The nervous regulation of the work of the heart is carried out by sympathetic and parasympathetic impulses. The former increase the frequency, strength of contractions, blood pressure, and the latter have the opposite effect. Age-related changes in the tone of the autonomic nervous system are taken into account when prescribing treatment.

The sympathetic nervous system is designed to activate all body functions in a stressful situation. It provides a fight-or-flight response. Under the influence of irritation of the nerve fibers that enter it, the following changes occur:

weak bronchospasm;
narrowing of the arteries, arterioles, especially those located in the skin, intestines and kidneys;
contraction of the uterus, bladder sphincters, spleen capsule;
spasm of the rainbow muscle, pupil dilation;
decrease in motor activity and tone of the intestinal wall;
accelerated .

Strengthening of all cardiac functions - excitability, conductivity, contractility, automatism, splitting of adipose tissue and the release of renin by the kidneys (increases pressure) are associated with irritation of beta-1 adrenoreceptors. And stimulation of beta-2 type leads to:

expansion of the bronchi;
relaxation of the muscular wall of arterioles in the liver and muscles;
breakdown of glycogen;
the release of insulin to carry glucose into cells;
energy generation;
decrease in uterine tone.

The sympathetic system does not always have a unidirectional effect on the organs, which is associated with the presence of several types of adrenergic receptors in them. Ultimately, the tolerance of physical and mental stress increases in the body, the work of the heart and skeletal muscles increases, and blood circulation is redistributed to nourish vital organs.

What is the difference between the parasympathetic system

This section of the autonomic nervous system is designed to relax the body, recover from exercise, ensure digestion and energy storage. When the vagus nerve is activated:

increased blood flow to the stomach and intestines;
increased release of digestive enzymes and bile production;
the bronchi narrow (at rest, a lot of oxygen is not required);
the rhythm of contractions slows down, their strength decreases;
decreases the tone of the arteries and.

Influence of two systems on the heart

Despite the fact that sympathetic and parasympathetic stimulation have opposite effects on the cardiovascular system, this is not always so clear-cut. And the mechanisms of their mutual influence do not have a mathematical pattern, not all of them have been sufficiently studied, but it has been established:

the more the sympathetic tone rises, the stronger the inhibitory effect of the parasympathetic department will be - the accentuated opposition;
when the desired result is achieved (for example, acceleration of the rhythm during exercise), the sympathetic and parasympathetic influence is inhibited - functional synergism (unidirectional action);
the higher the initial level of activation, the less the possibility of its increase during stimulation - the law of the initial level.

Watch the video about the effect on the heart of the sympathetic and parasympathetic systems:

Effect of age on autonomic tone

In newborns, the influence of the sympathetic department predominates against the background of a general immaturity of nervous regulation. Therefore, they are significantly accelerated. Then both parts of the autonomic system develop very rapidly, reaching a maximum by adolescence. At this time, the highest concentration of nerve plexuses in the myocardium is noted, which explains the rapid change in pressure and contraction rate under external influences.

Up to 40 years, parasympathetic tone prevails, which affects the slowing of the pulse at rest and its rapid return to normal after exercise. And then age-related changes begin - the number of adrenoreceptors decreases while maintaining the parasympathetic ganglia. This leads to the following processes:

the excitability of muscle fibers worsens;
the processes of formation of impulses are violated;
increases the sensitivity of the vascular wall and myocardium to the action of stress hormones.

Under the influence of ischemia, the cells acquire an even greater response to sympathetic impulses and respond to even the slightest signals with spasm of the arteries and an acceleration of the pulse. At the same time, the electrical instability of the myocardium increases, which explains the frequent occurrence with, and especially with.

It has been proven that disturbances in sympathetic innervation are many times greater than the destruction zone in acute coronary circulation disorders.

What happens when aroused

In the heart, there are mainly beta 1 adrenoreceptors, a little beta 2 and alpha type. At the same time, they are located on the surface of cardiomyocytes, which increases their availability for the main mediator (conductor) of sympathetic impulses - norepinephrine. Under the influence of activation of receptors, the following changes occur:

the excitability of the cells of the sinus node, the conduction system, muscle fibers increases, they even respond to subthreshold signals;
conduction of an electrical impulse is accelerated;
the amplitude of contractions increases;
the number of heartbeats per minute increases.

Parasympathetic cholinergic receptors of type M were also found on the outer membrane of the heart cells. Their excitation inhibits the activity of the sinus node, but at the same time increases the excitability of the atrial muscle fibers. This can explain the development of supraventricular extrasystole at night, when the tone of the vagus nerve is high.

The second depressive effect is the inhibition of the parasympathetic conduction system in the atrioventricular node, which delays the propagation of signals to the ventricles.

Thus, the parasympathetic nervous system:

reduces the excitability of the ventricles and increases it in the atria;
slows down the heart rate;
inhibits the formation and conduction of impulses;
suppresses the contractility of muscle fibers;
reduces myocardial oxygen demand;
prevents spasm of the walls of arteries and.

Sympathicotonia and vagotonia

Depending on the predominance of the tone of one of the divisions of the autonomic nervous system, patients may have an initial increase in sympathetic effects on the heart - sympathicotonia and vagotonia with excessive parasympathetic activity. This is important when prescribing treatment for diseases, since the reaction to medications can be different.

For example, with initial sympathicotonia, patients can be identified:

the skin is dry and pale, the extremities are cold;
the pulse is accelerated, the increase in systolic and pulse pressure predominates;
sleep is disturbed;
psychologically stable, active, but there is high anxiety.

For such patients, it is necessary to use sedative drugs and adrenoblockers as the basis of drug therapy. With vagotonia, the skin is moist, there is a tendency to faint with a sharp change in body position, movements are slowed down, exercise tolerance is low, the difference between systolic and diastolic pressure is reduced.

For therapy, it is advisable to use calcium antagonists,.

Sympathetic nerve fibers and the neurotransmitter norepinephrine ensure the activity of the body under the action of stress factors. With the stimulation of adrenoreceptors, the pressure rises, the pulse accelerates, the excitability and conduction of the myocardium increase.

The parasympathetic division and acetylcholine have an opposite effect on the heart, they are responsible for relaxation and energy accumulation. Normally, these processes successively replace each other, and in case of violation of the nervous regulation (sympathicotonia or vagotonia), the blood circulation parameters change.

AUTONOMIC SYSTEM

The autonomic (autonomous) nervous system regulates all the internal processes of the body: the functions of internal organs and systems, glands, blood and lymphatic vessels, smooth and partially striated muscles, sensory organs (Fig. 6.1). It provides homeostasis of the body, i.e. the relative dynamic constancy of the internal environment and the stability of its basic physiological functions (blood circulation, respiration, digestion, thermoregulation, metabolism, excretion, reproduction, etc.). In addition, the autonomic nervous system performs an adaptive-trophic function - the regulation of metabolism in relation to environmental conditions.

The term "autonomic nervous system" reflects the control of the involuntary functions of the body. The autonomic nervous system is dependent on the higher centers of the nervous system. There is a close anatomical and functional relationship between the autonomic and somatic parts of the nervous system. Autonomic nerve conductors pass through the cranial and spinal nerves. The main morphological unit of the autonomic nervous system, as well as the somatic one, is the neuron, and the main functional unit is the reflex arc. In the autonomic nervous system, there are central (cells and fibers located in the brain and spinal cord) and peripheral (all its other formations) sections. There are also sympathetic and parasympathetic parts. Their main difference lies in the features of functional innervation and is determined by the attitude to the means that affect the autonomic nervous system. The sympathetic part is excited by adrenaline, and the parasympathetic part by acetylcholine. Ergotamine has an inhibitory effect on the sympathetic part, and atropine on the parasympathetic part.

