Internal analyzers analyze and synthesize status information internal environment body and participate in the regulation of work internal organs. The following analyzers are distinguished: 1) pressure in blood vessels and in internal hollow organs ( peripheral department of this analyzer are mechanoreceptors); 2) temperature analyzer; 3) analyzer of the chemistry of the internal environment of the body; 4) analyzer of osmotic pressure of the internal environment. The receptors of these analyzers are located in various organs, vessels, mucous membranes and central nervous system.
Receptors of internal organs 1. Mechanoreceptors - receptors of blood vessels, heart, lungs, gastrointestinal tract and other internal hollow organs. 2. Chemoreceptors - receptors of the aortic and carotid glomeruli, receptors of the mucous membranes of the digestive tract and respiratory organs, receptors of the serous membranes, as well as chemoreceptors of the brain. 3. Osmoreceptors - localized in the aortic and carotid sinuses, in other vessels of the arterial bed, near capillaries, in the liver and other organs. Some osmoreceptors are mechanoreceptors, some are chemoreceptors. 4. Thermoreceptors - localized in the mucous membranes of the digestive tract, respiratory organs, Bladder, serous membranes, in the walls of arteries and veins, in the carotid sinus, as well as in the nuclei of the hypothalamus.
Glucoreceptors Cells that are sensitive to glucose. They are found in the hypothalamus and liver. Glucoreceptors in the hypothalamus function as sensors for blood glucose concentrations; The body uses their signals to regulate food intake. They react most strongly to a decrease in glucose levels.
Baroreceptors (from the Greek baros - heaviness), mechanoreceptors are sensitive nerve endings in blood vessels that perceive changes in blood pressure and reflexively regulate its level; come into a state of excitation when the walls of blood vessels are stretched. Baroreceptors are present in all vessels; their accumulations are concentrated mainly in reflexogenic zones (cardiac, aortic, sinocarotid, pulmonary, etc.). When blood pressure increases, baroreceptors send impulses to the central nervous system that suppress the tone of the vascular center and excite the central formations of the parasympathetic division of the autonomic nervous system, which leads to a decrease in pressure.
Baroreceptor reflex - a reaction to changes in the stretching of the walls of the aortic arch and carotid sinus. Increase blood pressure leads to stretching of baroreceptors, signals from which enter the central nervous system. Then the signals feedback are directed to the centers of the autonomic nervous system, and from them to the vessels. As a result, the pressure drops to normal levels. Another reflex is triggered by excessive stretching of the walls of the atria (if the ventricles do not have time to pump out blood): the work of the heart increases. If the pressure is below normal, it is activated sympathetic system, the heart begins to beat faster and stronger; if the pressure is higher than normal, the vagus nerve is activated, and the heart’s work slows down.
Structural and functional characteristics of baroreceptors and their innervation Location of baroreceptors and chemoreceptors in the aorta and carotid artery Baroreceptors are branched nerve endings located in the wall of the arteries. They are excited when stretched. A number of baroreceptors are present in the wall of almost every major artery in the chest and neck. There are especially many baroreceptors in the wall of the internal carotid artery (carotid sinus) and in the wall of the aortic arch.
Signals from the carotid baroreceptors are carried along the very thin nerves of Hering to the glossopharyngeal nerve in the upper neck, and then along the fasciculus solitarius to the medullary portion of the brainstem. Signals from the aortic baroreceptors located in the aortic arch are also transmitted along the fibers of the vagus nerve to the solitary tract of the medulla oblongata.
1 2 Nervous regulation heart contractions: 3 4 baroreceptors (stretching the walls of blood vessels) 5 6 7 vessels, medulla adrenal glands chemoreceptors stretching the walls of internal organs 1, 2 – vasomotor center of the medulla oblongata and pons and commands coming from it; 3 – regulatory influences of the hypothalamus, cerebral hemispheres and other structures of the central nervous system, as well as receptors; 4, 5 – wandering nuclei. nerve and their parasympathetic. action; 6, 7 – sympathetic effects ( spinal cord and ganglia): more extensive projections. In parallel, the influence of the sympathetic nervous system on the blood vessels (constriction) and the adrenal medulla (release of adrenaline) develops. 10
5 4 The main connections of the vasomotor center of the medulla oblongata and the pons (only sympathetic effects are shown at the output): 3 1 2 1. Vascular baroreceptors. 2. Peripheral chemoreceptors (chemo. RC). 3. Central chemo. RC. 4. Respiratory centers. 5. Influences of the hypothalamus (thermoregulation, pain and other innately significant stimuli, emotions) and the cerebral cortex (switched through the hypothalamus and midbrain; emotions associated with assessing the situation as potentially significant, dangerous, etc.; the center of such emotions is the cingulate Izv.). eleven
The function of baroreceptors when changing body position in space. The ability of baroreceptors to maintain a relatively constant blood pressure in the upper torso is especially important when a person stands up after a long period of standing. horizontal position. Immediately after standing up, blood pressure in the vessels of the head and upper torso decreases, which could lead to loss of consciousness. However, the decrease in pressure in the baroreceptor area immediately causes a sympathetic reflex response, which prevents a decrease in blood pressure in the vessels of the head and upper torso.
