According to the morphofunctional classification, the nervous system is divided into: somatic And vegetative.

Somatic nervous system ensures the perception of irritations and the implementation of motor reactions of the body as a whole with the participation of skeletal muscles.

Autonomic nervous system (ANS) innervates all internal organs (cardiovascular system, digestion, respiration, genitals, secretions, etc.), smooth muscles of hollow organs, regulates metabolic processes, growth and reproduction

Autonomic (autonomic) nervous system regulates body functions regardless of human will.

The parasympathetic nervous system is the peripheral part of the autonomic nervous system, responsible for maintaining a constant internal environment of the body.

The parasympathetic nervous system consists of:

From the cranial region, in which preganglionic fibers leave the midbrain and rhombencephalon as part of several cranial nerves; And

From the sacral region, in which preganglionic fibers exit the spinal cord as part of its ventral roots.

The parasympathetic nervous system is inhibited the work of the heart, dilates some blood vessels.

The sympathetic nervous system is a peripheral part of the autonomic nervous system, which ensures the mobilization of the body's resources to perform urgent work.

The sympathetic nervous system stimulates the heart, constricts blood vessels and enhances the performance of skeletal muscles.

The sympathetic nervous system is represented by:

Gray matter of the lateral horns of the spinal cord;

Two symmetrical sympathetic trunks with their ganglia;

Internodal and connecting branches; and

Branches and ganglia involved in the formation of nerve plexuses.

The entire autonomic nervous system consists of: parasympathetic And sympathetic departments. Both of these departments innervate the same organs, often having opposite effects on them.

The endings of the parasympathetic division of the autonomic nervous system release the mediator acetylcholine.

Parasympathetic division of the autonomic nervous system regulates the functioning of internal organs under resting conditions. Its activation helps to reduce the frequency and strength of heart contractions, lower blood pressure, and increase both motor and secretory activity of the digestive tract.

The endings of sympathetic fibers secrete norepinephrine and adrenaline as mediators.

Sympathetic division of the autonomic nervous system increases its activity if necessarymobilization of the body's resources. The frequency and strength of heart contractions increases, the lumen of blood vessels narrows, blood pressure rises, and the motor and secretory activity of the digestive system is inhibited.

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

1. Each of the departments of the autonomic nervous system can have an exciting or inhibitory effect on one or another organ. For example, under the influence of sympathetic nerves, the heart rate increases, but the intensity of intestinal motility decreases. Under the influence of the parasympathetic department, 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 exactly the opposite. For example, the sympathetic department strengthens the contractions of the heart, and the parasympathetic weakens it; the parasympathetic increases pancreatic secretion, and the sympathetic decreases. But there are exceptions. Thus, 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 approached predominantly by either sympathetic or parasympathetic nerves. For example, sympathetic nerves approach the kidneys, spleen, and sweat glands, while predominantly parasympathetic nerves approach the bladder.

4. The activity of some organs is controlled by only one part of the nervous system - the sympathetic one. For example: when the sympathetic department is activated, sweating increases, but when the parasympathetic department is activated, it does not change; sympathetic fibers increase the contraction of smooth muscles that raise the hair, but parasympathetic fibers do not change. Under the influence of the sympathetic part of the nervous system, the activity of certain processes and functions may change: blood clotting accelerates, metabolism occurs more intensely, and mental activity increases.

Sympathetic Nervous System Responses

The sympathetic nervous system, depending on the nature and strength of stimulation, responds either by simultaneous activation of all its departments, or by reflex responses of individual parts. Simultaneous activation of the entire sympathetic nervous system is most often observed when the hypothalamus is activated (fright, fear, unbearable pain). The result of this broad, body-wide response 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.

