As a sympathetic nervous system affects the heart. Regulation of heart activity. Characteristics and mechanisms of influence of sympathetic and parasympathetic nerves on heart activity. The age features of the tone of the wandering nerves nuclei. Intracardial M.
The agreed activity of various organs and tissues provides the body sustainability and viability. The highest regulator of the activities of all organs of our body and primarily the heart and vessels is the cerebral bark. She is subordinated to the cerebral sites below, which are customary to call. It concentrates the reflex, to a certain extent independent of the will operations independent of the will.
It provides the implementation of the so-called unconditional reflexes - instincts (food, defensive, etc.), plays a large role in the manifestation of emotions - fear, anger, joy, etc. no less important for the activities of the subcortition Regulation of the most important life functions of the body - blood circulation, breathing, digestion , metabolism, etc.
The relevant centers in the subcortex are associated with various internal organs and tissues, in particular with the cardiovascular system, through the so-called vegetative, or autonomous, nervous system. Under the influence of the excitation of one of its two departments - a sympathetic or parasympathetic (wandering) change in different directions, the work of the heart and blood vessels.
From various organs in need of a strengthened blood flow, "signals" go to the central nervous system, and the corresponding pulses to the heart and blood vessels are directed from it. As a result, the supply of blood organs is strengthened, it is weakened depending on their need.
Vegetative nervous system It has a great influence on the activities of the cardiovascular system. The final branches of the sympathetic and wandering nerves are directly related to the nodes described above in the heart muscle and they affect the frequency, rhythm and strength of heart rate.
The excitation of sympathetic nerves causes the increase in heart cuts. At the same time, the momentum of the pulse on the muscle of the heart is also accelerated, blood vessels (except for heart) are narrowed, blood pressure rises.
The irritation of the wandering nerve lowers the excitability of the sinus node, so the heart beats less often. In addition, slows down (sometimes significantly) the impulse according to the atrial stomach beam, and with a very sharp irritation of the wandering nerve, the pulse is sometimes not held at all, and therefore there is a disunity between the atrium and ventricles (the so-called blockade).
Under normal conditions, i.e., with a moderate influence on the heart, the wandering nerve provides peace. Therefore, I. P. Pavlov spoke about the wandering nerve that "it can be called to a certain extent to the nerve of rest, the nerve regulating the rest of the heart."
The vegetative nervous system constantly affects the heart and blood vessels, affecting the frequency and power of heart cuts, as well as the size of the lumen of blood vessels. Heart and blood vessels also participate in numerous reflexes, which occur under the influence of irritations coming from the external environment or from the body itself. So, for example, heat involves the rhythm of heart cuts and expands blood vessels, the cold makes the heart beat slowly, narrows the vessels of the skin and therefore causes a pallor.
When we move or carry out difficult physical work, the heart beats faster and with more power, and when we are alone, it beats less often and weaker. The heart can stop due to the reflex irritation of the wandering nerve with a strong impact in the stomach. Very severe pain, tested in various body damage, also in the order of reflex can lead to the excitation of a wandering nerve and, therefore, to the fact that the heart will be reduced less.
When excited (verbal and other stimuli), the bark of large hemispheres of the brain and subcortical areas, for example, with strong fears, joy and other emotions, is involved in the excitation of one or another department of the autonomic nervous system - a sympathetic or parasympathetic (wandering) nerve. In this regard, the heart beats then more often, then less often, it is stronger, it is weaker, the blood vessels are narrowed, then they are expanding, the person will blush, it will be pale.
This usually takes part in the internal secretion gland, which themselves are influenced by the sympathetic and wandering nerves and in turn hormones affect these nerves.
Of all the above, it can be seen how multifaceted, multilateral is the connection of the cardiovascular system with nervous and chemical regulators, as the power of nerves over the cardiovascular system.