6.1. Sympathetic division of the autonomic nervous system

Central formations are located in the cerebral cortex, hypothalamic nuclei, brain stem, in the reticular formation, and also in the spinal cord (in the lateral horns). The cortical representation is not sufficiently elucidated. From the cells of the lateral horns of the spinal cord at the level from C VIII to L V, peripheral formations of the sympathetic division begin. The axons of these cells pass as part of the anterior roots and, having separated from them, form a connecting branch that approaches the nodes of the sympathetic trunk. This is where part of the fibers ends. From the cells of the nodes of the sympathetic trunk, the axons of the second neurons begin, which again approach the spinal nerves and end in the corresponding segments. The fibers that pass through the nodes of the sympathetic trunk, without interruption, approach the intermediate nodes located between the innervated organ and the spinal cord. From the intermediate nodes, the axons of the second neurons begin, heading to the innervated organs.

Rice. 6.1.

1 - cortex of the frontal lobe of the brain; 2 - hypothalamus; 3 - ciliary knot; 4 - pterygopalatine node; 5 - submandibular and sublingual nodes; 6 - ear knot; 7 - upper cervical sympathetic node; 8 - large splanchnic nerve; 9 - internal node; 10 - celiac plexus; 11 - celiac nodes; 12 - small splanchnic nerve; 12a - lower splanchnic nerve; 13 - superior mesenteric plexus; 14 - lower mesenteric plexus; 15 - aortic plexus; 16 - sympathetic fibers to the anterior branches of the lumbar and sacral nerves for the vessels of the legs; 17 - pelvic nerve; 18 - hypogastric plexus; 19 - ciliary muscle; 20 - sphincter of the pupil; 21 - pupil dilator; 22 - lacrimal gland; 23 - glands of the mucous membrane of the nasal cavity; 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 (muscle that ejects urine); 41 - sphincter of the bladder; 42 - gonads; 43 - genitals; III, XIII, IX, X - cranial nerves

The sympathetic trunk is located along the lateral surface of the spine and has 24 pairs of sympathetic nodes: 3 cervical, 12 thoracic, 5 lumbar, 4 sacral. From the axons of the cells of the upper cervical sympathetic ganglion, the sympathetic plexus of the carotid artery is formed, from the lower - the upper cardiac nerve, which forms the sympathetic plexus in the heart. The aorta, lungs, bronchi, abdominal organs are innervated from the thoracic nodes, and the pelvic organs are innervated from the lumbar nodes.

6.2. Parasympathetic division of the autonomic nervous system

Its formations begin from the cerebral cortex, although the cortical representation, as well as the sympathetic part, has not been sufficiently elucidated (mainly it is the limbic-reticular complex). There are mesencephalic and bulbar sections in the brain and sacral - in the spinal cord. The mesencephalic section includes the nuclei of the cranial nerves: the third pair is the accessory nucleus of Yakubovich (paired, small cell), which innervates the muscle that narrows the pupil; Perlia's nucleus (unpaired small cell) innervates the ciliary muscle involved in accommodation. The bulbar section consists of the upper and lower salivary nuclei (VII and IX pairs); X pair - the vegetative nucleus that innervates the heart, bronchi, gastrointestinal tract,

his digestive glands, other internal organs. The sacral section is represented by cells in segments S II -S IV, the axons of which form the pelvic nerve that innervates the urogenital organs and the rectum (Fig. 6.1).

Under the influence of both the sympathetic and parasympathetic divisions of the autonomic nervous system are all organs, with the exception of blood vessels, sweat glands and the adrenal medulla, which have only sympathetic innervation. The parasympathetic department is more ancient. As a result of its activity, stable states of organs and conditions for creating reserves of energy substrates are created. The sympathetic part changes these states (i.e., the functional abilities of organs) in relation to the function being performed. Both parts work in close cooperation. Under certain conditions, the functional predominance of one part over the other is possible. In the case of the predominance of the tone of the parasympathetic part, a state of parasympathotonia develops, the sympathetic part - sympathotonia. Parasympathotonia is characteristic of the state of sleep, sympathotonia - for affective states (fear, anger, etc.).

In clinical conditions, conditions are possible in which the activity of individual organs or body systems is disrupted as a result of the predominance of the tone of one of the parts of the autonomic nervous system. Parasympathotonic manifestations accompany bronchial asthma, urticaria, angioedema, vasomotor rhinitis, motion sickness; sympathotonic - vasospasm in the form of Raynaud's syndrome, migraine, transient form of hypertension, vascular crises in hypothalamic syndrome, ganglionic lesions, panic attacks. The integration of vegetative and somatic functions is carried out by the cerebral cortex, the hypothalamus and the reticular formation.

6.3. Limbico-reticular complex

All activity of the autonomic nervous system is controlled and regulated by the cortical parts of the nervous system (frontal cortex, parahippocampal and cingulate gyrus). The limbic system is the center of emotion regulation and the neural substrate of long-term memory. The rhythm of sleep and wakefulness is also regulated by the limbic system.

Rice. 6.2. limbic system. 1 - corpus callosum; 2 - vault; 3 - belt; 4 - posterior thalamus; 5 - isthmus of the cingulate gyrus; 6 - III ventricle; 7 - mastoid body; 8 - bridge; 9 - lower longitudinal beam; 10 - border; 11 - gyrus of the hippocampus; 12 - hook; 13 - orbital surface of the frontal pole; 14 - hook-shaped bundle; 15 - transverse connection of the amygdala; 16 - front spike; 17 - anterior thalamus; 18 - cingulate gyrus

The limbic system (Fig. 6.2) is understood as a number of closely interconnected cortical and subcortical structures that have common development and functions. It also includes the formation of the olfactory pathways located at the base of the brain, the transparent septum, the vaulted gyrus, the cortex of the posterior orbital surface of the frontal lobe, the hippocampus, and the dentate gyrus. The subcortical structures of the limbic system include the caudate nucleus, the putamen, the amygdala, the anterior tubercle of the thalamus, the hypothalamus, and the nucleus of the frenulum. The limbic system includes a complex interweaving of ascending and descending pathways, closely associated with the reticular formation.

Irritation of the limbic system leads to the mobilization of both sympathetic and parasympathetic mechanisms, which has corresponding vegetative manifestations. A pronounced vegetative effect occurs when the anterior parts of the limbic system are irritated, in particular the orbital cortex, amygdala and cingulate gyrus. At the same time, there are changes in salivation, respiratory rate, increased intestinal motility, urination, defecation, etc.

Of particular importance in the functioning of the autonomic nervous system is the hypothalamus, which regulates the functions of the sympathetic and parasympathetic systems. In addition, the hypothalamus implements the interaction of nervous and endocrine, the integration of somatic and autonomic activity. The hypothalamus contains specific and nonspecific nuclei. Specific nuclei produce hormones (vasopressin, oxytocin) and releasing factors that regulate the secretion of hormones from the anterior pituitary gland.

Sympathetic fibers that innervate the face, head and neck originate from cells located in the lateral horns of the spinal cord (C VIII -Th III). Most of the fibers are interrupted in the superior cervical sympathetic ganglion, and a smaller part goes to the external and internal carotid arteries and forms periarterial sympathetic plexuses on them. They are joined by postganglionic fibers coming from the middle and lower cervical sympathetic nodes. In small nodules (cell clusters) located in the periarterial plexuses of the branches of the external carotid artery, fibers terminate that are not interrupted at the nodes of the sympathetic trunk. The remaining fibers are interrupted in the facial ganglia: ciliary, pterygopalatine, sublingual, submandibular and auricular. Postganglionic fibers from these nodes, as well as fibers from the cells of the upper and other cervical sympathetic nodes, go to the tissues of the face and head, partly as part of the cranial nerves (Fig. 6.3).