The simultaneous activation of most parts of the sympathetic system helps the body produce unusually large amounts 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 the blood plasma, breakdown of glycogen in the liver and muscles, muscle strength, mental performance, blood clotting rate . The sympathetic nervous system is highly aroused in many emotional states. In a state of rage, the hypothalamus is stimulated. Signals are transmitted through the reticular formation of the brainstem to the spinal cord and cause a massive sympathetic discharge; all the above reactions are activated immediately. This reaction is called the sympathetic anxiety response, or the fight or flight response, because. an instant decision is required - to stay and fight or to flee.

Examples of reflexes of the sympathetic nervous system are:

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

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

Parasympathetic system reactions

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

Differences in the influence of the sympathetic and parasympathetic divisions of the autonomic nervous system are due to the peculiarities of their organization. Sympathetic postganglionic neurons have a wide area of innervation, and therefore their excitation usually leads to generalized (wide-ranging) reactions. The general effect of the influence of the sympathetic department is to inhibit the activity of most internal organs and stimulate the cardiac and skeletal muscles, i.e. in preparing the body for behavior such as “fight” or “flight”. 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 department is to regulate processes that ensure the restoration of body functions after vigorous activity.

Nervous regulation of the heart is carried out by sympathetic and parasympathetic impulses. The former increase the frequency, strength of contractions, and blood pressure, while 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 during 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:

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

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

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

The sympathetic system does not always have a unidirectional effect on organs, which is due to the presence of several types of adrenergic receptors in them.

Ultimately, the body's tolerance to physical and mental stress increases, 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 part of the autonomic nervous system is designed to relax the body, recover from exercise, ensure digestion and store energy.
When the vagus nerve is activated:
blood flow to the stomach and intestines increases;
the release of digestive enzymes and bile production increases;
the bronchi narrow (at rest, much oxygen is not required);

the rhythm of contractions slows down, their strength decreases;

arterial tone decreases and

The influence of two systems on the heart
Although sympathetic and parasympathetic stimulation have opposing 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 increases, the stronger the suppressive effect of the parasympathetic department will be - 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 irritation - the law of the initial level.

Until the age of 40, parasympathetic tone predominates, which affects the slowing of the heart rate at rest and its rapid return to normal after exercise.

And then age-related changes begin - the number of adrenergic receptors decreases while the parasympathetic ganglia are preserved. This leads to the following processes:
the excitability of muscle fibers worsens;
the processes of impulse formation are disrupted;

the sensitivity of the vascular wall and myocardium to the action of stress hormones increases.

Under the influence of ischemia, cells become even more responsive to sympathetic impulses and respond to even the slightest signals by spasming the arteries and accelerating 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 zone of destruction in acute coronary circulatory disorders.

What happens when you get excited The heart contains mainly beta 1 adrenergic receptors, some beta 2 and alpha type. Moreover, they are located on the surface of cardiomyocytes, which increases their accessibility to the main transmitter (conductor) of sympathetic impulses - norepinephrine.

Under the influence of receptor activation, the following changes occur:
the excitability of the cells of the sinus node, conduction system, and muscle fibers increases, they even respond to subthreshold signals;
conduction of the electrical impulse is accelerated;
the amplitude of contractions increases;

the number of pulse beats per minute increases.

Parasympathetic cholinergic receptors of type M are also found on the outer membrane of 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 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 ventricular excitability and increases it in the atria;
slows down heart rate;
inhibits the formation and conduction of impulses;
suppresses the contractility of muscle fibers;
reduces myocardial oxygen demand;

prevents spasm of arterial walls and.

Depending on the predominance of the tone of one of the sections of the autonomic nervous system, patients may have an initial increase in sympathetic influences 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 in patients it is possible to identify:
the skin is dry and pale, the extremities are cold;
the pulse is accelerated, an 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 sedatives and adrenergic blockers as the basis of drug therapy.

With vagotonia, the skin is moist, there is a tendency to faint with a sudden change in body position, movements are slow, load 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 transmitter norepinephrine ensure the body’s activity under the influence of stress factors.