The vegetative nervous system is under the direct impact of the brain, from which the streams of different pulses are constantly going to it, which excite the sympathetic, then the wandering nerve. The "leading" role of the cerebral cortex in the regulation of all organs affects the fact that the activity of the heart varies depending on the need of the body in supplying blood. A healthy adult heart in peace is shrinking 60-80 times per minute. It takes during diastole (relaxation) and throws about 60-80 milliliters (cubic centimeters) in the vessels during systole (cut). And with a large physical voltage, when the working muscles need strengthened blood supply, the amount of blood emitted with each reduction can significantly increase (a well-trained athlete up to 2000 milliliters and even more).
We told how the heart works, how the frequency and power of heart rate changes. But as the blood circulation occurs in the whole body, how blood moves along the vessels of the whole organism, what strength make it move it all the time in a certain direction, at a certain speed, which maintains the pressure inside the blood vessels necessary for constant blood movements inside the blood vessels?
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M. N. Levi, P. Yu. Martin (M. N. Levy, P. Y. Martin)
Introduction
Both regions of the vegetative nervous system have a regulatory effect on various structural formation of the heart. The sympathetic department stimulates the heart activity, and parasympathetic-oppress. The central nervous system controls the relative levels of the activity of sympathetic and parasympathetic departments, usually according to the feedback mechanism, so that with an increase in the sympathetic activity, the activity of the parasympathetic nervous system is usually reduced and vice versa. In some parts of the heart, for example, in nodal tissue, parasympathetic effects prevail over sympathetic. However, in other areas, for example, in the myocardium of ventricles, the influence of the sympathetic department is usually expressed much stronger than parasympathetic. With the simultaneous activation of both departments, the effects of sympathetic and parasympathetic nerve systems are not addressed by a simple algebraic method, and the interaction of their effects cannot be expressed by linear dependence.
These and other properties of the neurohumoral regulation of the work of the heart are described in detail in this chapter. Over the past 10 years, several detailed reviews were published on this issue.
Anatomy of the nervous system of the heart
Between animals different species There are significant differences in the distribution of efferent vegetative nerve fibers in the heart. Anatomy of the nervous system of the heart is most intensively studied on dogs. A schematic image of a dog's heart innervation is shown in Fig. 22.1.
The bodies of preggaeer neurons of sympathetic fibers going to the heart are located in the intermediolatal columns of the first five-six breast segments of the spinal cord. A axons of preggangonary neurons come out of spinal cord As part of white connecting branches and pass into the ocolopotic sympathetic trunks. In the dog, most of the pregganese fibers are included in star gangli, located in the upper part of the oily-star sympathetic stems. Then they continue as part of a subclavian barrel and form synapses with postganglyonary neurons in the lower cervical ganglia. In animals of other species, for example, by the cat, most of the synapses between the pre- and postganglyonic neurons are located in the ganglia star. Postgangylionic sympathetic fibers go to the heart in the form of a complex plexus of small nerve beams. Separate beams contain both sympathetic and parasympathetic fibers.
Fig. 22.1. Upper thoracic sympathetic barrel and heart vegetative nerves of the right side of the dog. (Borrowed with modifications from work.)
The parts of parasympathetic heart innervation are also varied depending on the type of mammal. In some species, for example, the cat, the bodies of preggglyonary parasympathetic neurons are located almost exclusively in the double core. Most of the preggaera parasympathetic dog neurons are also located in this core, but some of them are localized in the Dorzal Motor Core. Pregganionic fibers come out of the skull, descend down the neck in the composition of common carotid shells (the fascial vagina surrounding the jugular vein, the overall carotid artery and the wandering nerve) and enter into the chest. In the dog (see Fig. 22.1) Parasympathetic fibers take place near the lower neck ganglion, they enter the heart plexus, forming a series of mixed nerve beams together with postganglyonic sympathetic fibers. The synapses between pre- and postganglyonary parasympathetic fibers are in ganglia, located in the tissue of the heart. These ganglia are the most numerous near the sinus-atrial (joint ventures) and atrial and ventricular (PZH) knots.