Afferent sympathetic fibers from the head and neck are sent to the periarterial plexuses of the branches of the common carotid artery, pass through the cervical nodes of the sympathetic trunk, partially contacting their cells, and through the connecting branches come to the spinal nodes, closing the arc of the reflex.

Parasympathetic fibers are formed by axons of the stem parasympathetic nuclei, they are directed mainly to the five autonomic ganglia of the face, in which they are interrupted. A smaller part of the fibers goes to the parasympathetic clusters of cells of the periarterial plexuses, where it is also interrupted, and the postganglionic fibers go as part of the cranial nerves or periarterial plexuses. In the parasympathetic part there are also afferent fibers that go in the vagus nerve system and are sent to the sensory nuclei of the brainstem. The anterior and middle sections of the hypothalamic region through the sympathetic and parasympathetic conductors affect the function of the predominantly ipsilateral salivary glands.

6.5. Autonomic innervation of the eye

sympathetic innervation. Sympathetic neurons are located in the lateral horns of segments C VIII -Th III of the spinal cord. (centrun ciliospinale).

Rice. 6.3.

1 - posterior central nucleus of the oculomotor nerve; 2 - accessory nucleus of the oculomotor nerve (nucleus of Yakubovich-Edinger-Westphal); 3 - oculomotor nerve; 4 - nasociliary branch from the optic nerve; 5 - ciliary knot; 6 - short ciliary nerves; 7 - sphincter of the pupil; 8 - pupil dilator; 9 - ciliary muscle; 10 - internal carotid artery; 11 - carotid plexus; 12 - deep stony nerve; 13 - upper salivary nucleus; 14 - intermediate nerve; 15 - knee assembly; 16 - large stony nerve; 17 - pterygopalatine node; 18 - maxillary nerve (II branch of the trigeminal nerve); 19 - zygomatic nerve; 20 - lacrimal gland; 21 - mucous membranes of the nose and palate; 22 - knee-tympanic nerve; 23 - ear-temporal nerve; 24 - middle meningeal artery; 25 - parotid gland; 26 - ear knot; 27 - small stony nerve; 28 - tympanic plexus; 29 - auditory tube; 30 - single way; 31 - lower salivary nucleus; 32 - drum string; 33 - tympanic nerve; 34 - lingual nerve (from the mandibular nerve - III branch of the trigeminal nerve); 35 - taste fibers to the anterior 2/3 of the tongue; 36 - sublingual gland; 37 - submandibular gland; 38 - submandibular node; 39 - facial artery; 40 - upper cervical sympathetic node; 41 - cells of the lateral horn ThI-ThII; 42 - the lower node of the glossopharyngeal nerve; 43 - sympathetic fibers to the plexuses of the internal carotid and middle meningeal arteries; 44 - innervation of the face and scalp. III, VII, IX - cranial nerves. Green color indicates parasympathetic fibers, red - sympathetic, blue - sensitive

The processes of these neurons, forming preganglionic fibers, exit the spinal cord together with the anterior roots, enter the sympathetic trunk as part of the white connecting branches and, without interruption, pass through the overlying nodes, ending at the cells of the superior cervical sympathetic plexus. The postganglionic fibers of this node accompany the internal carotid artery, braiding its wall, penetrate into the cranial cavity, where they connect with the I branch of the trigeminal nerve, penetrate the orbital cavity and end at the muscle that dilates the pupil (m. dilatator pupillae).

Sympathetic fibers also innervate other structures of the eye: tarsal muscles, which expand the palpebral fissure, the orbital muscle of the eye, as well as some structures of the face - sweat glands of the face, smooth muscles of the face and blood vessels.

parasympathetic innervation. The preganglionic parasympathetic neuron lies in the accessory nucleus of the oculomotor nerve. As part of the latter, it leaves the brain stem and reaches the ciliary ganglion (ganglion ciliare), where it switches to postganglionic cells. From there, part of the fibers goes to the muscle that narrows the pupil (m. sphincter pupillae), and the other part is involved in providing accommodation.

Violation of the autonomic innervation of the eye. The defeat of sympathetic formations causes the Bernard-Horner syndrome (Fig. 6.4) with pupil constriction (miosis), narrowing of the palpebral fissure (ptosis), retraction of the eyeball (enophthalmos). It is also possible to develop homolateral anhidrosis, conjunctival hyperemia, depigmentation of the iris.

The development of the Bernard-Horner syndrome is possible with the localization of the lesion at a different level - the involvement of the posterior longitudinal bundle, the paths to the muscle that dilates the pupil. The congenital variant of the syndrome is more often associated with birth trauma with damage to the brachial plexus.

When the sympathetic fibers are irritated, a syndrome occurs that is the opposite of the Bernard-Horner syndrome (Pourfour du Petit) - expansion of the palpebral fissure and pupil (mydriasis), exophthalmos.

6.6. Vegetative innervation of the bladder

The regulation of the activity of the bladder is carried out by the sympathetic and parasympathetic divisions of the autonomic nervous system (Fig. 6.5) and includes retention of urine and emptying of the bladder. Normally, retention mechanisms are more activated, which

Rice. 6.4. Right-sided Bernard-Horner syndrome. Ptosis, miosis, enophthalmos

is carried out as a result of activation of sympathetic innervation and blockade of the parasympathetic signal at the level of segments L I -L II of the spinal cord, while detrusor activity is suppressed and the tone of the muscles of the internal sphincter of the bladder increases.

Regulation of the act of urination occurs when activated

parasympathetic center at the level of S II -S IV and the center of urination in the bridge of the brain (Fig. 6.6). Descending efferent signals send signals that provide relaxation of the external sphincter, suppress sympathetic activity, remove the block of conduction along parasympathetic fibers, and stimulate the parasympathetic center. This results in contraction of the detrusor and relaxation of the sphincters. This mechanism is under the control of the cerebral cortex; the reticular formation, the limbic system, and the frontal lobes of the cerebral hemispheres take part in the regulation.

Arbitrary stop of urination occurs when a command is received from the cerebral cortex to the centers of urination in the brain stem and sacral spinal cord, which leads to a contraction of the external and internal sphincters of the pelvic floor muscles and periurethral striated muscles.

The defeat of the parasympathetic centers of the sacral region, the autonomic nerves emanating from it, is accompanied by the development of urinary retention. It can also occur when the spinal cord is damaged (trauma, tumor, etc.) at a level above the sympathetic centers (Th XI -L II). Partial damage to the spinal cord above the level of the location of the autonomic centers can lead to the development of an imperative urge to urinate. When the spinal sympathetic center (Th XI - L II) is affected, true urinary incontinence occurs.

Research methodology. There are numerous clinical and laboratory methods for studying the autonomic nervous system, their choice is determined by the task and conditions of the study. However, in all cases, it is necessary to take into account the initial vegetative tone and the level of fluctuations relative to the background value. The higher the baseline, the lower will be the response in functional tests. In some cases, even a paradoxical reaction is possible. Beam study

Rice. 6.5.

1 - cerebral cortex; 2 - fibers that provide arbitrary control over the emptying of the bladder; 3 - fibers of pain and temperature sensitivity; 4 - cross section of the spinal cord (Th IX -L II for sensory fibers, Th XI -L II for motor); 5 - sympathetic chain (Th XI -L II); 6 - sympathetic chain (Th IX -L II); 7 - cross section of the spinal cord (segments S II -S IV); 8 - sacral (unpaired) node; 9 - genital plexus; 10 - pelvic splanchnic nerves;

11 - hypogastric nerve; 12 - lower hypogastric plexus; 13 - sexual nerve; 14 - external sphincter of the bladder; 15 - bladder detrusor; 16 - internal sphincter of the bladder

Rice. 6.6.

it is better to do it in the morning on an empty stomach or 2 hours after eating, at the same time, at least 3 times. The minimum value of the received data is taken as the initial value.