When adrenergic receptors are stimulated, blood pressure increases, the pulse accelerates, and the excitability and conductivity of the myocardium increases.

The parasympathetic department and acetylcholine have the opposite direction of influence on the heart; they are responsible for relaxation and accumulation of energy. Normally, these processes successively replace each other, and when nervous regulation is disturbed (sympathicotonia or vagotonia), blood circulation indicators change.

AUTONOMIC NERVOUS SYSTEM

The autonomic (autonomic) nervous system regulates all internal processes of the body: the functions of internal organs and systems, glands, blood and lymph vessels, smooth and partially striated muscles, sensory organs (Fig. 6.1). It ensures 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 adaptation-trophic function - regulation of metabolism in relation to environmental conditions.

The term "autonomic nervous system" reflects the control of 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, like the somatic one, is the neuron, and the main functional unit is the reflex arc. The autonomic nervous system has a 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 characteristics of functional innervation and is determined by their attitude to drugs 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 has an inhibitory effect on the parasympathetic part.

6.1. Sympathetic division of the autonomic nervous system

The central formations are located in the cerebral cortex, hypothalamic nuclei, brain stem, reticular formation, and also in the spinal cord (in the lateral horns). The cortical representation has not been sufficiently elucidated. From the cells of the lateral horns of the spinal cord at levels from C VIII to L V, the peripheral formations of the sympathetic department 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 some of the fibers end. 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 cerebrum; 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 splanchnic nerve; 12a - lower splanchnic nerve; 13 - superior mesenteric plexus; 14 - inferior 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 - detrusor of the bladder (muscle that pushes 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 includes 24 pairs of sympathetic nodes: 3 cervical, 12 thoracic, 5 lumbar, 4 sacral. From the axons of the cells of the upper cervical sympathetic node, 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 thoracic nodes innervate the aorta, lungs, bronchi, and abdominal organs, and the lumbar nodes innervate the pelvic organs.

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 the limbic-reticular complex). There are mesencephalic and bulbar sections in the brain and sacral sections in the spinal cord. The mesencephalic section includes the nuclei of the cranial nerves: III pair - accessory nucleus of Yakubovich (paired, parvocellular), innervating the muscle that constricts the pupil; Perlia's nucleus (unpaired parvocellular) innervates the ciliary muscle involved in accommodation. The bulbar section consists of the superior and inferior salivary nuclei (VII and IX pairs); X pair - vegetative nucleus, innervating the heart, bronchi, gastrointestinal tract,

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

All organs are under the influence of both the sympathetic and parasympathetic parts of the autonomic nervous system, 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 the creation of reserves of energy substrates are created. The sympathetic part modifies these states (i.e., the functional abilities of the organs) in relation to the function performed. Both parts function in close cooperation. Under certain conditions, functional predominance of one part over the other is possible. If the tone of the parasympathetic part predominates, a state of parasympathotonia develops, and the sympathetic part - sympathotonia. Parasympathotonia is characteristic of the sleep state, sympathotonia is characteristic of affective states (fear, anger, etc.).

In clinical conditions, conditions are possible in which the activity of individual organs or systems of the body 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, Quincke's edema, vasomotor rhinitis, motion sickness; sympathotonic - vascular spasm in the form of Raynaud's syndrome, migraine, transient form of hypertension, vascular crises with hypothalamic syndrome, ganglion lesions, panic attacks. The integration of autonomic and somatic functions is carried out by the cerebral cortex, hypothalamus and reticular formation.

6.3. Limbic-reticular complex

All activities of the autonomic nervous system are controlled and regulated by the cortical parts of the nervous system (frontal cortex, parahippocampal and cingulate gyri). 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 - hippocampal gyrus; 12 - hook; 13 - orbital surface of the frontal pole; 14 - hook-shaped beam; 15 - transverse connection of the amygdala; 16 - anterior commissure; 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 formations of the olfactory pathways located at the base of the brain, the septum pellucidum, 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, putamen, amygdala, anterior tubercle of the thalamus, hypothalamus, frenulus nucleus. 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 autonomic manifestations. A pronounced autonomic effect occurs when the anterior parts of the limbic system are irritated, in particular the orbital cortex, amygdala and cingulate gyrus. In this case, changes in salivation, respiratory rate, increased intestinal motility, urination, defecation, etc. appear.

