The effect of physical activity on the human heart. The influence of physical activity on the human heart Changes in the activity of the heart during physical work

Physical activity causes changes in various body functions, the characteristics and extent of which depend on power, the nature of motor activity, the level of health and fitness. The effect of physical activity on a person can only be judged on the basis of a comprehensive account of the totality of reactions of the whole organism, including the reaction from the central nervous system (CNS), cardiovascular system (CVS), respiratory system, metabolism, etc. It should be emphasized that the severity changes in body functions in response to physical activity depend, first of all, on the individual characteristics of a person and his level of fitness. The development of fitness, in turn, is based on the process of adaptation of the body to physical activity. Adaptation is a set of physiological reactions that underlies the body’s adaptations to changes in environmental conditions and is aimed at maintaining the relative constancy of its internal environment - homeostasis.

The concepts of “adaptation, adaptability,” on the one hand, and “training, fitness,” on the other hand, have many common features, the main one of which is achieving a new level of performance. Adaptation of the body to physical activity consists of mobilizing and using the body’s functional reserves, improving existing physiological regulatory mechanisms. No new functional phenomena or mechanisms are observed during the adaptation process; simply existing mechanisms begin to work more perfectly, more intensively and more economically (lower heartbeat, deepening of breathing, etc.).

The adaptation process is associated with changes in the activity of the entire complex of functional systems of the body (cardiovascular, respiratory, nervous, endocrine, digestive, sensorimotor and other systems). Different types of physical exercise place different demands on individual organs and systems of the body. A properly organized process of performing physical exercises creates conditions for improving the mechanisms that maintain homeostasis. As a result of this, changes occurring in the internal environment of the body are quickly compensated, cells and tissues become less sensitive to the accumulation of metabolic products.

Among the physiological factors that determine the degree of adaptation to physical activity, indicators of the state of the systems that provide oxygen transport, namely the blood system and the respiratory system, are of great importance.

Blood and circulatory system

The adult human body contains 5–6 liters of blood. At rest, 40–50% of it does not circulate, being in the so-called “depot” (spleen, skin, liver). During muscular work, the amount of circulating blood increases (due to its release from the “depot”). Its redistribution occurs in the body: most of the blood rushes to actively working organs: skeletal muscles, heart, lungs. Changes in the composition of the blood are aimed at satisfying the body's increased need for oxygen. As a result of an increase in the number of red blood cells and hemoglobin, the oxygen capacity of the blood increases, i.e., the amount of oxygen carried in 100 ml of blood increases. When playing sports, blood mass increases, the amount of hemoglobin increases (by 1–3%), the number of red blood cells increases (by 0.5–1 million per cubic mm), the number of leukocytes and their activity increases, which increases the body’s resistance to colds and infections diseases. As a result of muscle activity, the blood coagulation system is activated. This is one of the manifestations of the body’s urgent adaptation to the effects of physical activity and possible injuries with subsequent bleeding. By programming this situation “proactively”, the body increases the protective function of the blood coagulation system.

Motor activity has a significant impact on the development and condition of the entire circulatory system. First of all, the heart itself changes: the mass of the heart muscle and the size of the heart increase. In trained people, the weight of the heart is on average 500 g, in untrained people - 300.

The human heart is extremely easy to train and needs it like no other organ. Active muscle activity promotes hypertrophy of the heart muscle and enlargement of its cavities. The heart volume of athletes is 30% greater than that of non-athletes. An increase in the volume of the heart, especially its left ventricle, is accompanied by an increase in its contractility, an increase in systolic and minute volumes.

Physical activity helps to change the activity of not only the heart, but also the blood vessels. Active motor activity causes expansion of blood vessels, a decrease in the tone of their walls, and an increase in their elasticity. During physical activity, the microscopic capillary network opens almost completely, which is only 30–40% active at rest. All this allows you to significantly accelerate blood flow and, therefore, increase the supply of nutrients and oxygen to all cells and tissues of the body.

The work of the heart is characterized by a continuous change of contractions and relaxations of its muscle fibers. Contraction of the heart is called systole, relaxation is called diastole. The number of heart contractions in one minute is the heart rate (HR). At rest, in healthy, untrained people, the heart rate is in the range of 60–80 beats/min, in athletes it is 45–55 beats/min and lower. A decrease in heart rate as a result of systematic exercise is called bradycardia. Bradycardia prevents “wear and tear of the myocardium and has important health benefits. During the day, during which there were no training or competitions, the sum of the daily heart rate in athletes is 15–20% less than in people of the same gender and age who do not engage in sports.

Muscular activity causes the heart rate to increase. During intense muscular work, heart rate can reach 180–215 beats/min. It should be noted that an increase in heart rate is directly proportional to the power of muscle work. The greater the power of work, the higher the heart rate. However, with the same power of muscle work, the heart rate of less trained individuals is significantly higher. In addition, when performing any motor activity, heart rate changes depending on gender, age, well-being, and training conditions (temperature, air humidity, time of day, etc.).