Neurohumoral Regulation of Heart Frequency
Sympathetic regulation
Increasing sympathetic activity causes an increase in heart rate (CSS). Noraderenalin (n),. The exemption from the sympathetic nerve endings in the joint venture increases the frequency of spontaneous excitations of the automatic cells of the node. This is achieved by increasing the angle of slope of slow diastolic depolarization, it is likely by increasing the flow of calcium during the phase 4 of the action potential. When using a long pulse sequence to stimulate heart sympathetic nerves, the heart rate begins to increase "^ Latent period is 1-3 s. The established level of heart rate is achieved only after 30-60 ° C after the start of the stimulation of sympathetic fibers (Fig. 22.2).
After stopping the stimulation of sympathetic fibers, the chronotropic effect gradually disappears, and the rhythm is returned; to the control layer (see Fig. 22.2). The main mechanisms for reducing the concentration on the released from the endings of sympathetic fibers, the absorption of the neurotiator is the same nervous endings and cardiomyocytes, as well as the diffusion of the neurotiator from the releases of the release to coronary blood flow. If the mechanism of repeated capture of the mediator by nerve fibers inhibit using specific blockers, for example cocaine, then the disappearance of the chronotropic reaction occurs significantly slower.
Fig. 22.2. Heart response (heart rate) of a narcotized dog for constant stimulation-hearty sympathetic nerves with a frequency of 20 Hz for 30 s. (Borrowed with modifications from work.)
The value of a positive chronotropic reaction to the stimulation of sympathetic fibers depends on the frequency of stimulation. The maximum effect is achieved at a stimulation frequency of about 20-30 Hz. The frequency of spontaneous activity of sympathetic nerves usually does not exceed 10 Hz.
The distribution of sympathetic fibers in various structures of the heart varies greatly. The sympathetic nerves of the right side of the body have a much stronger influence on the heart rate than the same nerves of the left side.
DetailsRegulation of tissue blood flow depending on the metabolic needs of tissues, local mechanisms of the tissues themselves are carried out. Nerve gemodynamic regulation mechanisms perform common functions such as redistribution of blood flow between different organs and tissues, strengthening or braking the pump function and, most importantly, quick control over the system level arterial pressure .
In the regulation of blood circulation, autonomous (vegetative) nervous system takes part.
An important role in regulating blood circulation plays a sympathetic nervous system. The parasympathetic nervous system also participates in the regulation of blood circulation, mainly in the regulation of the heart activity.
Sympathetic nervous system.
Sympathetic vascular fibers in the composition of spinal nerves depart from the chest and upper lumbar spinal cord segments. They follow the ganggles of the sympathetic trunk, which is located on both sides of the spine. Then the sympathetic fibers go in two directions:
- as part of specific sympathetic nerves that innervate blood vessels internal organs and the heart, as shown in the right part of the picture;
- as part of peripheral spinal nerves, which innervate blood vessels of the head, torso and limbs.
Sympathetic innervation of blood vessels.
In most tissues, all vessels (with the exception of capillaries, prokapillary sphincters and metaternoles) are innervated sympathetic nerve fibers (sympathetic vasoconstrictors).
Stimulation of sympathetic nerves of small arteries and arterioles leads to an increase in vascular resistance and, consequently, to a decrease in blood flow in tissues.
Stimulation of the sympathetic nerves of large blood vessels, especially veins, leads to a decrease in the volume of these vessels. This contributes to the progress of blood towards the heart and, therefore, plays an important role in the regulation of cardiac activity, which will be stated in the following chapters.
Sympathetic nerve fibers of the heart.
Sympathetic nerve fibers innervation and blood vessels, and heart. Sympathetic stimulation leads to strengthening cardiac activity by increasing the frequency and force of heart rate.
The role of parasympathetic nerve fibers.
Although the role of the parasympathetic nervous system in the regulation of many autonomous functions (for example, numerous functions of the digestive tract) is extremely large, it plays relatively small role in the regulation of blood circulation. The most significant is the regulation of heart rate With the help of parasympathetic nerve fibers going to the heart in the composition of wandering nerves.
