organs of the pelvic cavity. These fibers also form a number of plexuses: the caudal mesenteric, internal testicular (ovarian), form the hypogastric nerve with the hypogastric plexus, the genital plexus of the penis, the vesical, hemorrhoidal and a number of others.
Parasympathetic part of the autonomic nervous system
The parasympathetic part of the autonomic part of the nervous system differs from the sympathetic part of the same part mainly in the location of its centers, in less anatomical isolation, in many cases in a different effect on the same organ, aimed, however, at ensuring its better performance, as well as that its ganglia are either very close to the centers, or, conversely, at a very far distance from them. Functionally, they are united and ensure the functioning of the body in connection with its various conditions.
The parasympathetic part of the autonomic nervous system consists of a central part, preganglionic fibers, ganglia and postganglionic fibers (Fig. 293-L, D, E, F).
The center of the parasympathetic system is located in the midbrain and medulla oblongata, as well as in the lateral horns of the sacral spinal cord. In this regard, it is divided into the head and sacral sections; in this case, the first, in turn, is divided into midbrain and medulla oblongata.
In the midbrain region, the center is located in the area of the oral tubercles of the quadrigeminal, from where preganglionic parasympathetic fibers emerge as part of the oculomotor nerve and reach the ciliary ganglion. From it, postganglionic parasympathetic (and sympathetic) fibers that join them pass through other nerves to the eyeball and branch in the sphincter of the pupil and in the ciliary muscle, consisting of smooth muscle tissue. Sympathetic nerves cause pupil dilation; parasympathetic, on the contrary, narrows it (E).
The medulla oblongata of the parasympathetic nervous system has several centers. In accordance with this, four directions or paths are noted in it: lacrimal, two salivary and visceral (to the insides) (D, E).
1. The lacrimal duct has a center at the bottom of the fourth cerebral ventricle, from where preganglionic parasympathetic fibers enter the facial nerve and reach the sphenopalatine ganglion, which lies in the fossa of the same name. From this node, postganglionic parasympathetic (and sympathetic) fibers joining them are directed along other cranial nerves to the lacrimal glands, and partly to the glands of the mucous membrane of the palate and nasal cavity. 2. The oral salivary tract begins at the bottom of the fourth cerebral ventricle. The preganglionic parasympathetic fibers of this pathway exit the skull as part of the facial nerve and enter the sublingual, or submandibular, ganglion, located medial to the sublingual salivary gland. From this node, postganglionic parasympathetic fibers (together with sympathetic ones) are sent to the submandibular and sublingual salivary glands of their sides. 3. The center of the second salivary tract lies somewhat more aboral than the first. The preganglionic parasympathetic fibers of this pathway, as part of the glossopharyngeal nerve, reach the ear ganglion, located near the foramen lacerum. From the auricular ganglion, parasympathetic postganglionic fibers go to the parotid salivary gland and the buccal and labial glands. 4. The visceral pathway, that is, for the viscera, ensures the motor and secretory activity of the internal organs of the thoracic and abdominal cavity. The center of this pathway is the nuclei of the vagus nerve, located in the bottom of the rhomboid fossa of the medulla oblongata. Preganglionic fibers, which are the neurites of the cells of these nuclei, form the bulk of the vagus nerve. However, it also contains somatic (non-vegetative) fibers.
From the cranial cavity, the vagus nerve - p. vagus - exits through the posterior edge of the foramen lacerum and is directed along the neck through the chest cavity into the abdominal cavity. The vagus nerve is conventionally divided into cervical, thoracic and abdominal parts. Its cervical part (8) is combined with the cervical portion of the sympathetic border trunk into one common trunk - the vagosympaticus. The thoracic part of the vagus nerve separates from the sympathetic border trunk, gives off the recurrent nerve (somatic fibers) to the pharynx and larynx, as well as a number of parasympathetic branches to various organs located in the thoracic cavity, and is divided into dorsal and ventral branches running along the esophagus. Numerous branches of the vagus nerve in the thoracic cavity, combining with sympathetic fibers, form various plexuses innervating the esophagus, heart, blood vessels, trachea, lungs, etc. Subsequently, the dorsal branches of the vagus nerve on the right and left sides merge into one dorsal esophageal trunk, and ventral - into the ventral esophageal trunk, which pass through the diaphragm into the abdominal cavity. The abdominal part of the vagus nerve is anatomically traced to the solar plexus, and its physiological action extends to all organs innervated from the solar plexus. The preganglionic fibers that make up the vagus end in ganglia located inside the wall of the innervated organ. Due to their position, these ganglia are called intramural. They are detected only histologically. The postganglionic fibers of the vagus are short and end near the ganglion, innervating the glandular tissue and smooth muscles of the organs: stomach, liver, pancreas, all the intestines of the small section and most of the intestines of the large section.
In the sacral (sacral) part of the parasympathetic part of the autonomic nervous system, the center lies in the lateral horns of the sacral part of the spinal cord. The preganglionic parasympathetic fibers of this area exit with the first three or second to fourth pairs of sacral nerves. Coming out of the spinal canal, the parasympathetic fibers separate from the spinal nerves and form the pelvic nerve - n. pelvicus, or pelvic nerve, which innervates the end of the colon, rectum, bladder and genitals.
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