With each contraction of the heart, blood is ejected into the arteries under high pressure. As a result of the resistance of the blood vessels, its movement in them is created by pressure, called blood pressure. The highest pressure in the arteries is called systolic or maximum, the lowest is called diastolic or minimum. At rest in adults, systolic pressure is 100–130 mmHg. Art., diastolic - 60-80 mm Hg. Art. According to the World Health Organization, blood pressure is up to 140/90 mm Hg. Art. is normotonic, above these values is hypertensive, and below 100–60 mm Hg. Art. - hypotonic. During exercise, as well as after finishing a workout, blood pressure usually increases. The degree of its increase depends on the power of the physical activity performed and the person’s level of fitness. Diastolic pressure changes less pronounced than systolic pressure. After prolonged and very strenuous activity (for example, participation in a marathon), diastolic pressure (in some cases systolic) may be lower than before performing muscular work. This is due to the dilation of blood vessels in working muscles.

Important indicators of cardiac performance are systolic and cardiac output. Systolic blood volume (stroke volume) is the amount of blood ejected by the right and left ventricles with each contraction of the heart. Systolic volume at rest in trained individuals is 70–80 ml, in untrained individuals it is 50–70 ml. The greatest systolic volume is observed at a heart rate of 130–180 beats/min. When the heart rate is above 180 beats/min, it decreases significantly. Therefore, the best opportunities for training the heart are exercised at 130–180 beats/min. Minute blood volume - the amount of blood ejected by the heart in one minute depends on heart rate and systolic blood volume. At rest, minute blood volume (MBV) averages 5–6 liters, with light muscular work it increases to 10–15 liters, and with strenuous physical work in athletes it can reach 42 liters or more. An increase in IOC during muscle activity ensures an increased need for blood supply to organs and tissues.

Respiratory system

Changes in the parameters of the respiratory system during muscular activity are assessed by respiratory rate, vital capacity, oxygen consumption, oxygen debt and other more complex laboratory tests. Respiration rate (change of inhalation and exhalation and respiratory pause) - the number of breaths per minute. The respiratory rate is determined using a spirogram or chest movement. The average frequency in healthy individuals is 16–18 per minute, in athletes it is 8–12. During physical activity, the respiratory rate increases on average 2–4 times and amounts to 40–60 respiratory cycles per minute. As breathing increases, its depth inevitably decreases. Depth of breathing is the volume of air during a quiet inhalation and exhalation during one respiratory cycle. The depth of breathing depends on the height, weight, chest size, level of development of the respiratory muscles, functional state and degree of training of the person. Vital capacity (VC) is the largest volume of air that can be exhaled after maximum inhalation. In women, vital capacity is on average 2.5–4 l, in men - 3.5–5 l. Under the influence of training, vital capacity increases; in well-trained athletes it reaches 8 liters. Minute volume of respiration (MVR) characterizes the function of external respiration and is determined by the product of respiratory frequency and tidal volume. At rest, MOD is 5–6 l; with intense physical activity it increases to 120–150 l/min or more. During muscular work, tissues, especially skeletal muscles, require significantly more oxygen than at rest and produce more carbon dioxide. This leads to an increase in MOU, both due to increased respiration and due to an increase in tidal volume. The harder the work, the relatively greater the MOU (Table 2.2).

Table 2.2

Average cardiovascular response rates

and respiratory systems to physical activity

Options		During intense physical activity
Heart rate	50–75 beats/min	160–210 beats/min
Systolic blood pressure	100–130 mm Hg. Art.	200–250 mm Hg. Art.
Systolic blood volume		150–170 ml and above
Minute blood volume (MBV)		30–35 l/min and above
Breathing rate	14 times/min	60–70 times/min
Alveolar ventilation (effective volume)		120 l/min or more
Minute breathing volume		120–150 l/min

Maximum oxygen consumption(MIC) is the main indicator of the productivity of both the respiratory and cardiovascular (in general, cardio-respiratory) systems. MOC is the greatest amount of oxygen that a person is able to consume within one minute per 1 kg of weight. MIC is measured by the number of milliliters per 1 minute per 1 kg of weight (ml/min/kg). MOC is an indicator of the body's aerobic capacity, i.e. the ability to perform intense muscular work, providing energy expenditure due to oxygen absorbed directly during work. The MIC value can be determined by mathematical calculation using special nomograms; possible in laboratory conditions when working on a bicycle ergometer or climbing a step. MOC depends on age, the state of the cardiovascular system, and body weight. To maintain health, you must have the ability to consume oxygen at least 1 kg - for women at least 42 ml/min, for men - at least 50 ml/min. When tissue cells receive less oxygen than is needed to fully meet energy needs, oxygen starvation, or hypoxia, occurs.