The main clinical manifestations of the predominance of the sympathetic and parasympathetic systems are presented in Table. 6.1.

To assess the autonomic tone, it is possible to conduct tests with exposure to pharmacological agents or physical factors. As pharmacological agents, solutions of adrenaline, insulin, mezaton, pilocarpine, atropine, histamine, etc. are used.

Cold test. In the supine position, the heart rate is calculated and blood pressure is measured. After that, the other hand is dipped in cold water (4 °C) for 1 min, then the hand is taken out of the water and the blood pressure and pulse are recorded every minute until they return to the initial level. Normally, this happens after 2-3 minutes. With an increase in blood pressure by more than 20 mm Hg. Art. the reaction is considered pronounced sympathetic, less than 10 mm Hg. Art. - moderate sympathetic, and with a decrease in blood pressure - parasympathetic.

Oculocardial reflex (Dagnini-Ashner). When pressing on the eyeballs in healthy people, the heart rate slows down by 6-12 per minute. If the number of heart rate decreases by 12-16 per minute, this is regarded as a sharp increase in the tone of the parasympathetic part. The absence of a decrease or increase in heart rate by 2-4 per minute indicates an increase in the excitability of the sympathetic department.

solar reflex. The patient lies on his back, and the examiner presses his hand on the upper abdomen until a pulsation of the abdominal aorta is felt. After 20-30 seconds, the heart rate slows down in healthy people by 4-12 per minute. Changes in cardiac activity are assessed in the same way as when evoking an oculocardial reflex.

orthoclinostatic reflex. In a patient lying on his back, the heart rate is calculated, and then they are asked to stand up quickly (orthostatic test). When moving from a horizontal to a vertical position, the heart rate increases by 12 per minute with an increase in blood pressure by 20 mm Hg. Art. When the patient moves to a horizontal position, the pulse and blood pressure return to their original values within 3 minutes (clinostatic test). The degree of pulse acceleration during an orthostatic test is an indicator of the excitability of the sympathetic division of the autonomic nervous system. A significant slowing of the pulse during the clinostatic test indicates an increase in the excitability of the parasympathetic department.

Table 6.1.

Continuation of table 6.1.

Adrenaline test. In a healthy person, subcutaneous injection of 1 ml of a 0.1% solution of adrenaline after 10 minutes causes blanching of the skin, increased blood pressure, increased heart rate and increased blood glucose levels. If such changes occur faster and are more pronounced, then the tone of sympathetic innervation is increased.

Skin test with adrenaline. A drop of 0.1% adrenaline solution is applied to the skin injection site with a needle. In a healthy person, blanching with a pink corolla around occurs in such an area.

Atropine test. Subcutaneous injection of 1 ml of a 0.1% solution of atropine in a healthy person causes dry mouth, decreased sweating, increased heart rate and dilated pupils. With an increase in the tone of the parasympathetic part, all reactions to the introduction of atropine are weakened, so the test can be one of the indicators of the state of the parasympathetic part.

To assess the state of the functions of segmental vegetative formations, the following tests can be used.

Dermographism. Mechanical irritation is applied to the skin (with the handle of a hammer, with the blunt end of a pin). The local reaction occurs as an axon reflex. At the site of irritation, a red band appears, the width of which depends on the state of the autonomic nervous system. With an increase in sympathetic tone, the band is white (white dermographism). Wide stripes of red dermographism, a stripe rising above the skin (sublime dermographism), indicate an increase in the tone of the parasympathetic nervous system.

For topical diagnostics, reflex dermographism is used, which is irritated with a sharp object (swiped across the skin with the tip of a needle). There is a strip with uneven scalloped edges. Reflex dermographism is a spinal reflex. It disappears in the corresponding zones of innervation when the posterior roots, segments of the spinal cord, anterior roots and spinal nerves are affected at the level of the lesion, but remains above and below the affected zone.

Pupillary reflexes. Determine the direct and friendly reaction of the pupils to light, the reaction to convergence, accommodation and pain (dilation of the pupils with a prick, pinch and other irritations of any part of the body).

Pilomotor reflex caused by a pinch or by applying a cold object (a test tube with cold water) or a coolant (a cotton wool moistened with ether) to the skin of the shoulder girdle or the back of the head. On the same half of the chest, "goosebumps" appear as a result of contraction of smooth hair muscles. The arc of the reflex closes in the lateral horns of the spinal cord, passes through the anterior roots and the sympathetic trunk.

Test with acetylsalicylic acid. After taking 1 g of acetylsalicylic acid, diffuse sweating appears. With the defeat of the hypothalamic region, its asymmetry is possible. With damage to the lateral horns or anterior roots of the spinal cord, sweating is disturbed in the zone of innervation of the affected segments. With damage to the diameter of the spinal cord, taking acetylsalicylic acid causes sweating only above the site of the lesion.

Trial with pilocarpine. The patient is injected subcutaneously with 1 ml of a 1% solution of pilocarpine hydrochloride. As a result of irritation of the postganglionic fibers going to the sweat glands, sweating increases.

It should be borne in mind that pilocarpine excites peripheral M-cholinergic receptors, which cause increased secretion of the digestive and bronchial glands, constriction of the pupils, an increase in the tone of the smooth muscles of the bronchi, intestines, gall and bladder, uterus, but pilocarpine has the strongest effect on sweating. With damage to the lateral horns of the spinal cord or its anterior roots in the corresponding area of the skin, after taking acetylsalicylic acid, sweating does not occur, and the introduction of pilocarpine causes sweating, since the postganglionic fibers that respond to this drug remain intact.

Light bath. Warming the patient causes sweating. This is a spinal reflex similar to the pilomotor reflex. The defeat of the sympathetic trunk completely eliminates sweating after the use of pilocarpine, acetylsalicylic acid and warming the body.

Skin thermometry. Skin temperature is examined using electrothermometers. Skin temperature reflects the state of skin blood supply, which is an important indicator of autonomic innervation. Areas of hyper-, normo- and hypothermia are determined. The difference in skin temperature of 0.5 °C in symmetrical areas indicates a violation of autonomic innervation.

Electroencephalography is used to study the autonomic nervous system. The method makes it possible to judge the functional state of the synchronizing and desynchronizing systems of the brain during the transition from wakefulness to sleep.

There is a close relationship between the autonomic nervous system and the emotional state of a person, therefore, the psychological status of the subject is studied. To do this, use special sets of psychological tests, the method of experimental psychological testing.

6.7. Clinical manifestations of lesions of the autonomic nervous system

With dysfunction of the autonomic nervous system, various disorders occur. Violations of its regulatory functions are periodic and paroxysmal. Most pathological processes do not lead to the loss of certain functions, but to irritation, i.e. to increased excitability of central and peripheral structures. On the-

disruption in some parts of the autonomic nervous system can spread to others (repercussion). The nature and severity of symptoms are largely determined by the level of damage to the autonomic nervous system.

Damage to the cerebral cortex, especially the limbic-reticular complex, can lead to the development of vegetative, trophic, and emotional disorders. They can be caused by infectious diseases, injuries of the nervous system, intoxication. Patients become irritable, quick-tempered, quickly exhausted, they have hyperhidrosis, instability of vascular reactions, fluctuations in blood pressure, pulse. Irritation of the limbic system leads to the development of paroxysms of pronounced vegetative-visceral disorders (cardiac, gastrointestinal, etc.). Psychovegetative disorders are observed, including emotional disorders (anxiety, anxiety, depression, asthenia) and generalized autonomic reactions.