Let's just say that the stimulation of parasympathetic nerves causes a significant reduction in heart rate and a slight decrease in abbreviation strength.
As part of the sympathetic nerves, a huge number of vasoconstrictor nerve fibers passes and quite a bit - vasodinating fibers. The vesseloring fibers innervate all the departments of the vascular system, but the density of their distribution in different fabrics Various. Sympathetic vesseloring effect is especially expressed in the kidneys, thin intestines, spleen and skin, but much less - in skeletal muscles and brain.
The vessels center of the brain controls the vasoconducting system.
It is located bilateral in reticular formation oblong brain and the bottom third of the bridge. The vessels center sends parasympathetic pulses by wandering nerves to the heart, as well as sympathetic impulses through the spinal cord and peripheral sympathetic nerves to almost all the arteries, arterioles and body veins.
Although the details of the organization of the Vasomotor Center are not yet clear, the experimental data allow you to select the following important functional zones in it.
1. Vasoconstrictor zonelocated bilateral in the upper front desk of the oblong brain. Axes of nerve cells located in this zone are tested in the spinal cord, where the pregganionic neurons of the sympathetic vasoconstrictor system are excited.
2. Vasodilative zonelocated bilateral in the lower veneer part of the oblong brain. Axons of nerve cells located in this zone are sent to the vasoconstrictor zone. They slow down the activity of the neurons of the vasoconducting zone and thus contribute to the extension of the vessels.
3. Sensory zone, Located bilateral in a beam of a single path in the posterior part of the oblong brain and the bridge. The neurons of this zone are obtained by signals running on sensitive nerve fibers from the cardiovascular system mainly in the composition of the wandering and language nerve. Signals emerging from the sensory zone control the activity of both the vasoconstrictor and vasodilating zones of the vessels center.
This is how reflex control over the circulatory system. An example is a baroreceptor reflex that controls the level of blood pressure.
Functional sympatholysis.
With functional sympatholysis, smooth muscle elements in the excitation focus are not capable of responding to a nervous signal while maintaining communication with the neuropal end. This is how the regulatory influence of the sympathetic nervous system is manifested, the overwhelming activity of stimulating nerve impulses.
Vegetative nervous system (VNS) - Department of the nervous system, regulating the activities of internal organs, glands of external and internal secretion, blood and lymphatic vessels. The first information about the structure and functions of the vegetative nervous system belongs to Galen (II century n. E.). J. Reil (1807) introduced the concept of "vegetative nervous system", and J. Langley (1889) gave a morphological description of the autonomic nervous system, proposed her division of her sympathetic and parasympathetic departments, introduced the term "autonomous nervous system", given the ability of the latter independently Processes regulating the activities of internal organs. Currently, in Russian, German, French-speaking literature, you can meet the term vegetative nervous system, and in the English-speaking-autonomous nervous system (ANC). The activity of the vegetative nervous system is mainly unprofitable and the consciousness is not directly controlled, aimed at maintaining the constancy of the inner medium and the adaptation of it to the changing conditions of the external environment.
Anatomy of the vegetative nervous system
From the point of view of the management hierarchy, the vegetative nervous system is conventionally divided by 4 floors (levels). The first floor is intramural plexuses, the second - paravertebral and excellent ganglia, the third - the central structures of the sympathetic nervous system (SNA) and the parasympathetic nervous system (PSNS). The latter are represented by the accumulations of pregganionic neurons in the brain barrel and the spinal cord. The fourth floor includes higher vegetative centers (limbico-reticular complex - Hippocampus, pear-shaped shutty, almond complex, partition, front cores of thalamus, hypothalamus, reticular formation, cerebellum, large semi-haze). The first three floors are formed segmental, and the fourth - the oversegment departments of the vegetative nervous system.