Oxygen debt- this is the amount of oxygen that is required to oxidize metabolic products formed during physical work. During intense physical activity, metabolic acidosis of varying severity is usually observed. Its cause is “acidification” of the blood, i.e. the accumulation of metabolic metabolites (lactic, pyruvic acids, etc.) in the blood. To eliminate these metabolic products, oxygen is needed - an oxygen demand is created. When oxygen demand is higher than current oxygen consumption, an oxygen debt is formed. Untrained people are able to continue working with an oxygen debt of 6–10 liters; athletes can perform such a load, after which an oxygen debt of 16–18 liters or more occurs. The oxygen debt is eliminated after completion of work. The time for its elimination depends on the duration and intensity of the previous work (from several minutes to 1.5 hours).

Digestive system

Systematically performed physical activity increases metabolism and energy, increases the body's need for nutrients that stimulate the secretion of digestive juices, activates intestinal motility, and increases the efficiency of digestive processes.

However, during intense muscular activity, inhibitory processes can develop in the digestive centers, reducing the blood supply to various parts of the gastrointestinal tract and digestive glands due to the fact that it is necessary to provide blood to the hard-working muscles. At the same time, the very process of actively digesting large amounts of food within 2–3 hours after eating it reduces the effectiveness of muscle activity, since the digestive organs in this situation seem to be in greater need of increased blood circulation. In addition, a full stomach raises the diaphragm, thereby complicating the functioning of the respiratory and circulatory organs. That is why the physiological pattern requires taking food 2.5–3.5 hours before the start of training, and 30–60 minutes after it.

Excretory system

During muscular activity, the role of excretory organs, which perform the function of preserving the internal environment of the body, is significant. The gastrointestinal tract removes the remnants of digested food; gaseous metabolic products are removed through the lungs; sebaceous glands, secreting sebum, form a protective, softening layer on the surface of the body; The lacrimal glands provide moisture that moistens the mucous membrane of the eyeball. However, the main role in ridding the body of metabolic end products belongs to the kidneys, sweat glands and lungs.

The kidneys maintain the necessary concentration of water, salts and other substances in the body; remove the end products of protein metabolism; produce the hormone renin, which affects the tone of blood vessels. During heavy physical exertion, the sweat glands and lungs, increasing the activity of the excretory function, significantly help the kidneys in removing decay products from the body that are formed during intensive metabolic processes.

Nervous system in motion control

When controlling movements, the central nervous system carries out very complex activities. To perform clear, purposeful movements, it is necessary to continuously receive signals to the central nervous system about the functional state of the muscles, the degree of their contraction and relaxation, body posture, the position of the joints and the angle of bend in them. All this information is transmitted from the receptors of the sensory systems and especially from the receptors of the motor sensory system located in muscle tissue, tendons, and joint capsules. From these receptors, according to the feedback principle and the mechanism of the central nervous system reflex, complete information is received about the execution of a motor action and its comparison with a given program. With repeated repetition of a motor action, impulses from the receptors reach the motor centers of the central nervous system, which accordingly change their impulses going to the muscles in order to improve the learned movement to the level of a motor skill.

Motor skill- a form of motor activity developed according to the mechanism of a conditioned reflex as a result of systematic exercises. The process of forming a motor skill goes through three phases: generalization, concentration, automation.

Phase generalization characterized by expansion and intensification of excitation processes, as a result of which extra muscle groups are involved in the work, and the tension of the working muscles turns out to be unreasonably high. In this phase, movements are constrained, uneconomical, imprecise and poorly coordinated.

Phase concentrations characterized by a decrease in excitation processes due to differentiated inhibition, concentrating in the desired areas of the brain. Excessive tension in movements disappears, they become precise, economical, performed freely, without tension, and stably.

In phase automation the skill is refined and consolidated, the execution of individual movements becomes as if automatic and does not require control of consciousness, which can be switched to the environment, search for solutions, etc. An automated skill is distinguished by high accuracy and stability of all its component movements.

Question 1 Phases of the cardiac cycle and their changes during physical activity. 3

Question 2 Motility and secretion of the large intestine. Absorption in the large intestine, the influence of muscle work on digestive processes. 7

Question 3 The concept of the respiratory center. Mechanisms of breathing regulation. 9

Question 4 Age-related features of the development of the motor system in children and adolescents 11

List of used literature... 13

Question 1 Phases of the cardiac cycle and their changes during physical activity

In the vascular system, blood moves due to a pressure gradient: from high to low. Blood pressure is determined by the force with which the blood in the vessel (heart cavity) presses in all directions, including on the walls of this vessel. The ventricles are the structure that creates this gradient.