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 realizes the interaction of nervous and endocrine, the integration of somatic and autonomic activity. The hypothalamus has specific and nonspecific nuclei. Specific nuclei produce hormones (vasopressin, oxytocin) and releasing factors that regulate the secretion of hormones by the anterior pituitary gland.

Sympathetic fibers innervating the face, head and neck begin 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 is directed 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 (cellular accumulations) located in the periarterial plexuses of the branches of the external carotid artery, fibers that are not interrupted in the nodes of the sympathetic trunk end. 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 superior 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 directed 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 they approach the spinal nodes, closing the reflex arc.

Parasympathetic fibers are formed by the axons of the stem parasympathetic nuclei and are directed mainly to the five autonomic ganglia of the face, where they are interrupted. A minority of the fibers are directed to the parasympathetic clusters of cells of the periarterial plexuses, where they are also interrupted, and the postganglionic fibers go as part of the cranial nerves or periarterial plexuses. The parasympathetic part also contains afferent fibers that run in the vagus nerve system and are directed to the sensory nuclei of the brain stem. The anterior and middle sections of the hypothalamic region, through sympathetic and parasympathetic conductors, influence the function of 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 (Yakubovich-Edinger-Westphal nucleus); 3 - oculomotor nerve; 4 - nasociliary branch from the optic nerve; 5 - ciliary node; 6 - short ciliary nerves; 7 - sphincter of the pupil; 8 - pupil dilator; 9 - ciliary muscle; 10 - internal carotid artery; 11 - carotid plexus; 12 - deep petrosal nerve; 13 - upper salivary nucleus; 14 - intermediate nerve; 15 - elbow assembly; 16 - greater petrosal 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 - genicular tympanic nerve; 23 - auriculotemporal nerve; 24 - middle meningeal artery; 25 - parotid gland; 26 - ear node; 27 - lesser petrosal nerve; 28 - tympanic plexus; 29 - auditory tube; 30 - single track; 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 - superior cervical sympathetic node; 41 - cells of the lateral horn ThI-ThII; 42 - 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. Parasympathetic fibers are indicated in green, sympathetic in red, and sensory in blue.

The processes of these neurons, forming preganglionic fibers, leave the spinal cord along 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 upper cervical sympathetic plexus. Postganglionic fibers of this node accompany the internal carotid artery, weaving around its wall, penetrate into the cranial cavity, where they connect with the first branch of the trigeminal nerve, penetrate into the orbital cavity and end at the muscle that dilates the pupil (m. dilatator pupillae).

Sympathetic fibers also innervate other structures of the eye: the tarsal muscles that expand the palpebral fissure, the orbital muscle of the eye, as well as some structures of the face - the 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 is sent to the muscle that constricts the pupil (m. sphincter pupillae), and the other part is involved in providing accommodation.

Disturbance of the autonomic innervation of the eye. Damage to the sympathetic formations causes Bernard-Horner syndrome (Fig. 6.4) with constriction of the pupil (miosis), narrowing of the palpebral fissure (ptosis), and retraction of the eyeball (enophthalmos). The development of homolateral anhidrosis, conjunctival hyperemia, and depigmentation of the iris are also possible.

The development of Bernard-Horner syndrome is possible when the lesion is localized at different levels - involving the posterior longitudinal fasciculus, pathways 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 sympathetic fibers are irritated, a syndrome occurs that is the opposite of Bernard-Horner syndrome (Pourfour du Petit) - dilatation of the palpebral fissure and pupil (mydriasis), exophthalmos.