The brain cortex is the highest regulatory center of integrative activities, activating both motor and vegetative centers. The limbico-reticulous complex and the cerebellum are responsible for the coordination of vegetative, behavioral, emotional, neuroendocrine reactions of the organism. In the oblong brain, it is a cardiovascular - a vascular center combining parasympathetic (cardioengic), sympathetic (vasodepressor) and vasomotor centers, the regulation of which is carried out by subcortical nodes and cerebral cortex. The brain barrel constantly supports the vegetative tone. The sympathetic department of the vegetative nervous system causes the mobilization of the activities of vital organs, increases energy generation in the body, stimulates the work of the heart (the heart rate increases, the rate of conduct on specialized conductive tissues increases, the reduction of myocardium increases). The parasympathetic department of the vegetative nervous system has a trophhotropic effect, contributing to the restoration of the homoseostasis disturbed during the activity of the body, acts oppressingly on the heart (reduces heart rate, atrioventricular conductivity and myocardial cutness).
Heart rhythm is determined by the ability of specialized heart cells to be spontaneously activated, the so-called property of cardiac automatism. The automatism ensures the occurrence of electrical pulses in myocardium without the participation of nervous stimulation. Under normal conditions, the processes of spontaneous diastolic depolarization, which determine the properties of automatism, are most quickly leaked in the synoatrial node (SU). It is the synocatrial node that sets the heart rhythm, being a driver of 1 order rhythm. The usual frequency of sinus pulse formation is 60 - 100 pulses per minute, i.e. The automatism of the synocatrial node is not a constant value, it may vary in connection with the possible offset of the rhythm driver within the node. Currently, the heart rhythm is considered not only as an indicator of its own function of the rhythm of the synoatrial node, but to a greater extent as an integral marker of the state of a plurality of systems providing homeostasis of the body. Normally, the main imperative influence on the rhythm of the heart has a vegetative nervous system.
Heart innervation
Preggangional parasympathetic nerve fibers originate in the oblong brain, in the cells that are in the Dorsal Nucleus Dorsalis N. Vagi) or the double core (nucleusambigeus) x cranial nerve. Efferent fibers go down the neck, near the common carotid arteries and through the mediastinum, forming synapses with postganglyionary cells. Synaps form parasympathetic ganglia, located in general and mainly near the synoatrial nodes and an atrioventricular compound (ABC). The neurotiator excreted from postganglyonary parasympathetic fibers is acetylcholine. At the same time, irritation of the wandering nerve leads to a slowdown of diastolic depolarization of cells, reduces the frequency of heart cuts (CSS). With continuous stimulation of the wandering nerve, the latent reaction period is 50-200 ms, which is due to the action of acetylcholine into specific acetylcholynegic K + channels in the heart cells.
The permanent level of CSS is achieved through several heart cycles. Single stimulation of the wandering nerve or short series of pulses affects the heart rate during the subsequent 15-20 seconds, with a rapid return to the control level, due to the rapid degradation of acetylcholine in the region of the synoatrial node and the atrioventricular compound. The combination of 2 of the characteristic features of parasympathetic regulation - a short latent period and the rapid fading of the response allows it to carry out fast regulation and control over the operation of the synoatrial node and the atrioventricular connection with almost every reduction.
The fibers of the right wandering nerve innervate mainly the right atrium and especially abundantly, and the left-wing nerve is an atrioventricular connection. As a result, with irritation of the right wandering nerve, a negative chronotropic effect is more pronounced, and when the left stimulation is negative drromotropic.
Parasympathetic innervation of ventricles is poorly expressed mainly represented in the rear-lines of the steel ventricle. Therefore, under the ischemia or myocardial infarction of this area, bradycardia and hypotension, due to the excitation of a wandering nerve and are described in the literature as Reflex Betzold Yarisha.
Preggangional sympathetic fibers originate in the intermedialateral pillars 5-6 of the upper chest and 1-2 lower cervical segments of the spinal cord. The axons of preggonary and postganglyonary neurons are synapses in three cervical and stars of ganglia.