The cyclically repeated change of states of relaxation (diastole) and contraction (systole) of the heart is called the cardiac cycle. With a heart rate of 75 per minute, the duration of the entire cycle is about 0.8 s.

It is more convenient to consider the cardiac cycle starting from the end of the total diastole of the atria and ventricles. In this case, the parts of the heart are in the following state: the semilunar valves are closed, and the atrioventricular valves are open. Blood from the veins flows freely and completely fills the cavities of the atria and ventricles. The blood pressure in them is the same as in nearby veins, about 0 mm Hg. Art.

Excitation, originating in the sinus node, first of all comes to the atrial myocardium, since its transmission to the ventricles in the upper part of the atrioventricular node is delayed. Therefore, atrial systole occurs first (0.1 s). In this case, the contraction of muscle fibers located around the mouths of the veins blocks them. A closed atrioventricular cavity is formed. When the atrial myocardium contracts, the pressure in them increases to 3-8 mm Hg. Art. As a result, part of the blood from the atria passes through the open atrioventricular openings into the ventricles, bringing the blood volume in them to 110-140 ml (ventricular end-diastolic volume - EDV). At the same time, due to the additional portion of blood received, the cavity of the ventricles is somewhat stretched, which is especially pronounced in their longitudinal direction. After this, ventricular systole begins, and diastole begins in the atria.

After an atrioventricular delay (about 0.1 s), excitation along the fibers of the conduction system spreads to the ventricular cardiomyocytes, and ventricular systole begins, lasting about 0.33 s. Ventricular systole is divided into two periods, and each of them into phases.

The first period - the period of tension - continues until the semilunar valves open. To open them, the blood pressure in the ventricles must be raised to a level greater than in the corresponding arterial trunks. In this case, the pressure, which is recorded at the end of ventricular diastole and is called diastolic pressure, in the aorta is about 70-80 mm Hg. Art., and in the pulmonary artery - 10-15 mm Hg. Art. The voltage period lasts about 0.08 s.

It begins with the asynchronous contraction phase (0.05 s), since not all ventricular fibers begin to contract at the same time. The first to contract are cardiomyocytes located near the fibers of the conduction system. This is followed by the phase of isometric contraction (0.03 s), which is characterized by the involvement of the entire ventricular myocardium in contraction.

The onset of ventricular contraction leads to the fact that, with the semilunar valves still closed, blood rushes to the area of lowest pressure - back towards the atria. The atrioventricular valves located in its path are slammed shut by the blood flow. Tendon threads keep them from dislocating into the atria, and contracting papillary muscles create even greater emphasis. As a result, closed ventricular cavities appear for some time. And until the contraction of the ventricles raises the blood pressure in them above the level required to open the semilunar valves, a significant shortening of the length of the fibers does not occur. Only their internal tension increases.

The second period - the period of blood expulsion - begins with the opening of the aortic and pulmonary artery valves. It lasts 0.25 s and consists of phases of fast (0.1 s) and slow (0.13 s) expulsion of blood. The aortic valves open at a pressure of about 80 mmHg. Art., and pulmonary - 10 mm Hg. Art. The relatively narrow openings of the arteries are not able to immediately pass the entire volume of ejected blood (70 ml), and therefore the developing contraction of the myocardium leads to a further increase in blood pressure in the ventricles. In the left it increases to 120-130 mm Hg. Art., and in the right - up to 20-25 mm Hg. Art. The resulting high pressure gradient between the ventricle and the aorta (pulmonary artery) promotes the rapid release of part of the blood into the vessel.

However, the relatively small capacity of the vessels, which previously contained blood, leads to their overflow. Now the pressure is growing in the vessels. The pressure gradient between the ventricles and vessels gradually decreases, as the rate of blood expulsion slows.

Due to the lower diastolic pressure in the pulmonary artery, the opening of the valves and the expulsion of blood from the right ventricle begin somewhat earlier than from the left. And a lower gradient leads to the fact that the expulsion of blood ends a little later. Therefore, the systole of the right ventricle is 10-30 ms longer than the systole of the left.

Finally, when the pressure in the vessels rises to the level of pressure in the ventricular cavity, the expulsion of blood ends. By this time, the contraction of the ventricles stops. Their diastole begins, lasting about 0.47 s. Usually, by the end of systole, about 40-60 ml of blood remains in the ventricles (end-systolic volume - ESV). The cessation of expulsion leads to the fact that the blood in the vessels with a reverse flow closes the semilunar valves. This condition is called the proto-diastolic interval (0.04 s). Then a decrease in tension occurs - an isometric period of relaxation (0.08 s).

By this time, the atria are already completely filled with blood. Atrial diastole lasts about 0.7 s. The atria are filled mainly with blood passively flowing through the veins. But it is also possible to identify an “active” component, which manifests itself in connection with the partial coincidence of their diastole with ventricular systole. When the latter contract, the plane of the atrioventricular septum shifts towards the apex of the heart, which creates a suction effect.