If the hypothalamic region is affected (Fig. 6.7) (tumor, inflammatory processes, circulatory disorders, intoxication, trauma), vegetative-trophic disorders may occur: sleep and wakefulness rhythm disturbances, thermoregulation disorder (hyper- and hypothermia), ulceration in the gastric mucosa, lower part of the esophagus, acute perforation of the esophagus, duodenum and stomach, as well as endocrine disorders: diabetes insipidus, adiposogenital obesity, impotence.

Damage to the vegetative formations of the spinal cord with segmental disorders and disorders localized below the level of the pathological process

Patients may have vasomotor disorders (hypotension), sweating disorders and pelvic functions. With segmental disorders, trophic changes are noted in the relevant areas: increased dryness of the skin, local hypertrichosis or local hair loss, trophic ulcers and osteoarthropathy.

With the defeat of the nodes of the sympathetic trunk, similar clinical manifestations occur, especially pronounced with the involvement of the cervical nodes. There is a violation of sweating and a disorder of pilomotor reactions, hyperemia and an increase in the temperature of the skin of the face and neck; due to a decrease in the tone of the muscles of the larynx, hoarseness of the voice and even complete aphonia may occur; Bernard-Horner syndrome.

Rice. 6.7.

1 - damage to the lateral zone (increased drowsiness, chills, increased pilomotor reflexes, pupillary constriction, hypothermia, low blood pressure); 2 - damage to the central zone (violation of thermoregulation, hyperthermia); 3 - damage to the supraoptic nucleus (impaired secretion of antidiuretic hormone, diabetes insipidus); 4 - damage to the central nuclei (pulmonary edema and erosion of the stomach); 5 - damage to the paraventricular nucleus (adipsia); 6 - damage to the anteromedial zone (increased appetite and impaired behavioral responses)

The defeat of the peripheral parts of the autonomic nervous system is accompanied by a number of characteristic symptoms. Most often there is a kind of pain syndrome - sympathalgia. The pains are burning, pressing, bursting, tend to gradually spread beyond the area of primary localization. Pain is provoked and aggravated by changes in barometric pressure and ambient temperature. Changes in the color of the skin due to spasm or expansion of peripheral vessels are possible: blanching, redness or cyanosis, changes in sweating and skin temperature.

Autonomic disorders can occur with damage to the cranial nerves (especially the trigeminal), as well as the median, sciatic, etc. The defeat of the autonomic ganglia of the face and oral cavity causes burning pain in the area of innervation related to this ganglion, paroxysm, hyperemia, increased sweating, in case lesions of the submandibular and sublingual nodes - an increase in salivation.

Chapter 17

Antihypertensives are drugs that lower blood pressure. Most often they are used for arterial hypertension, i.e. with high blood pressure. Therefore, this group of substances is also called antihypertensive agents.

Arterial hypertension is a symptom of many diseases. There are primary arterial hypertension, or hypertension (essential hypertension), as well as secondary (symptomatic) hypertension, for example, arterial hypertension with glomerulonephritis and nephrotic syndrome (renal hypertension), with narrowing of the renal arteries (renovascular hypertension), pheochromocytoma, hyperaldosteronism, etc.

In all cases, seek to cure the underlying disease. But even if this fails, arterial hypertension should be eliminated, since arterial hypertension contributes to the development of atherosclerosis, angina pectoris, myocardial infarction, heart failure, visual impairment, and impaired renal function. A sharp increase in blood pressure - a hypertensive crisis can lead to bleeding in the brain (hemorrhagic stroke).

In different diseases, the causes of arterial hypertension are different. In the initial stage of hypertension, arterial hypertension is associated with an increase in the tone of the sympathetic nervous system, which leads to an increase in cardiac output and narrowing of blood vessels. In this case, blood pressure is effectively reduced by substances that reduce the influence of the sympathetic nervous system (hypotensive agents of central action, adrenoblockers).

In kidney diseases, in the late stages of hypertension, an increase in blood pressure is associated with activation of the renin-angiotensin system. The resulting angiotensin II constricts blood vessels, stimulates the sympathetic system, increases the release of aldosterone, which increases the reabsorption of Na + ions in the renal tubules and thus retains sodium in the body. Drugs that reduce the activity of the renin-angiotensin system should be prescribed.

In pheochromocytoma (a tumor of the adrenal medulla), the adrenaline and norepinephrine secreted by the tumor stimulate the heart, constrict the blood vessels. The pheochromocytoma is removed surgically, but before the operation, during the operation, or, if the operation is not possible, lower the blood pressure with the help of wasp-adrenergic blockers.

A frequent cause of arterial hypertension may be a delay in the body of sodium due to excessive consumption of table salt and insufficiency of natriuretic factors. An increased content of Na + in the smooth muscles of blood vessels leads to vasoconstriction (the function of the Na + / Ca 2+ exchanger is disturbed: the entry of Na + and the release of Ca 2+ decrease; the level of Ca 2+ in the cytoplasm of smooth muscles increases). As a result, blood pressure rises. Therefore, in arterial hypertension, diuretics are often used that can remove excess sodium from the body.

In arterial hypertension of any genesis, myotropic vasodilators have an antihypertensive effect.

It is believed that in patients with arterial hypertension, antihypertensive drugs should be used systematically, preventing an increase in blood pressure. For this, it is advisable to prescribe long-acting antihypertensive drugs. Most often, drugs are used that act 24 hours and can be administered once a day (atenolol, amlodipine, enalapril, losartan, moxonidine).

In practical medicine, among antihypertensive drugs, diuretics, β-blockers, calcium channel blockers, α-blockers, ACE inhibitors, and AT 1 receptor blockers are most often used.

To stop hypertensive crises, diazoxide, clonidine, azamethonium, labetalol, sodium nitroprusside, nitroglycerin are administered intravenously. In non-severe hypertensive crises, captopril and clonidine are prescribed sublingually.

Classification of antihypertensive drugs

I. Drugs that reduce the influence of the sympathetic nervous system (neurotropic antihypertensive drugs):

1) means of central action,

2) means blocking sympathetic innervation.

P. Myotropic vasodilators:

1) donors N0,

2) potassium channel activators,

3) drugs with an unknown mechanism of action.

III. Calcium channel blockers.

IV. Means that reduce the effects of the renin-angiotensin system:

1) drugs that disrupt the formation of angiotensin II (drugs that reduce renin secretion, ACE inhibitors, vasopeptidase inhibitors),

2) blockers of AT 1 receptors.

V. Diuretics.

Drugs that reduce the effects of the sympathetic nervous system

(neurotropic antihypertensive drugs)

The higher centers of the sympathetic nervous system are located in the hypothalamus. From here, excitation is transmitted to the center of the sympathetic nervous system, located in the rostroventrolateral region of the medulla oblongata (RVLM - rostro-ventrolateral medulla), traditionally called the vasomotor center. From this center, impulses are transmitted to the sympathetic centers of the spinal cord and further along the sympathetic innervation to the heart and blood vessels. Activation of this center leads to an increase in the frequency and strength of heart contractions (increase in cardiac output) and to an increase in the tone of blood vessels - blood pressure rises.

It is possible to reduce blood pressure by inhibiting the centers of the sympathetic nervous system or by blocking the sympathetic innervation. In accordance with this, neurotropic antihypertensive drugs are divided into central and peripheral agents.

TO centrally acting antihypertensives include clonidine, moxonidine, guanfacine, methyldopa.

Clonidine (clophelin, hemiton) - a 2 -adrenomimetic, stimulates a 2A -adrenergic receptors in the center of the baroreceptor reflex in the medulla oblongata (nuclei of the solitary tract). In this case, the centers of the vagus (nucleus ambiguus) and inhibitory neurons are excited, which have a depressing effect on the RVLM (vasomotor center). In addition, the inhibitory effect of clonidine on RVLM is due to the fact that clonidine stimulates I 1 -receptors (imidazoline receptors).