In the mediastinum, postganglyonural fibers of sympathetic and preggonary fibers of parasympathetic nerves are combined together, forming a complex nerve plexus of mixed efferent nerves that go to the heart. Postgangylionic sympathetic fibers reach the base of the heart in the adventitution of large vessels, where the extensive plexus of epicardia is formed. Then they pass through myocardium, along the coronary vessels. The neurotransmitter excreted from postganglyonic sympathetic fibers is norerained, the level of which is the same both in SU and in the field of right atrium.
The increase in sympathetic activity causes an increase in heart rate, accelerates cell membrane diastolic depolarization, shifts the rhythm driver to cells with the highest automatic activity. Incutimulation of sympathetic nerves of heart rate increases slowly, the latent reaction period is 1-3 s, and the established heart rate is achieved only after 30-60 s from the start of stimulation. The reaction rate is affected by the fact that the mediator is produced rather slowly nervous endings, and the impact on the heart is carried out through a relatively slow system of secondary messbands - adenylate cyclase. After stopping the stimulation, the chronotropic effect disappears gradually. The rate of disappearance of the effect of stimulation is determined by a decrease in the concentration of the norenaline intercellular space, which changes by the absorption of the latter by nerve endings, cardiomyocytes and the diffusion of the neurotransmitter to coronary blood flow. Sympathetic nerves are practically evenly distributed across all parts of the heart, with the maximum innervation of the right atrium area. The sympathetic nerves of the right side mainly innervate the front surface of the ventricles and Su, and the left is the rear surface of the ventricles and an atrioventricular compound.
The afferent innervation of the heart is carried out mainly by the myelinized fibers, which are in the composition of the wandering nerve. The receptor apparatus is mainly represented by mechanical and baroreceptors located in the right atrium, in the mouths of the pulmonary and hollow veins of atrial, ventricles, aortic arc, synolocarotine sine. According to the majority of researchers, the regulatory influences of PSNS on Su and atrioventricular compound are significantly superior to the effects of the SNA.
The ADS activity is under the influence of the central nervous system (CNS) on the feedback mechanism. Both systems are closely related to each other, and the nervous centers at the level of the barrel and the hemispheres of the brain can not be divided morphologically. The topmost level of interaction is carried out in the vessels, where the afferent signals from the cardiovascular system are processed and where the regulation of the efferent activity of the sympathetic and parasympathetic nervous activity occurs. In addition to integration at the CNS level, the interaction at the level of pre- and postsynaptic nerve endings also plays, which is confirmed by the results of anatomical and histological research. In recent studies, special cells containing large stocks of catecholamines are found, on which synapses formed by terminal endings of a vagus nerve are located, which indicates the possibility of direct impact of a wandering nerve on adrenergic receptors. It has been established that part inside the heart neurocytes have a positive reaction to monoaminoxidase, which indicates their role in the metabolism of norepinephrine.
Despite the in general, the effect of SNA and PSNS, while simultaneously activating both VNS departments, their effects are not addressed by a simple algebraic method and the interaction cannot be expressed by linear dependence. The literature describes several types of interaction of VNS departments. According to the principle of "accented antagonism", inhibiting the effect of this level of parasympathetic activity, the higher the higher level of sympathetic activity, and vice versa. On the other hand, when a certain result of the decline in activity in one department of VNS, an increase in the activity of another department on the principle of "functional synergy" occurs. In the study of vegetative reactivity, it is necessary to take into account the "law of the initial level", according to which the higher the initial level, the system, the smaller response is possible under the action of indignant incentives.
The state of the VNS departments undergo significant changes over the life of a person. In infancy, there is a significant predominance of sympathetic nervous influences in the functional immature immaturity of both LED units. The development of the sympathetic and parasympathetic departments of ANS after birth occurs intensively, and by the time of puberty, the location density nerve plexuses In various departments of the heart reaches highest indicators. At the same time, in people of young age, the dominance of parasympathetic influences that manifest themselves in the original Vagotonia is at rest.