When the tension in the ventricular walls decreases and the pressure in them drops to 0, the atrioventricular valves open with blood flow. The blood filling the ventricles gradually straightens them. The period of filling the ventricles with blood can be divided into phases of fast and slow filling. Before the start of a new cycle (atrial systole), the ventricles, like the atria, have time to completely fill with blood. Therefore, due to the flow of blood during atrial systole, the intraventricular volume increases by approximately 20-30%. But this contribution increases significantly with intensification of the heart’s work, when the total diastole is shortened and the blood does not have time to sufficiently fill the ventricles.

During physical work, the activity of the cardiovascular system is activated and, thus, the increased need of working muscles for oxygen is more fully satisfied, and the resulting heat is removed through the bloodstream from the working muscle to those parts of the body where it is released. 3-6 minutes after the start of light work, a stationary (sustainable) increase in heart rate occurs, which is caused by the irradiation of excitation from the motor zone of the cortex to the cardiovascular center of the medulla oblongata and the receipt of activating impulses to this center from the chemoreceptors of working muscles. Activation of the muscular system increases blood supply to working muscles, which reaches a maximum within 60-90 s after the start of work. With light work, a correspondence is formed between blood flow and the metabolic needs of the muscle. As light dynamic work progresses, the aerobic pathway of ATP resynthesis begins to dominate, using glucose, fatty acids and glycerol as energy substrates. During heavy dynamic work, the heart rate increases to a maximum as fatigue develops. Blood flow in working muscles increases 20-40 times. However, delivery of O3 to muscles lags behind the needs of muscle metabolism, and part of the energy is generated through anaerobic processes.

Question 2 Motility and secretion of the large intestine. Absorption in the large intestine, the effect of muscle work on digestive processes

The motor activity of the large intestine has features that ensure the accumulation of chyme, its thickening due to the absorption of water, the formation of feces and their removal from the body during defecation.

The time characteristics of the process of movement of contents through parts of the gastrointestinal tract are judged by the movement of an x-ray contrast agent (for example, barium sulfate). After administration, it begins to enter the cecum after 3-3.5 hours. Within 24 hours, the colon is filled, which is freed from the contrast mass after 48-72 hours.

The initial sections of the colon are characterized by very slow small pendulum-like contractions. With their help, the chyme is mixed, which accelerates the absorption of water. In the transverse colon and sigmoid colon, large pendulum-like contractions are observed, caused by the excitation of a large number of longitudinal and circular muscle bundles. Slow movement of the contents of the colon in the distal direction is carried out due to rare peristaltic waves. The retention of chyme in the colon is facilitated by antiperistaltic contractions, which move the contents in a retrograde direction and thereby promote the absorption of water. Thickened, dehydrated chyme accumulates in the distal colon. This section of the intestine is separated from the overlying one, filled with liquid chyme, by a constriction caused by contraction of circular muscle fibers, which is an expression of segmentation.

When the transverse colon is filled with condensed dense contents, irritation of the mechanoreceptors of its mucous membrane increases over a large area, which contributes to the emergence of powerful reflex propulsive contractions that move a large amount of contents into the sigmoid and rectum. Therefore, this kind of contraction is called mass contraction. Eating accelerates the occurrence of propulsive contractions due to the implementation of the gastrocolic reflex.

The listed phase contractions of the large intestine are carried out against the background of tonic contractions, which normally last from 15 s to 5 min.

The basis of the motility of the large intestine, as well as the small intestine, is the ability of the membrane of smooth muscle elements to spontaneous depolarization. The nature of contractions and their coordination depend on the influence of efferent neurons of the intraorgan nervous system and the autonomic part of the central nervous system.

Absorption of nutrients in the large intestine under normal physiological conditions is insignificant, since most of the nutrients have already been absorbed in the small intestine. The size of water absorption in the large intestine is large, which is essential in the formation of feces.

Small amounts of glucose, amino acids, and some other easily absorbed substances can be absorbed in the large intestine.

Juice secretion in the large intestine is mainly a reaction in response to local mechanical irritation of the mucous membrane by chyme. Colon juice consists of dense and liquid components. The dense component includes mucous lumps consisting of desquamated epithelial cells, lymphoid cells and mucus. The liquid component has a pH of 8.5-9.0. Juice enzymes are contained mainly in desquamated epithelial cells, during the breakdown of which their enzymes (pentidases, amylase, lipase, nuclease, cathepsins, alkaline phosphatase) enter the liquid component. The content of enzymes in the juice of the colon and their activity are significantly lower than in the juice of the small intestine. But the available enzymes are sufficient to complete the hydrolysis of undigested food substances in the proximal parts of the colon.

Regulation of juice secretion from the mucous membrane of the large intestine is carried out mainly through enteral local nervous mechanisms.