As a result, the inhibitory effect of the vagus on the heart increases and the stimulating effect of sympathetic innervation on the heart and blood vessels decreases. As a result, cardiac output and the tone of blood vessels (arterial and venous) decrease - blood pressure decreases.

In part, the hypotensive effect of clonidine is associated with the activation of presynaptic a 2 -adrenergic receptors at the ends of sympathetic adrenergic fibers - the release of norepinephrine decreases.

At higher doses, clonidine stimulates extrasynaptic a 2 B -adrenergic receptors of the smooth muscles of blood vessels (Fig. 45) and, with rapid intravenous administration, can cause short-term vasoconstriction and an increase in blood pressure (therefore, intravenous clonidine is administered slowly, over 5-7 minutes).

In connection with the activation of a 2 -adrenergic receptors of the central nervous system, clonidine has a pronounced sedative effect, potentiates the action of ethanol, and exhibits analgesic properties.

Clonidine is a highly active antihypertensive agent (therapeutic dose when administered orally 0.000075 g); acts for about 12 hours. However, with systematic use, it can cause a subjectively unpleasant sedative effect (absent-mindedness, inability to concentrate), depression, decreased tolerance to alcohol, bradycardia, dry eyes, xerostomia (dry mouth), constipation, impotence. With a sharp cessation of taking the drug, a pronounced withdrawal syndrome develops: after 18-25 hours, blood pressure rises, a hypertensive crisis is possible. β-Adrenergic blockers increase the clonidine withdrawal syndrome, so these drugs are not prescribed together.

Clonidine is mainly used to quickly lower blood pressure in hypertensive crises. In this case, clonidine is administered intravenously over 5-7 minutes; with rapid administration, an increase in blood pressure is possible due to stimulation of a 2 -adrenergic receptors of blood vessels.

Clonidine solutions in the form of eye drops are used in the treatment of glaucoma (reduces the production of intraocular fluid).

Moxonidine(cint) stimulates imidazoline 1 1 receptors in the medulla oblongata and, to a lesser extent, a 2 adrenoreceptors. As a result, the activity of the vasomotor center decreases, cardiac output and the tone of blood vessels decrease - blood pressure decreases.

The drug is prescribed orally for the systematic treatment of arterial hypertension 1 time per day. Unlike clonidine, when using moxonidine, sedation, dry mouth, constipation, and withdrawal syndrome are less pronounced.

Guanfacine(Estulik) similarly to clonidine stimulates central a 2 -adrenergic receptors. Unlike clonidine, it does not affect 1 1 receptors. The duration of the hypotensive effect is about 24 hours. Assign inside for the systematic treatment of arterial hypertension. The withdrawal syndrome is less pronounced than that of clonidine.

Methyldopa(dopegit, aldomet) according to the chemical structure - a-methyl-DOPA. The drug is prescribed inside. In the body, methyldopa is converted to methylnorepinephrine, and then to methyladrenaline, which stimulate the a 2 -adrenergic receptors of the center of the baroreceptor reflex.

Metabolism of methyldopa

The hypotensive effect of the drug develops after 3-4 hours and lasts about 24 hours.

Side effects of methyldopa: dizziness, sedation, depression, nasal congestion, bradycardia, dry mouth, nausea, constipation, liver dysfunction, leukopenia, thrombocytopenia. In connection with the blocking effect of a-methyl-dopamine on dopaminergic transmission, the following are possible: parkinsonism, increased production of prolactin, galactorrhea, amenorrhea, impotence (prolactin inhibits the production of gonadotropic hormones). With a sharp discontinuation of the drug, the withdrawal syndrome manifests itself after 48 hours.

Drugs that block peripheral sympathetic innervation.

To reduce blood pressure, sympathetic innervation can be blocked at the level of: 1) sympathetic ganglia, 2) endings of postganglionic sympathetic (adrenergic) fibers, 3) adrenoreceptors of the heart and blood vessels. Accordingly, ganglioblockers, sympatholytics, adrenoblockers are used.

Ganglioblockers - hexamethonium benzosulfonate(benzo-hexonium), azamethonium(pentamine), trimetaphan(Arfonad) block the transmission of excitation in the sympathetic ganglia (block N N -xo-linoreceptors of ganglionic neurons), block N N -cholinergic receptors of the chromaffin cells of the adrenal medulla and reduce the release of adrenaline and norepinephrine. Thus, ganglion blockers reduce the stimulating effect of sympathetic innervation and catecholamines on the heart and blood vessels. There is a weakening of the contractions of the heart and the expansion of arterial and venous vessels - arterial and venous pressure decreases. At the same time, ganglion blockers block the parasympathetic ganglia; thus eliminate the inhibitory effect of the vagus nerves on the heart and usually cause tachycardia.

Ganglioblockers are of little use for systematic use due to side effects (severe orthostatic hypotension, disturbance of accommodation, dry mouth, tachycardia; bowel and bladder atony, sexual dysfunction are possible).

Hexamethonium and azamethonium act for 2.5-3 hours; administered intramuscularly or under the skin in hypertensive crises. Azamethonium is also administered intravenously slowly in 20 ml of isotonic sodium chloride solution in case of a hypertensive crisis, swelling of the brain, lungs against the background of high blood pressure, with spasms of peripheral vessels, with intestinal, hepatic or renal colic.

Trimetafan acts 10-15 minutes; is administered in solutions intravenously by drip for controlled hypotension during surgical operations.

Sympatholytics- reserpine, guanethidine(octadin) reduce the release of norepinephrine from the endings of sympathetic fibers and thus reduce the stimulating effect of sympathetic innervation on the heart and blood vessels - arterial and venous pressure decreases. Reserpine reduces the content of norepinephrine, dopamine and serotonin in the central nervous system, as well as the content of adrenaline and norepinephrine in the adrenal glands. Guanethidine does not penetrate the blood-brain barrier and does not change the content of catecholamines in the adrenal glands.

Both drugs differ in the duration of action: after the systematic administration is stopped, the hypotensive effect can persist for up to 2 weeks. Guanethidine is much more effective than reserpine, but due to severe side effects, it is rarely used.

In connection with the selective blockade of sympathetic innervation, the influences of the parasympathetic nervous system predominate. Therefore, when using sympatholytics, the following are possible: bradycardia, increased secretion of HC1 (contraindicated in peptic ulcer), diarrhea. Guanethidine causes significant orthostatic hypotension (associated with a decrease in venous pressure); when using reserpine, orthostatic hypotension is not very pronounced. Reserpine reduces the level of monoamines in the central nervous system, can cause sedation, depression.

but -Ldrenoblockers reduce the ability to stimulate the effect of sympathetic innervation on blood vessels (arteries and veins). In connection with the expansion of blood vessels, arterial and venous pressure decreases; heart contractions reflexively increase.

a 1 - Adrenoblockers - prazosin(minipress), doxazosin, terazosin administered orally for the systematic treatment of arterial hypertension. Prazosin acts 10-12 hours, doxazosin and terazosin - 18-24 hours.

Side effects of a 1 -blockers: dizziness, nasal congestion, moderate orthostatic hypotension, tachycardia, frequent urination.

a 1 a 2 - Adrenoblocker phentolamine used for pheochromocytoma before surgery and during surgery to remove pheochromocytoma, as well as in cases where surgery is not possible.

β -Adrenoblockers- one of the most commonly used groups of antihypertensive drugs. With systematic use, they cause a persistent hypotensive effect, prevent sharp rises in blood pressure, practically do not cause orthostatic hypotension, and, in addition to hypotensive properties, have antianginal and antiarrhythmic properties.