Sympathetic regulation of hemodynamics. The impulse from volume receptors and baroreceptors enters the brain stem through the fibers of the glossopharyngeal (IX pair) and vagus (X pair) nerves. This impulse causes inhibition of the stem sympathetic centers. The impulse traveling along the vagus nerves is switched in the nucleus of the solitary tract. (+) - stimulating effect; (-) - braking effect. JOP is the nucleus of the solitary tract.
Wiring department. Excitation from interoreceptors mainly occurs in the same trunks as the fibers of the autonomic nervous system. The first neurons are located in the corresponding sensory ganglia, the second neurons are in the spinal cord or medulla oblongata. Ascending Paths from them they reach the posteromedial nucleus of the thalamus (third neuron) and then rise to the cerebral cortex (fourth neuron). The vagus nerve transmits information from the receptors of the internal organs of the chest and abdominal cavity. Celiac nerve - from the stomach, intestines, mesentery. Pelvic nerve - from the pelvic organs.
Cortical department localized in zones C 1 and C 2 of the somatosensory cortex and in the orbital region of the cerebral cortex. The perception of some interoceptive stimuli may be accompanied by the appearance of clear, localized sensations, for example, when the walls of the bladder or rectum are stretched. But visceral impulses (from interoreceptors of the heart, blood vessels, liver, kidneys, etc.) may not cause clearly conscious sensations.
This is due to the fact that such sensations arise as a result of irritation of various receptors included in a particular organ system. In any case, changes in internal organs have a significant impact on emotional condition and the nature of human behavior.
In addition to a significant increase in blood pressure during physical activity and stress, the autonomic nervous system provides continuous control over blood pressure levels through numerous reflex mechanisms. Almost all of them operate on the principle of negative feedback.
Most studied nervous mechanism control of blood pressure is the baroreceptor reflex. The baroreceptor reflex occurs in response to stimulation of stretch receptors, which are also called baroreceptors or pressoreceptors. These receptors are located in the wall of some large arteries of the systemic circulation. An increase in blood pressure leads to stretching of the baroreceptors, the signals from which enter the central nervous system. Feedback signals are then sent to the centers of the autonomic nervous system, and from them to the blood vessels. As a result, the pressure drops to normal levels.
Baroreceptors are branched nerve endings located in the walls of arteries. They are excited when stretched. A number of baroreceptors are present in the wall of almost every major artery in the chest and neck. However, especially many baroreceptors are located: (1) in the wall of the internal carotid artery near the bifurcation (in the so-called carotid sinus); (2) in the wall of the aortic arch.
Signals from the carotid baroreceptors are carried along the very thin nerves of Hering to the glossopharyngeal nerve in the upper neck, and then along the fasciculus solitarius to the medullary portion of the brainstem. Signals from the aortic baroreceptors located in the aortic arch are also transmitted along the fibers of the vagus nerve to the solitary tract of the medulla oblongata.
Baroreceptor response to pressure changes. Different levels of blood pressure affect the frequency of impulses passing along the Hering sinocarotid nerve. Sinocarotid baroreceptors are not excited at all if the pressure ranges from 0 to 50-60 mm Hg. Art. When the pressure changes above this level, impulses in the nerve fibers progressively increase and reach a maximum frequency at a pressure of 180 mm Hg. Art. Aortic baroreceptors form a similar response, but begin to excite at a pressure level of 30 mmHg. Art. and higher.
The slightest deviation of blood pressure from the normal level (100 mm Hg) is accompanied by a sharp change in impulses in the fibers of the sinocarotid nerve, which is necessary to return blood pressure to normal levels. Thus, the baroreceptor feedback mechanism is most effective in the pressure range in which it is needed.