Related information.

Human physical activity that requires more energy than is produced at rest is physical activity. During physical activity, the internal environment of the body changes, as a result of which homeostasis is disrupted. The energy requirement of muscles is provided by a complex of adaptation processes in various tissues of the body. The chapter examines the physiological parameters that change under the influence of acute physical activity, as well as the cellular and systemic adaptation mechanisms that underlie repeated or chronic muscle activity.

ASSESSMENT OF MUSCLE ACTIVITY

A single episode of muscular work or “acute exercise” causes responses in the body that differ from the reactions that occur during chronic exercise, in other words when training. Forms of muscular work can also vary. The amount of muscle mass involved in the work, the intensity of the efforts, their duration and the type of muscle contractions (isometric, rhythmic) influence the body's responses and the characteristics of adaptive reactions. The main changes that occur in the body during physical activity are associated with increased energy consumption by skeletal muscles, which can increase from 1.2 to 30 kcal/min, i.e. 25 times. Since it is impossible to directly measure ATP consumption during physical activity (it occurs at the subcellular level), an indirect assessment of energy costs is used - measurement oxygen taken in during respiration. In Fig. Figure 29-1 shows oxygen consumption before, during and after light, steady work.

Rice. 29-1. Oxygen consumption before, during and after light exercise.

Oxygen uptake and, consequently, ATP production increase until a steady state is reached in which ATP production is adequate to its consumption during muscle work. A constant level of oxygen consumption (ATP formation) is maintained until the work intensity changes. There is a delay between the start of work and the increase in oxygen consumption to some constant level, called oxygen debt or deficiency. Oxygen deficiency- the period of time between the beginning of muscle work and the increase in oxygen consumption to a sufficient level. In the first minutes after contraction, there is an excess of oxygen absorption, the so-called oxygen debt(See Figure 29-1). “Excess” oxygen consumption during the recovery period is the result of many physiological processes. During dynamic work, each person has his own limit of maximum muscle load, at which oxygen absorption does not increase. This limit is called maximum oxygen uptake (VO 2ma J. It is 20 times the oxygen consumption at rest and cannot be higher, but with appropriate training it can be increased. Maximum oxygen uptake, other things being equal, decreases with age, bed rest and obesity.

Responses of the cardiovascular system to physical activity

As energy expenditure increases during physical work, more energy production is required. Oxidation of nutrients produces this energy, and the cardiovascular system delivers oxygen to working muscles.

Cardiovascular system under dynamic load conditions

Local control of blood flow ensures that only working muscles with increased metabolic demands receive more blood and oxygen. If only the lower extremities are worked, the leg muscles receive an increased amount of blood, while the blood flow to the upper extremity muscles remains unchanged or reduced. At rest, skeletal muscle receives only a small fraction of cardiac output. At dynamic load both total cardiac output and relative and absolute blood flow to working skeletal muscles are significantly increased (Table 29-1).

Table 29-1.Distribution of blood flow at rest and under dynamic load in an athlete

Region	Rest, ml/min	%	%
Internal organs
Kidneys
Coronary vessels
Skeletal muscles	1200		22,0
Leather
Brain
Other organs
Total cardiac output			25,65

During dynamic muscular work, control of the cardiovascular system involves systemic regulation (the cardiovascular centers in the brain, with their autonomic effector nerves to the heart and resistive vessels) together with local regulation. Already before the start of muscle activity, it

the program is formed in the brain. First of all, the motor cortex is activated: the overall activity of the nervous system is approximately proportional to muscle mass and its working intensity. Under the influence of signals from the motor cortex, the vasomotor centers reduce the tonic effect of the vagus nerve on the heart (and therefore the heart rate increases) and switch the arterial baroreceptors to a higher level. In actively working muscles, lactic acid is formed, which stimulates the muscle afferent nerves. Afferent signals enter the vasomotor centers, which increase the influence of the sympathetic system on the heart and systemic resistive vessels. Simultaneously muscle chemoreflex activity inside the working muscles lowers Po 2, increases the content of nitric oxide and vasodilating prostaglandins. As a result, a complex of local factors dilates arterioles, despite an increase in sympathetic vasoconstrictor tone. Activation of the sympathetic system increases cardiac output, and local factors in the coronary vessels ensure their expansion. High sympathetic vasoconstrictor tone limits blood flow to the kidneys, visceral vessels, and inactive muscles. Blood flow in inactive areas can drop by up to 75% under heavy work conditions. An increase in vascular resistance and a decrease in blood volume help maintain blood pressure during dynamic exercise. In contrast to reduced blood flow in visceral organs and inactive muscles, the self-regulatory mechanisms of the brain keep blood flow at a constant level, regardless of the load. Skin vessels remain constricted only until there is a need for thermoregulation. During overexertion, sympathetic activity can limit vasodilation in working muscles. Prolonged work at high temperatures is associated with increased blood flow in the skin and intense sweating, leading to a decrease in plasma volume, which can cause hyperthermia and hypotension.