β-blockers weaken and slow down the contractions of the heart - systolic blood pressure decreases. At the same time, β-blockers constrict blood vessels (block β 2 -adrenergic receptors). Therefore, with a single use of β-blockers, mean arterial pressure usually decreases slightly (in isolated systolic hypertension, blood pressure may decrease after a single use of β-blockers).

However, if p-blockers are used systematically, then after 1-2 weeks, vasoconstriction is replaced by their expansion - blood pressure decreases. Vasodilation is explained by the fact that with the systematic use of β-blockers, due to a decrease in cardiac output, the baroreceptor depressor reflex is restored, which is weakened in arterial hypertension. In addition, vasodilation is facilitated by a decrease in renin secretion by juxtaglomerular cells of the kidneys (block of β 1 -adrenergic receptors), as well as blockade of presynaptic β 2 -adrenergic receptors at the endings of adrenergic fibers and a decrease in the release of norepinephrine.

For the systematic treatment of arterial hypertension, long-acting β 1 -adrenergic blockers are more often used - atenolol(tenormin; lasts about 24 hours), betaxolol(valid up to 36 hours).

Side effects of β-blockers: bradycardia, heart failure, difficulty in atrioventricular conduction, a decrease in the level of HDL in blood plasma, an increase in the tone of the bronchi and peripheral vessels (less pronounced in β 1 -blockers), an increase in the action of hypoglycemic agents, a decrease in physical activity.

a 2 β -Adrenoblockers - labetalol(transat), carvedilol(dilatrend) reduce cardiac output (block of p-adrenergic receptors) and reduce the tone of peripheral vessels (block of a-adrenergic receptors). The drugs are used orally for the systematic treatment of arterial hypertension. Labetalol is also administered intravenously in hypertensive crises.

Carvedilol is also used in chronic heart failure.

Content

Parts of the autonomic system are the sympathetic and parasympathetic nervous systems, the latter having a direct impact and closely related to the work of the heart muscle, the frequency of myocardial contraction. It is localized partially in the brain and spinal cord. The parasympathetic system provides relaxation and recovery of the body after physical, emotional stress, but cannot exist separately from the sympathetic department.

What is the parasympathetic nervous system

The department is responsible for the functionality of the organism without its participation. For example, parasympathetic fibers provide respiratory function, regulate the heartbeat, dilate blood vessels, control the natural process of digestion and protective functions, and provide other important mechanisms. The parasympathetic system is necessary for a person to relax the body after exercise. With its participation, muscle tone decreases, the pulse returns to normal, the pupil and vascular walls narrow. This happens without human intervention - arbitrarily, at the level of reflexes

The main centers of this autonomous structure are the brain and spinal cord, where nerve fibers are concentrated, providing the fastest possible transmission of impulses for the operation of internal organs and systems. With their help, you can control blood pressure, vascular permeability, cardiac activity, internal secretion of individual glands. Each nerve impulse is responsible for a certain part of the body, which, when excited, begins to react.

It all depends on the localization of the characteristic plexuses: if the nerve fibers are in the pelvic area, they are responsible for physical activity, and in the digestive system organs - for the secretion of gastric juice, intestinal motility. The structure of the autonomic nervous system has the following constructive sections with unique functions for the whole organism. This:

pituitary;
hypothalamus;
nervus vagus;
epiphysis

This is how the main elements of the parasympathetic centers are designated, and the following are considered additional structures:

nerve nuclei of the occipital zone;
sacral nuclei;
cardiac plexuses to provide myocardial shocks;
hypogastric plexus;
lumbar, celiac and thoracic nerve plexuses.

Sympathetic and parasympathetic nervous system

Comparing the two departments, the main difference is obvious. The sympathetic department is responsible for activity, reacts in moments of stress, emotional arousal. As for the parasympathetic nervous system, it "connects" in the stage of physical and emotional relaxation. Another difference is the mediators that carry out the transition of nerve impulses in synapses: in sympathetic nerve endings it is norepinephrine, in parasympathetic nerve endings it is acetylcholine.

Features of interaction between departments

The parasympathetic division of the autonomic nervous system is responsible for the smooth operation of the cardiovascular, genitourinary and digestive systems, while parasympathetic innervation of the liver, thyroid gland, kidneys, and pancreas takes place. The functions are different, but the impact on the organic resource is complex. If the sympathetic department provides excitation of the internal organs, then the parasympathetic department helps to restore the general condition of the body. If there is an imbalance of the two systems, the patient needs treatment.

Where are the centers of the parasympathetic nervous system located?

The sympathetic nervous system is structurally represented by the sympathetic trunk in two rows of nodes on both sides of the spine. Externally, the structure is represented by a chain of nerve lumps. If we touch on the element of so-called relaxation, the parasympathetic part of the autonomic nervous system is localized in the spinal cord and brain. So, from the central sections of the brain, the impulses that arise in the nuclei go as part of the cranial nerves, from the sacral sections - as part of the pelvic splanchnic nerves, reach the organs of the small pelvis.

Functions of the parasympathetic nervous system

Parasympathetic nerves are responsible for the body's natural recovery, normal myocardial contraction, muscle tone, and productive smooth muscle relaxation. Parasympathetic fibers differ in local action, but in the end they act together - plexuses. With a local lesion of one of the centers, the autonomic nervous system as a whole suffers. The effect on the body is complex, and doctors distinguish the following useful functions:

relaxation of the oculomotor nerve, pupil constriction;
normalization of blood circulation, systemic blood flow;
restoration of habitual breathing, narrowing of the bronchi;
lowering blood pressure;
control of an important indicator of blood glucose;
reduction in heart rate;
slowing down the passage of nerve impulses;
decrease in eye pressure;
regulation of the glands of the digestive system.

In addition, the parasympathetic system helps the vessels of the brain and genital organs to expand, and the smooth muscles to tone up. With its help, a natural cleansing of the body occurs due to such phenomena as sneezing, coughing, vomiting, going to the toilet. In addition, if symptoms of arterial hypertension begin to appear, it is important to understand that the above-described nervous system is responsible for cardiac activity. If one of the structures - sympathetic or parasympathetic - fails, measures must be taken, since they are closely related.

Diseases

Before using certain medications, doing research, it is important to correctly diagnose diseases associated with impaired functioning of the parasympathetic structure of the brain and spinal cord. A health problem manifests itself spontaneously, it can affect internal organs, affect habitual reflexes. The following violations of the body of any age may be the basis:

Cyclic paralysis. The disease is provoked by cyclic spasms, severe damage to the oculomotor nerve. The disease occurs in patients of different ages, accompanied by degeneration of the nerves.
Syndrome of the oculomotor nerve. In such a difficult situation, the pupil can expand without exposure to a stream of light, which is preceded by damage to the afferent section of the pupillary reflex arc.
Block nerve syndrome. A characteristic ailment is manifested in the patient by a slight strabismus, imperceptible to the average layman, while the eyeball is directed inward or upward.
Injured abducens nerves. In the pathological process, strabismus, double vision, pronounced Fauville's syndrome are simultaneously combined in one clinical picture. Pathology affects not only the eyes, but also the facial nerves.
Trigeminal nerve syndrome. Among the main causes of pathology, doctors distinguish an increased activity of pathogenic infections, a violation of systemic blood flow, damage to the cortical-nuclear pathways, malignant tumors, and traumatic brain injury.
Syndrome of the facial nerve. There is an obvious distortion of the face, when a person arbitrarily has to smile, while experiencing pain. More often it is a complication of the disease.

VNS consists of :

sympathetic

parasympathetic divisions.