6.6. Autonomic innervation of the bladder

Regulation of bladder activity is carried out by the sympathetic and parasympathetic parts of the autonomic nervous system (Fig. 6.5) and includes urinary retention and bladder emptying. 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 the activity of the detrusor 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

the parasympathetic center at the level of S II -S IV and the micturition center in the pons (Fig. 6.6). Descending efferent signals send signals that relax the external sphincter, suppress sympathetic activity, remove the block of conduction along parasympathetic fibers, and stimulate the parasympathetic center. The consequence of this is 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.

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

Damage to the parasympathetic centers of the sacral region and 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 autonomic centers can lead to the development of an imperative urge to urinate. When the spinal sympathetic center (Th XI - L II) is damaged, 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 autonomic tone and the level of fluctuations relative to the background value. The higher the initial level, the lower the response will be during functional tests. In some cases, even a paradoxical reaction is possible. Ray study

Rice. 6.5.

1 - cerebral cortex; 2 - fibers that provide voluntary control over bladder emptying; 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 fibers); 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 - genital 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 meals, 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 autonomic tone, it is possible to conduct tests with exposure to pharmacological agents or physical factors. Solutions of adrenaline, insulin, mezaton, pilocarpine, atropine, histamine, etc. are used as pharmacological agents.

Cold test. With the patient lying down, heart rate is calculated and blood pressure is measured. After this, the hand of the other hand is immersed in cold water (4 °C) for 1 minute, then the hand is removed from the water and blood pressure and pulse are recorded every minute until it returns to the original level. Normally this happens within 2-3 minutes. If blood pressure increases 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.

Oculocardiac reflex (Danyini-Aschner). When pressing on the eyeballs in healthy people, the heart rate slows down by 6-12 per minute. If the 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 an 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 s, 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 inducing the oculocardiac reflex.

Orthoclinostatic reflex. The patient's heart rate is calculated while lying on his back, and then he is asked to quickly stand up (orthostatic test). When moving from a horizontal to a vertical position, heart rate increases by 12 per minute with an increase in blood pressure by 20 mmHg. Art. When the patient moves to a horizontal position, 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 slowdown of the pulse during a 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 0.1% adrenaline solution after 10 minutes causes pale 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 the sympathetic innervation is increased.

Skin test with adrenaline. A drop of 0.1% adrenaline solution is applied to the site of the skin injection with a needle. In a healthy person, such an area becomes pale with a pink halo around it.

Test with atropine. Subcutaneous injection of 1 ml of 0.1% atropine solution 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 administration 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 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, the blunt end of a pin). The local reaction occurs as an axon reflex. A red stripe appears at the site of irritation, the width of which depends on the state of the autonomic nervous system. With an increase in sympathetic tone, the stripe is white (white dermographism). Wide stripes of red dermographism, a stripe raised above the skin (elevated dermographism), indicate increased tone of the parasympathetic nervous system.

For topical diagnostics, reflex dermographism is used, which is caused by irritation with a sharp object (drawn across the skin with the tip of a needle). A strip with uneven scalloped edges appears. Reflex dermographism is a spinal reflex. It disappears in the corresponding zones of innervation when the dorsal 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 area.

Pupillary reflexes. They determine the direct and friendly reaction of the pupils to light, the reaction to convergence, accommodation and pain (dilation of the pupils when pricking, pinching and other irritations of any part of the body).

Pilomotor reflex caused by pinching or applying a cold object (a test tube with cold water) or a cooling liquid (cotton wool soaked in ether) to the skin of the shoulder girdle or the back of the head. On the same half of the chest, “goose bumps” appear as a result of contraction of smooth hair muscles. The reflex arc 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. If the hypothalamic region is affected, its asymmetry is possible. When the lateral horns or anterior roots of the spinal cord are damaged, sweating is disrupted in the area of innervation of the affected segments. When the diameter of the spinal cord is damaged, taking acetylsalicylic acid causes sweating only above the site of the lesion.