Responses of the cardiovascular system to isometric exercise

Isometric exercise (static muscle activity) causes slightly different cardiovascular responses. Blood

Muscle flow and cardiac output increase compared to rest, but high mean intramuscular pressure limits the increase in blood flow compared with rhythmic work. In a statically contracted muscle, intermediate metabolic products appear very quickly under conditions of too weak an oxygen supply. Under conditions of anaerobic metabolism, lactic acid production increases, the ADP/ATP ratio increases, and fatigue develops. Maintaining only 50% of maximum oxygen consumption is already difficult after the 1st minute and cannot last more than 2 minutes. Long-term steady voltage levels can be maintained at 20% of maximum. Factors of anaerobic metabolism under conditions of isometric exercise trigger muscle chemoreflex responses. Blood pressure increases significantly, and cardiac output and heart rate are lower than during dynamic work.

Reactions of the heart and blood vessels to single and constant muscle loads

A single intense muscular work activates the sympathetic nervous system, which increases the frequency and contractility of the heart in proportion to the effort expended. Increased venous return also contributes to cardiac performance during dynamic work. This includes the “muscle pump,” which compresses the veins during rhythmic muscle contractions, and the “respiratory pump,” which increases intrathoracic pressure oscillations from inhalation to inhalation. The maximum dynamic load causes the maximum heart rate: even blockade of the vagus nerve cannot increase the heart rate any more. Stroke volume reaches its ceiling at moderate work and does not change when moving to the maximum level of work. An increase in blood pressure, an increase in contraction frequency, stroke volume and myocardial contractility that occurs during work increases the myocardial need for oxygen. The linear increase in coronary blood flow during work can reach a value 5 times higher than the initial level. Local metabolic factors (nitric oxide, adenosine and activation of ATP-sensitive K channels) have a vasodilatory effect on coronary resistances.

tive vessels. Oxygen uptake in the coronary vessels at rest is high; it increases during operation and reaches 80% of the oxygen delivered.

Adaptation of the heart to chronic muscle overload largely depends on whether the work performed carries the risk of pathological conditions. Examples include increased left ventricular volume when work requires high blood flow and left ventricular hypertrophy is created by high systemic blood pressure (high afterload). Consequently, in people adapted to prolonged, rhythmic physical activity, which is accompanied by relatively low blood pressure, the left ventricle of the heart has a large volume with normal thickness of its walls. In people accustomed to prolonged isometric contractions, the thickness of the wall of the left ventricle is increased with normal volume and increased pressure. The large volume of the left ventricle in people engaged in constant dynamic work causes a slowdown in the rhythm and an increase in cardiac output. At the same time, the tone of the vagus nerve increases and decreasesβ - adrenergic sensitivity. Endurance training partially alters myocardial oxygen consumption, thereby influencing coronary blood flow. Myocardial oxygen uptake is approximately proportional to the ratio of heart rate times mean arterial pressure, and since exercise decreases heart rate, coronary blood flow under standard fixed submaximal exercise conditions decreases in parallel. Exercise, however, increases peak coronary blood flow, tightening myocardial capillaries, and increases capillary exchange capacity. Training also improves endothelium-mediated regulation, optimizes responses to adenosine, and intracellular free calcium control in coronary SMCs. Preservation of the vasodilator function by the endothelium is the most important factor determining the positive effect of chronic physical activity on coronary circulation.

Effect of physical training on blood lipids

Constant dynamic muscular work is associated with an increase in the level of circulating high-density lipoproteins.

ness (HDL) and a decrease in low-density lipoproteins (LDL). In this regard, the ratio of HDL and total cholesterol increases. Such changes in cholesterol fractions are observed at any age, provided that physical activity is regular. Body weight decreases and insulin sensitivity increases, which is typical for people with a sedentary lifestyle who begin regular physical exercise. In people who are at risk for coronary heart disease due to very high lipoprotein levels, exercise is a necessary addition to dietary restrictions and a means of losing weight, which helps lower LDL. Regular exercise improves fat metabolism and increases cellular metabolic capacity, favoringβ -oxidation of free fatty acids, and also improves lipoprotease function in muscle and adipose tissue. Changes in lipoprotein lipase activity, together with an increase in lecithin-cholesterol acyltransferase activity and apolipoprotein A-I synthesis, increase circulating levels

HDL.