Both departments innervate most of the internal organs and often have the opposite effect.

VNS centers located in the middle, medulla oblongata and spinal cord.

IN reflex arc In the autonomic part of the nervous system, an impulse from the center is transmitted through two neurons.

Consequently, simple autonomic reflex arc represented by three neurons:

the first link in the reflex arc is sensory neuron, whose receptor originates in organs and tissues

the second link of the reflex arc carries impulses from the spinal cord or brain to the working organ. This pathway of the autonomic reflex arc is represented by two neurons. First of these neurons is located in the autonomic nuclei of the nervous system. Second neuron- This is a motor neuron, the body of which lies in the peripheral nodes of the autonomic nervous. The processes of this neuron are sent to organs and tissues as part of organ autonomic or mixed nerves. The third neurons terminate on smooth muscles, glands and other tissues.

Sympathetic nuclei are located in the lateral horns of the spinal cord at the level of all thoracic and three upper lumbar segments.

Nuclei of the parasympathetic nervous system located in the middle, medulla oblongata and in the sacral spinal cord.

The transmission of nerve impulses takes place in synapses where the mediators of the sympathetic system are, most often, adrenalin And acetylcholine, and the parasympathetic system - acetylcholine.

Most organs innervated by both sympathetic and parasympathetic fibers. However, blood vessels, sweat glands, and the adrenal medulla are only innervated by sympathetic nerves.

parasympathetic nerve impulses weaken cardiac activity, dilate blood vessels, reduce blood pressure, reduce blood glucose levels.

accelerates and enhances the work of the heart, increases blood pressure, constricts blood vessels, slows down the digestive system.

autonomic nervous system does not have its own sensitive ways. They are common to the somatic and autonomic nervous systems.

Important in the regulation of the activity of internal organs is the vagus nerve, which extends from the medulla oblongata and provides parasympathetic innervation of the organs of the neck, chest and abdominal cavities. Impulses along this nerve slow down the work of the heart, dilate the blood vessels, increase the secretion of the digestive glands, and so on.

Properties	sympathetic	Parasympathetic
Origin of nerve fibers	They come out of the cranial, thoracic and lumbar regions of the central nervous system.	They come out of the cranial and sacral parts of the central nervous system.
Location of the ganglia	Near the spinal cord.	next to the effector.
Fiber length	Short preganglionic and long postganglionic fibers.	Long preganglionic and short postganglionic fibers.
Number of fibers	Numerous postganglionic fibers	Few postganglionic fibers
Fiber distribution	Preganglionic fibers innervate large areas	Preganglionic fibers innervate limited areas
Zone of influence	Action generalized	The action is local
Mediator	Norepinephrine	Acetylcholine
General Effects	Increases the intensity of the exchange	Reduces the intensity of metabolism or does not affect it
	Enhances rhythmic forms of activity	Reduces rhythmic forms of activity
	Reduces sensitivity thresholds	Restores sensitivity thresholds to normal levels
Total effect	Exciting	braking
Under what conditions is it activated?	Dominant during times of danger, stress and activity	Dominates at rest, controls normal physiological functions

The nature of the interaction between the sympathetic and parasympathetic divisions of the nervous system

1. Each of the departments of the autonomic nervous system can have an excitatory or inhibitory effect on one or another organ: under the influence of sympathetic nerves, the heartbeat quickens, but the intensity of intestinal motility decreases. Under the influence of the parasympathetic division, the heart rate decreases, but the activity of the digestive glands increases.

2. If any organ is innervated by both parts of the autonomic nervous system, then their action is usually just the opposite: the sympathetic department strengthens the contractions of the heart, and the parasympathetic weakens; parasympathetic increases pancreatic secretion, and sympathetic decreases. But there are exceptions: the secretory nerves for the salivary glands are parasympathetic, while the sympathetic nerves do not inhibit salivation, but cause the release of a small amount of thick viscous saliva.

3. Some organs are predominantly either sympathetic or parasympathetic nerves: sympathetic nerves approach the kidneys, spleen, sweat glands, and predominantly parasympathetic nerves approach the bladder.

4. The activity of some organs is controlled by only one section of the nervous system - sympathetic: when the sympathetic section is activated, sweating increases, and when the parasympathetic section is activated, it does not change, the sympathetic fibers increase the contraction of the smooth muscles that raise the hair, and the parasympathetic ones do not change. Under the influence of the sympathetic department of the nervous system, the activity of some processes and functions can change: blood clotting is accelerated, metabolism is more intense, and mental activity is increased.

Reactions of the sympathetic nervous system

Sympathetic nervous system depending on the nature and strength of the stimuli, it answers either simultaneous activation all its departments, or reflex answers of separate parts. Simultaneous activation of the entire sympathetic nervous system is observed most often when the hypothalamus is activated (fear, fear, unbearable pain). The result of this extensive reaction, which involves the entire body, is the stress response. In other cases, certain parts of the sympathetic nervous system are activated reflexively and with the involvement of the spinal cord.

Simultaneous activation of most parts of the sympathetic system helps the body to produce an unusually large amount of muscle work. This is facilitated by an increase in blood pressure, blood flow in working muscles (with a simultaneous decrease in blood flow in the gastrointestinal tract and kidneys), an increase in metabolic rate, glucose concentration in blood plasma, glycogen breakdown in the liver and muscles, muscle strength, mental performance, blood clotting rate. . The sympathetic nervous system is strongly excited in many emotional states. In a state of rage, the hypothalamus is stimulated. Signals are transmitted through the reticular formation of the brain stem to the spinal cord and cause a massive sympathetic discharge; all of the above reactions turn on immediately. This reaction is called the sympathetic anxiety reaction, or the fight or flight reaction, because an instant decision is required - to stay and fight or flee.

Examples of reflexes of the sympathetic department nervous system are:

- expansion of blood vessels with local muscle contraction;
- sweating when a local area of the skin is heated.

A modified sympathetic ganglion is the adrenal medulla. It produces the hormones epinephrine and norepinephrine, the points of application of which are the same target organs as for the sympathetic department of the nervous system. The action of the hormones of the adrenal medulla is more pronounced than that of the sympathetic division.

Reactions of the parasympathetic system

parasympathetic system carries out local and more specific control of the functions of effector (executive) organs. For example, parasympathetic cardiovascular reflexes usually act only on the heart, increasing or decreasing its rate of contraction. Other parasympathetic reflexes act in the same way, causing, for example, salivation or the secretion of gastric juice. The rectal emptying reflex does not cause any changes in a significant part of the colon.

Differences in the influence of the sympathetic and parasympathetic divisions of the autonomic nervous system due to the characteristics of their organization. Sympathetic postganglionic neurons have an extensive zone of innervation, and therefore their excitation usually leads to generalized (broad action) reactions. The overall effect of the influence of the sympathetic department is to inhibit the activity of most internal organs and stimulate the heart and skeletal muscles, i.e. in the preparation of the body for the behavior of the "fight" or "flight" type. Parasympathetic postganglionic neurons are located in the organs themselves, innervate limited areas, and therefore have a local regulatory effect. In general, the function of the parasympathetic division is to regulate processes that ensure the restoration of body functions after vigorous activity.

Influence of sympathetic and parasympathetic nerves on various organs

Authority or system	Influence
Authority or system	parasympathetic parts	sympathetic parts
Vessels of the brain		Extension
		Extension
Salivary glands	Increased secretion	Decreased secretion
Peripheral arterial vessels		Extension
		Extension
Heart contractions	slowdown	Acceleration and Boost
sweating	Decrease	Gain
Gastrointestinal tract	Increased motor activity	Weakening of motor activity
Adrenal	Decreased secretion of hormones	Increased secretion of hormones
Bladder	Reduction	Relaxation