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

It should be borne in mind that pilocarpine excites peripheral M-cholinergic receptors, causing increased secretion of the digestive and bronchial glands, constriction of the pupils, increased tone of the smooth muscles of the bronchi, intestines, gall and bladder, and uterus, but pilocarpine has the most powerful effect on sweating. If the lateral horns of the spinal cord or its anterior roots are damaged in the corresponding area of the skin, sweating does not occur after taking acetylsalicylic acid, and the administration of pilocarpine causes sweating, since the postganglionic fibers that react to this drug remain intact.

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

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

Electroencephalography is used to study the autonomic nervous system. The method allows us 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 connection between the autonomic nervous system and the emotional state of a person, therefore the psychological status of the subject is studied. For this purpose, special sets of psychological tests and the method of experimental psychological testing are used.

6.7. Clinical manifestations of lesions of the autonomic nervous system

When the autonomic nervous system is dysfunctional, a variety of 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 autonomic, trophic, and emotional disorders. They can be caused by infectious diseases, injuries to the nervous system, and intoxications. Patients become irritable, hot-tempered, quickly exhausted, they experience hyperhidrosis, instability of vascular reactions, fluctuations in blood pressure and pulse. Irritation of the limbic system leads to the development of paroxysms of severe vegetative-visceral disorders (cardiac, gastrointestinal, etc.). Psychovegetative disorders are observed, including emotional disorders (anxiety, restlessness, depression, asthenia) and generalized autonomic reactions.

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

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

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

When the nodes of the sympathetic trunk are affected, similar clinical manifestations occur, especially pronounced when the cervical nodes are involved. There is impaired sweating and disorder of pilomotor reactions, hyperemia and increased temperature of the skin of the face and neck; due to decreased tone of the laryngeal muscles, hoarseness and even complete aphonia may occur; Bernard-Horner syndrome.

Rice. 6.7.

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

Damage to the peripheral parts of the autonomic nervous system is accompanied by a number of characteristic symptoms. The most common type of pain syndrome that occurs is sympathalgia. The pain is burning, pressing, bursting, and tends to gradually spread beyond the area of primary localization. Pain is provoked and intensified by changes in barometric pressure and ambient temperature. Changes in skin color are possible due to spasm or dilation of peripheral vessels: paleness, 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. Damage to the autonomic ganglia of the face and oral cavity causes burning pain in the area of innervation related to this ganglion, paroxysmalness, hyperemia, increased sweating, in the case lesions of the submandibular and sublingual nodes - increased salivation.

Chapter 17. Antihypertensive drugs

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 drugs.

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, they strive 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 renal dysfunction. A sharp increase in blood pressure - a hypertensive crisis can lead to bleeding in the brain (hemorrhagic stroke).

The causes of arterial hypertension are different for different diseases. 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 constriction of blood vessels. In this case, blood pressure is effectively reduced by substances that reduce the influence of the sympathetic nervous system (central-acting antihypertensives, adrenergic blockers).

In kidney disease and 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.

With pheochromocytoma (tumor of the adrenal medulla), adrenaline and norepinephrine secreted by the tumor stimulate the heart and constrict blood vessels. Pheochromocytoma is removed surgically, but before surgery, during surgery, or if surgery is not possible, blood pressure is reduced with the help of wasp-blockers.

A common cause of arterial hypertension may be sodium retention in the body 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 impaired: the entry of Na + and the exit of Ca 2+ decreases; the level of Ca 2+ in the cytoplasm of smooth muscles increases). As a result, blood pressure increases. Therefore, for arterial hypertension, diuretics are often used that can remove excess sodium from the body.

For arterial hypertension of any origin, myotropic vasodilators have an antihypertensive effect.