Baroreceptors respond extremely quickly to changes in blood pressure. The frequency of impulse generation in a fraction of a second increases during each systole and decreases in the arteries causes a reflex decrease in blood pressure both due to a decrease in peripheral resistance and due to a decrease cardiac output. Conversely, when blood pressure decreases, the opposite reaction occurs, aimed at increasing blood pressure to normal levels.
The ability of baroreceptors to maintain relatively constant blood pressure in the upper torso is especially important when a person stands up after a long period of lying in a horizontal position. Immediately after standing up, blood pressure in the vessels of the head and upper torso decreases, which could lead to loss of consciousness. However, the decrease in pressure in the baroreceptor area immediately causes a sympathetic reflex response, which prevents a decrease in blood pressure in the vessels of the head and upper torso.
7) Vasopressin. Vasopressin, or the so-called antidiuretic hormone, is a vasoconstrictor hormone. It is formed in the brain, in the nerve cells of the hypothalamus, then along the axons nerve cells transported to the posterior lobe of the pituitary gland, where it is eventually secreted into the blood.
Vasopressin could have a significant effect on circulatory function. However, very small amounts of vasopressin are normally secreted, so most physiologists believe that vasopressin does not play a significant role in the regulation of blood circulation. However, experimental studies have shown that the concentration of vasopressin in the blood after severe blood loss increases so much that it causes an increase in blood pressure of 60 mmHg. Art. and practically returns it to normal levels.
Important function Vasopressin is to enhance the reabsorption of water from the renal tubules into the bloodstream or, in other words, to regulate the volume of fluid in the body, so the hormone has a second name - antidiuretic hormone.
8) Renin-angiotensin system(RAS) or renin-angiotensin-aldosterone system (RAAS) is a hormonal system in humans and mammals that regulates blood pressure and blood volume in the body.
Renin is formed in the form of g-rorenin and is secreted in the juxtaglomerular apparatus (JGA) (from the Latin words juxta - about, glomerulus - glomerulus) of the kidneys by myoepithelioid cells of the afferent arteriole of the glomerulus, called juxtaglomerular (JGA). The structure of the UGA is shown in Fig. 6.27. In addition to the JGA, the JGA also includes the part of the distal tubule of the nephron adjacent to the afferent arterioles, the multilayered epithelium of which forms a dense spot here - macula densa. Renin secretion in the SGC is regulated by four main influences. Firstly, the amount of blood pressure in the afferent arteriole, i.e. the degree of its stretching. A decrease in stretch activates and an increase suppresses renin secretion. Secondly, the regulation of renin secretion depends on the sodium concentration in the urinary tubule, which is perceived by the macula densa - a kind of Na-receptor. The more sodium appears in the urine of the distal tubule, the higher the level of renin secretion. Thirdly, renin secretion is regulated by sympathetic nerves, the branches of which end in the JGC; the mediator norepinephrine stimulates renin secretion through beta-adrenergic receptors. Fourthly, the regulation of renin secretion is carried out according to a negative feedback mechanism, including the level in the blood of other components of the system - angiotensin and aldosterone, as well as their effects - the content of sodium and potassium in the blood, blood pressure, the concentration of prostaglandins in the kidney, formed under the influence of angiotensin.
In addition to the kidneys, renin formation occurs in the endothelium blood vessels many tissues, myocardium, brain, salivary glands, zona glomerulosa of the adrenal cortex.
Renin secreted into the blood causes the breakdown of alpha globulin in the blood plasma - angiotensinogen produced in the liver. In this case, a low-active decapeptide angiotensin-I is formed in the blood (Fig. 6.1-8), which in the vessels of the kidneys, lungs and other tissues is exposed to the action of a converting enzyme (carboxycathepsin, kininase-2), which cleaves two amino acids from angiotensin-1. The resulting octapeptide angiotensin-II has a large number various physiological effects, including stimulation of the zona glomerulosa of the adrenal cortex, which secretes aldosterone, which gave rise to calling this system the renin-angiotensin-aldosterone system.
Angiotensin-II, in addition to stimulating aldosterone production, has the following effects:
Causes narrowing arterial vessels,
Activates the sympathetic nervous system both at the level of centers and by promoting the synthesis and release of norepinephrine at synapses,
Increases myocardial contractility,
Increases sodium reabsorption and weakens glomerular filtration in the kidneys,
Promotes the formation of a feeling of thirst and drinking behavior.