Starting from the 4th decade of life, invalurative changes begin in the apparatus of sympathetic innervation, while maintaining the density of cholinergic nerve plexuses. Desimatic despathization processes lead to a decrease in the sympathetic activity and the density of the distribution of nerve plexuses on cardiomyocytes, smooth muscle cells, contributing to heterogeneity, the potential of the dependent membrane properties in the cells of the conductive system, the working myocardium, the walls of the vessels, the hypersensitivity of the receptor apparatus to catecholamines and can serve as the basis of arrhythmias, including and fatal. There are also sexual differences in a state of vegetative nervous tone.
So, in women of young and middle age (up to 55 years), the lower activity of the sympathetic nervous system is noted than in men of similar age. Thus, the vegetative innervation of various parts of the heart of heterogeneous and asymmetrical, has age and sexual differences. The agreed work of the heart is the result of the dynamic interaction of VNS departments.
Reflex Cardiac Regulation
The arterial baroreptor reflex is a key mechanism for short-term blood pressure regulation (AD). The optimal level of systemic blood pressure is one of the most important factors necessary for adequate work of the cardiovascular system. The afferent impulses from carotid sinus baroreceptors and the aortic arcs according to the branches of the Language nerve (IX pair) and the wandering nerve (x pair) are coming to the cardioengic and vascular center of the oblong brain and other CNS departments. The efferent shoulder of the baroreptor reflex is formed by sympathetic and parasympathetic nerves. The pulsation from baroreceptors increases at an increase in the absolute value of stretching and the rate of change in the stretching of receptors.
Increasing the frequency of impulsation from baroreceptors has an inhibitory effect on sympathetic centers and exciting to parasympathetic, which leads to a decrease in the vasomotor tone in resistive and capacitive vessels, a decrease in the frequency and force of heart rate. If the average hell is sharply reduced, the thound of the vagus nerve virtually disappears, the areflexic regulation is carried out solely due to changes in efferent sympathetic activity. At the same time, the total peripheral resistance of the vessels increases, the frequency and the power of heart abbreviations are increasing, aimed at restoring the initial level of blood pressure. Conversely, if the hell rises sharply, the sympathetic tone is completely oppressed, and the gradation of reflex regulation occurs only due to changes in the efferent regulation of Vagus.
Increased pressure in the ventricles causes irritation of subendocardial stretching receptors and activation of the parasympathetic cardioengic center, which leads to reflex bradycardia and vasodilation. Reflex Bebridge is characterized by an increase in the sympathetic tone with an increase in heart rate in response to an increase in intravascular blood volume and increase pressure in large veins and atrium right.
At the same time, there is an increase in heart rate, despite the accompanying poverty. In real life, the reflex baybridge prevails over the arterial baroreceptor reflex in the event of an increase in circulating blood volume. It is initially and with a decrease in the circulating blood volume, the baroreceptor reflex prevails over the reflex of the baybridge.
A number of factors involved in maintaining the organism homeostasis affect the reflex regulation of cardiac activity, in the absence of significant changes in the activity of VNS. These include chemoreceptor reflex, changes in blood electrolyte levels (potassium, calcium). The influence of the heart rate is also influenced by the respiratory phases: inhale causes the depression of a wandering nerve and acceleration of the rhythm, exhale - irritation of the wandering nerve and the slowdown of cardiac activity.
Thus, in ensuring vegetative homeostasis, a large number of diverse regulators are involved. According to most researchers, the heart rhythm is not only an indicator of the SU function, but also the integral marker of the state of a plurality of systems providing homoeostasis of the body, with the main modulating influence of VNS. Attempting to allocate and quantify the effect on the rhythm of the heart of each of the links - central, vegetative, humoral, reflex - undoubtedly, is an urgent task in cardiological practice, since its decision will allow to develop differential diagnostic criteria for cardiovascular pathology on the basis of a simple and affordable assessment. Heart rhythm states.