It is believed that patients with arterial hypertension should use antihypertensive drugs systematically to prevent an increase in blood pressure. For this purpose, it is advisable to prescribe long-acting antihypertensive drugs. The most commonly used drugs are those that act for 24 hours and can be prescribed once a day (atenolol, amlodipine, enalapril, losartan, moxonidine).

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

To relieve hypertensive crises, diazoxide, clonidine, azamethonium, labetalol, sodium nitroprusside, and nitroglycerin are administered intravenously. For mild 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) drugs that block sympathetic innervation.

P. Vasodilators of myotropic action:

1) donors N0,

2) activators of potassium channels,

3) drugs with an unclear mechanism of action.

III. Calcium channel blockers.

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

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

2) AT 1 receptor blockers.

V. Diuretics.

Drugs that reduce the influence 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 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 (increased cardiac output) and to an increase in the tone of blood vessels - blood pressure increases.

Blood pressure can be reduced by inhibiting the centers of the sympathetic nervous system or by blocking sympathetic innervation. In accordance with this, neurotropic antihypertensive drugs are divided into central and peripheral agents.

TO centrally acting antihypertensive drugs include clonidine, moxonidine, guanfacine, methyldopa.

Clonidine (clonidine, hemitone) is an α2-adrenergic agonist, stimulates α2A-adrenergic receptors in the center of the baroreceptor reflex in the medulla oblongata (nucleus of the solitary tract). In this case, the vagal centers (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.

Partly, the hypotensive effect of clonidine is associated with the activation of presynaptic α2-adrenergic receptors at the endings of sympathetic adrenergic fibers - the release of norepinephrine decreases.

In higher doses, clonidine stimulates extrasynaptic a 2 B -adrenergic receptors of 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).

Due to the activation of α2-adrenergic receptors in the central nervous system, clonidine has a pronounced sedative effect, potentiates the effect of ethanol, and exhibits analgesic properties.

Clonidine is a highly active antihypertensive drug (therapeutic dose when administered orally 0.000075 g); lasts about 12 hours. However, when used systematically, it can cause a subjectively unpleasant sedative effect (distracted thoughts, inability to concentrate), depression, decreased tolerance to alcohol, bradycardia, dry eyes, xerostomia (dry mouth), constipation, impotence. If you abruptly stop taking the drug, a pronounced withdrawal syndrome develops: after 18-25 hours, blood pressure rises, and a hypertensive crisis is possible. β-Adrenergic blockers increase clonidine withdrawal syndrome, so these drugs are not prescribed together.

Clonidine is used mainly to quickly lower blood pressure during 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 vascular α2-adrenergic receptors.

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 and, to a lesser extent, a 2 adrenergic receptors in the medulla oblongata. As a result, the activity of the vasomotor center decreases, cardiac output and blood vessel tone decrease, and blood pressure decreases.

The drug is prescribed orally for the systematic treatment of arterial hypertension 1 time per day. In contrast to clonidine, moxonidine causes less pronounced sedation, dry mouth, constipation, and withdrawal symptoms.

Guanfatsin(estulik) similarly to clonidine stimulates central α2-adrenergic receptors. Unlike clonidine, it does not affect 1 1 receptors. The duration of the hypotensive effect is about 24 hours. It is prescribed orally for the systematic treatment of arterial hypertension. Withdrawal syndrome is less pronounced than with clonidine.

Methyldopa(dopegite, aldomet) chemical structure - a-methyl-DOPA. The drug is prescribed orally. In the body, methyldopa is converted into methylnorepinephrine, and then into methyladrenaline, which stimulate the α2-adrenergic receptors of the baroreceptor reflex center.

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. Due to 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). If you abruptly stop taking the drug, withdrawal symptoms appear 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) adrenergic receptors of the heart and blood vessels. Accordingly, ganglion blockers, sympatholytics, and adrenergic blockers are used.

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

For systematic use, ganglion blockers are of little use due to side effects (severe orthostatic hypotension, impaired accommodation, dry mouth, tachycardia; possible intestinal and bladder atony, sexual dysfunction).