Thus, the renin-angiotensin-aldosterone system is involved in the regulation of systemic and renal circulation, circulating blood volume, water-salt metabolism and behavior.
Localization of arterial baroreceptors. IN
The walls of the large intrathoracic and cervical arteries contain numerous baro-, or pressoreceptors, excited by sprain vessel walls under the influence of transmural pressure. The most important baroreceptor areas are the areas of the aortic arch and carotid sinus (Fig. 20.27).
Sensory fibers from the baroreceptors of the carotid sinus are part of the sinocarotid nerve branch glossopharyngeal nerve. Baroreceptors of the aortic arch inner-
verified left depressor (aortic) nerve, and baroreceptors of the area of origin of the brachiocephalic trunk - right depressor nerve. Both sinocarotid and aortic nerves also contain afferent fibers from chemoreceptors, located in the carotid bodies (near the branching area of the common carotid artery) and in the aortic bodies (aortic arch).
Dependence of arterial baroreceptor impulses on pressure. If vascular wall stretch under action permanent pressure, then impulses in the baroreceptors will be continuous, Moreover, the curve of the dependence of the frequency of this impulse on pressure has an almost S-shaped character. The section of the greatest slope of this curve falls on the range of pressure values from 80 to 180 mm Hg. Art. Baroreceptors act as proportional differential sensors: to fluctuations in blood pressure during cardiac cycle they react rhythmic volleys of discharges, the frequency of which changes the more, the higher the amplitude and/or growth rate of the pressure wave. As a result, the impulse frequency in the ascending part of the pressure curve is significantly higher than in the flatter descending part (Fig. 20.28). As a result of this “asymmetry” (more intense excitation of baroreceptors during increased pressure)
CHAPTER 20. FUNCTIONS OF THE VASCULAR SYSTEM 533
average frequency impulses are higher than at the same constant pressure. It follows that baroreceptors transmit information not only about mean arterial pressure, but also about amplitude pressure fluctuations and steepness its increase (and, consequently, about the heart rhythm).
Effect of arterial baroreceptor activity on blood pressure and cardiac function. Afferent impulses from baroreceptors travel to cardioinhibitory and vasomotor centers medulla oblongata (p. 542), as well as to other parts of the central nervous system. These impulses have inhibitory effect on the sympathetic centers And stimulating to parasympathetic. As a result, the tone of sympathetic vasoconstrictor fibers (or the so-called vasomotor tone), and frequency and strength of heart contractions(Fig. 20.28).
Since impulses from baroreceptors are observed in a wide range of blood pressure values, their inhibitory effects are manifested even at “normal” pressure. In other words, arterial baroreceptors exert a constant depressor action. As pressure increases, impulses from baroreceptors increase, and the vasomotor center inhibits
lives stronger; this leads to an even greater dilation of blood vessels, and the vessels of different areas expand in varying degrees. Dilatation of resistive vessels is accompanied by decrease in total peripheral resistance, and capacitive - increasing the capacity of the bloodstream. Both lead to a decrease in blood pressure, either directly or as a result of a decrease in central venous pressure and, therefore, stroke volume (Fig. 20.28). In addition, when baroreceptors are stimulated, the frequency and strength of heart contractions decrease, which also helps lower blood pressure. As pressure drops, impulses from baroreceptors decrease, and reverse processes develop, ultimately leading to an increase in pressure.
This autoregulatory homeostatic mechanism operates on the principle closed feedback loop(Fig. 20.29): signals from baroreceptors during short-term changes in blood pressure cause reflex changes in cardiac output and peripheral resistance, resulting in is being restored baseline pressure.
The role of reflexes from arterial baroreceptors in the normalization of blood pressure is particularly good
534 PART V. BLOOD AND THE CIRCULAR SYSTEM
This is visible in experiments on measuring blood pressure during the day (Fig. 20.30). The distribution curves of the obtained pressure values show that at intact sinocarotid nerves maximum density these values fall within narrow limits in the region “normal” average pressure - 100 mmHg (curve maximum). If, as a result of denervation of baroreceptors, homeostatic regulatory mechanisms are turned off, then the distribution curve of pressure values significantly stretches both towards larger and smaller values.
All these reflex mechanisms form an important link in general regulation of blood circulation. IN of this regulation, blood pressure is only one of the maintained constants.
If in an experiment artificially induce chronic hypertension, then after a few days the baroreceptors adapt To high blood pressure, completely preserving their functions. Under these conditions, autoregulatory mechanisms aimed at stabilizing blood pressure no longer lead to its reduction; on the contrary, they maintain pressure on high level, thereby contributing further development pathological disorders. Recently, attempts have been made to use the mechanisms of reflex regulation of blood pressure to treat patients with hypertension that cannot be controlled. drug therapy. For this purpose, the sinocarotid nerves were subjected to constant or synchronized
nomu with pulse irritation through implanted electrodes (“controlled pressure”).
At impact along the area of the carotid sinus or its compression from the outside, baroreceptors are excited, which leads to a decrease in blood pressure and a decrease in heart rate. In older people with severe atherosclerosis, this may result in a sharp drop in blood pressure and temporary cardiac arrest with loss of consciousness. (carotid sinus syndrome). In most cases, after 4-6 s heartbeat is restored, and in the first moments an atrioventricular rhythm is often observed (p. 456) and only then is normal restored sinus rhythm. However, if cardiac arrest continues for too long, death can occur. During attacks paroxysmal tachycardia(sharply accelerated pulse) it is sometimes possible to normalize the rhythm by pressing on the carotid sinus area on one or both sides.
The influence of baroreceptor activity on other parts of the central nervous system. An increase in impulses coming from baroreceptors to the vasomotor centers of the medulla oblongata leads to braking some parts of the central nervous system. At the same time, breathing becomes more shallow, decreases muscle tone and impulses arriving via γ-efferents to the muscle spindles, and monosynaptic reflexes are weakened. EEG is characterized by a tendency towards synchronization. In awake animals, with strong stretching of the carotid sinus region, a decrease in motor activity; sometimes they even fall asleep.
CHAPTER 20. FUNCTIONS OF THE VASCULAR SYSTEM 535
Effect of baroreceptor activity on blood volume. Reflex changes in the tone of pre- and postcapillary vessels affect effective hydrostatic pressure in the capillaries, thereby shifting the filtration-reabsorption equilibrium. When blood pressure increases, impulses from baroreceptors increase, which leads to reflex vasodilation; resulting in effective capillary pressure increases and speed increases filtering fluid into the interstitial space.
At decrease impulses from baroreceptors, reverse processes occur. All these reactions begin, perhaps, even before adaptive changes in general peripheral resistance and vascular capacity occur.
IN skeletal muscles ah, characterized by a significant total capillary surface area and an extremely variable volume of interstitial space, quite rapid movements of large volumes of fluid from the intravascular space to the interstitial space and vice versa are possible. During heavy muscular work, plasma volume can decrease by 10-15% in 15-20 minutes due to expansion of precapillaries. The opposite effect—an increase in the volume of intravascular fluid as a result of reabsorption from the interstitial space—is observed, for example, when blood pressure drops. This process also develops quickly, although after some time it becomes impossible to distinguish it from others regulatory mechanisms intermediate type of action (p. 537).
Nervous regulation of blood circulation carried out in the cardiovascular circulatory center, which is located in medulla oblongata. It includes the pressor (vasoconstrictor) and depressor (vasodilator) sections. It is mainly influenced by impulses from reflexogenic zones located in the carotid sinus, aortic arch, thyrocarotid and cardiopulmonary regions. Here are the receptors that perceive changes in blood pressure - baroreceptors and the chemical composition of the blood - chemoreceptors.
According to their chemical structure, receptors consist of proteins, nucleic acids and other compounds. Receptors are located on outer surface cell membrane, they transmit information from environment inside the cell.
The most studied in cardiology alpha adrenergic receptors And beta adrenergic receptors. Adrenaline and norepinephrine act on alpha-adrenergic receptors and cause vasoconstriction and increase. Adrenaline can also excite the beta-adrenergic receptors of some vessels, for example, the vessels of skeletal muscles, and causes them to dilate. Excitation of myocardial beta-adrenergic receptors by adrenaline and norepinephrine increases the frequency and strength of heart contractions. Many pharmacological preparations have the ability to block the action of agents that stimulate alpha-adrenergic receptors and beta-adrenergic receptors. Such drugs are called adrenergic blockers.
The carotid sinus is located at the beginning of the internal carotid artery. The nerve endings located in it are sensitive to stretching of the arterial wall when the pressure in the vessel increases. These baroreceptors are stretch receptors. Similar baroreceptors are present in the aortic arch, in pulmonary artery and its branches, in the chambers of the heart. Impulses from baroreceptors inhibit the sympathetic and excite the parasympathetic centers. As a result, the tone of sympathetic vasoconstrictor fibers decreases. There is a slowdown in the pulse, a decrease in the strength of heart contractions, and a decrease in peripheral vascular resistance, which causes a decrease in blood pressure.