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

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

Sympatholytics- reserpine, guanethidine(octadine) 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 their duration of action: after stopping systematic use, the hypotensive effect can last up to 2 weeks. Guanethidine is much more effective than reserpine, but is rarely used due to severe side effects.

Due to 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 ulcers), diarrhea. Guanethidine causes significant orthostatic hypotension (associated with a decrease in venous pressure); When using reserpine, orthostatic hypotension is mild. Reserpine reduces the level of monoamines in the central nervous system and can cause sedation and depression.

A -Adrenergic blockers reduce the stimulating effect of sympathetic innervation on blood vessels (arteries and veins). Due to the dilation of blood vessels, arterial and venous pressure decreases; heart contractions reflexively become more frequent.

a 1 -Adrenergic blockers - prazosin(minipress), doxazosin, terazosin prescribed orally for the systematic treatment of arterial hypertension. Prazosin acts for 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 impossible.

β -Adrenergic blockers- one of the most commonly used groups of antihypertensive drugs. When used systematically, they cause a persistent hypotensive effect, prevent sudden increases in blood pressure, practically do not cause orthostatic hypotension, and, in addition to hypotensive properties, have antianginal and antiarrhythmic properties.

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

However, if p-blockers are used systematically, then after 1-2 weeks the narrowing of blood vessels is replaced by their dilation - blood pressure decreases. Vasodilation is explained by the fact that with the systematic use of beta-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 the secretion of renin by the juxtaglomerular cells of the kidneys (block of β 1 -adrenergic receptors), as well as blockade of presynaptic β 2 -adrenergic receptors in the endings of adrenergic fibers and a decrease in the release of norepinephrine.

For the systematic treatment of arterial hypertension, long-acting β 1-blockers are 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, decreased HDL levels in the blood plasma, increased bronchial and peripheral vascular tone (less pronounced with β 1 -blockers), increased effect of hypoglycemic agents, decreased physical activity.

a 2 β -Adrenergic blockers - labetalol(trandate), carvedilol(Dilatrend) reduce cardiac output (block of β-adrenoreceptors) and reduce the tone of peripheral vessels (block of α-adrenoreceptors). The drugs are used orally for the systematic treatment of arterial hypertension. Labetalol is also administered intravenously during hypertensive crises.

Carvedilol is also used for chronic heart failure.

^ Organ, system, function	Sympathetic innervation	Parasympathetic innervation
Eye	Dilates the palpebral fissure and pupil, causing exophthalmos	Narrows the palpebral fissure and pupil, causing enophthalmos
Nasal mucosa	Constricts blood vessels	Dilates blood vessels
Salivary glands	Reduces secretion, thick saliva	Increases secretion, watery saliva
Heart	Increases the frequency and strength of contractions, increases blood pressure, dilates coronary vessels	Reduces the frequency and strength of contractions, lowers blood pressure, narrows coronary vessels
Bronchi	Dilates the bronchi, reduces mucus secretion	Constricts the bronchi, increases mucus secretion
Stomach, intestines, gallbladder	Reduces secretion, weakens peristalsis, causes atony	Increases secretion, enhances peristalsis, causes spasms
Kidneys	Reduces diuresis	Increases diuresis
Bladder	Inhibits the activity of the bladder muscles, increases sphincter tone	Stimulates the activity of the bladder muscles, reduces sphincter tone
Skeletal muscles	Increases tone and metabolism	Reduces tone and metabolism
Leather	Constricts blood vessels, causes pale, dry skin	Dilates blood vessels, causes redness and sweating of the skin
BX	Increases the level of exchange	Reduces exchange rate
Physical and mental activity	Increases indicator values	Reduces indicator values

2 sympathetic division of the autonomic nervous system. Sympathetic and parasympathetic divisions of the autonomic nervous system: what are they? Additional actions of both sections