In the bifurcation area carotid arteries chemoreceptors are located - the so-called aortic bodies, which are a reflexogenic zone that responds to chemical composition blood - partial pressure of oxygen and carbon dioxide. These chemoreceptors are especially sensitive to a lack of oxygen in the blood and hypoxia. Hypoxia increases their activity, this is accompanied by a reflex deepening of breathing, increased heart rate, and an increase in minute volume of blood circulation.
The fibers of the sympathetic nerves, with the help of mediators - adrenaline and norepinephrine - predominantly cause vasoconstriction and an increase in blood pressure. Parasympathetic nerve fibers, using the neurotransmitter acetylcholine, primarily cause vasodilation and a decrease in blood pressure. The innervation density of arteries is higher than that of veins.
Receptors that respond to pressure can be found in the walls of arteries. In some areas they are found in large quantities. These areas are called reflexogenic zones. There are three zones that are most important for the regulation of the circulatory system. They are located in the area of the aortic arch, in the carotid sinus and pulmonary artery. Receptors of other arteries, including the microvasculature, take part mainly in local redistribution reactions of the blood circulation.
Baroreceptors are stimulated when the vessel wall is stretched. The impulse from the baroreceptors of the aortic arch and carotid sinus increases almost linearly with increasing pressure from 80 mm Hg. Art. (10.7 kPa) up to 170 mm Hg. Art. (22.7 kPa). Moreover, not only the amplitude of vessel stretching matters, but also the rate of pressure growth. At constant high blood pressure receptors gradually adapt and the intensity of impulses weakens.
Afferent impulses from baroreceptors arrive from boulevard vasomotor neurons, where through excitation of the depressor section the pressor section is inhibited. As a result, the impulse of the sympathetic nerves weakens and the tone of the arteries, especially resistive ones, decreases. At the same time, blood flow resistance decreases, and the outflow of blood into further vessels increases. The pressure in the overlying arteries decreases. At the same time, the sympathetic tonic effect on the venous section decreases, which leads to an increase in its capacity. As a result, the blood flow from the veins to the heart and its stroke volume are reduced, which also contributes to direct impact on the heart of the bulbar region (impulses arrive vagus nerves). This reflex is probably triggered with each systolic ejection and contributes to the emergence of regulatory effects on peripheral vessels.
The opposite direction of the response is observed with a decrease in pressure. A decrease in impulse from baroreceptors is accompanied by an effector effect on blood vessels through the sympathetic nerves. In this case, a hormonal pathway of action on blood vessels may also be involved: due to intense impulses by sympathetic nerves, the release of catecholamines from the adrenal glands increases.
There are also baroreceptors in the vessels of the pulmonary circulation. There are three main receptor zones: the trunk of the pulmonary artery and its bifurcation, frequent sections of the pulmonary veins, and small vessels. The zone of the pulmonary artery trunk is especially important, during the period of stretching of which the reflex of dilatation of the vessels of the systemic circulation begins. At the same time, the heart rate decreases. This reflex is also realized through the above-mentioned bulbar structures.
Modulation of baroreceptor sensitivity
The sensitivity of baroreceptors to blood pressure varies depending on many factors. Thus, in the receptors of the carotid sinus, sensitivity increases with changes in the concentration of Na +, K + »Ca2 + in the blood and the activity of the Na-, K-pump. Their sensitivity is influenced by the impulse of the sympathetic nerve, which comes here, and changes in the level of adrenaline in the blood.
A particularly important role is played by compounds produced by the endothelium of the vascular wall. Thus, prostacyclin (PGI2) increases the sensitivity of carotid sinus baroreceptors, and relaxation factor (RF), on the contrary, suppresses it. The modular role of endothelial factors is obviously of greater importance for distorting the sensitivity of baroreceptors in pathology, in particular in the development of atherosclerosis and chronic hypertension. It is quite clear that normally the ratio of factors that increase and decrease the sensitivity of receptors is balanced. With the development of sclerosis, factors that reduce the sensitivity of baroreceptor zones predominate. As a result, reflex regulation is disrupted, thanks to which it is maintained normal level blood pressure, and hypertension develops.