Regular physical activity in the prevention and treatment of certain cardiovascular diseases

Changes in the ratio of HDL total cholesterol that occur with regular physical activity reduce the risk of developing atherosclerosis and coronary artery disease in active people compared with sedentary people. It has been established that cessation of vigorous physical activity is a risk factor for coronary artery disease, which is as significant as hypercholesterolemia, high blood pressure and smoking. The risk decreases, as noted earlier, due to changes in the nature of lipid metabolism, a decrease in the need for insulin and increased sensitivity to insulin, as well as due to a decrease inβ - adrenergic reactivity and increased tone of the vagus nerve. Regular muscle exercise often (but not always) reduces resting blood pressure. It has been established that a decrease in blood pressure is associated with a decrease in the tone of the sympathetic system and a drop in systemic vascular resistance.

Increased breathing is an obvious physiological response to exercise.

Rice. 29-2 shows that minute ventilation at the beginning of work increases linearly with increasing work intensity and then, reaching a point near the maximum, becomes superlinear. Thanks to the load, it increases the absorption of oxygen and the production of carbon dioxide by working muscles. Adaptation of the respiratory system consists of extremely precise maintenance of the homeostasis of these gases in the arterial blood. During light to moderate work, arterial Po 2 (and hence oxygen content), Pco 2 and pH remain unchanged at rest. The respiratory muscles involved in increasing ventilation and, above all, in increasing the tidal volume, do not create a feeling of shortness of breath. With a more intense load, already halfway from rest to maximum dynamic work, lactic acid, which is formed in working muscles, begins to appear in the blood. This is observed when lactic acid is formed faster than it is (removed) metabolized-

Rice. 29-2. Dependence of minute ventilation on the intensity of physical activity.

Xia. This point, which depends on the type of work and the state of training of the subject, is called anaerobic or lactate threshold. The lactate threshold for a particular person doing a particular job is relatively constant. The higher the lactate threshold, the higher the intensity of prolonged work. The concentration of lactic acid gradually increases with the intensity of work. At the same time, more and more muscle fibers switch to anaerobic metabolism. Almost completely dissociated lactic acid causes metabolic acidosis. During operation, healthy lungs respond to acidosis by further increasing ventilation, decreasing arterial PCO 2 levels, and maintaining arterial pH at normal levels. This response to acidosis, which promotes nonlinear ventilation of the lungs, can occur during strenuous work (see Fig. 29-2). Within certain operating limits, the respiratory system fully compensates for the decrease in pH caused by lactic acid. However, during the heaviest work, ventilation compensation becomes only partial. In this case, both pH and arterial PCO 2 may fall below baseline levels. The volume of inhalation continues to increase until the stretch receptors limit it.

The control mechanisms of pulmonary ventilation that ensure muscle work include neurogenic and humoral influences. The frequency and depth of breathing are controlled by the respiratory center of the medulla oblongata, which receives signals from central and peripheral receptors that respond to changes in pH, arterial Po 2 and Pto 2. In addition to signals from chemoreceptors, the respiratory center receives afferent impulses from peripheral receptors, including muscle spindles, Golgi stretch receptors, and pressure receptors located in the joints. Central chemoreceptors perceive an increase in alkalinity with intensification of muscle work, which indicates the permeability of the blood-brain barrier to CO 2, but not to hydrogen ions.

Training does not change the magnitude of the respiratory system functions

The impact of training on the respiratory system is minimal. Diffusion capacity of the lungs, their mechanics and even pulmonary

volumes change very little during training. The widespread assumption that exercise improves vital capacity is incorrect: even exercise designed specifically to increase respiratory muscle strength only increases vital capacity by 3%. One of the mechanisms by which the respiratory muscles adapt to physical activity is to reduce their sensitivity to shortness of breath during exercise. However, the primary respiratory changes during exercise are secondary to decreased lactic acid production, which reduces the need for ventilation during strenuous work.

Reactions of muscles and bones to physical activity

The processes that occur during skeletal muscle activity are the primary factor in its fatigue. The same processes, repeated during training, promote adaptation, due to which the volume of work is increased and the development of fatigue during such work is delayed. Skeletal muscle contractions also increase stress on bones, causing specific bone adaptations.

Muscle fatigue is not affected by lactic acid

Historically, it was believed that an increase in intracellular H+ (a decrease in cellular pH) played a major role in muscle fatigue by directly inhibiting actin-myosin bridges and thereby leading to a decrease in contractile force. Although very hard work can reduce the pH value< 6,8 (pH артериальной крови может падать до 7,2), имеющиеся данные свидетельствуют, что повышенное содержание H+ хотя и является значительным фактором в снижении мышечной силы, но не служит исключительной причиной утомления. У здоровых людей утомление коррелирует с накоплением АДФ на фоне нормального или слегка редуцированного содержания АТФ. В этом случае соотношение АДФ/АТФ бывает высоким. Поскольку полное окисление глюкозы, гликогена или свободных жирных кислот до CO 2 и H 2 O является основным источником энергии при продолжительной работе, у людей с нарушениями гликолиза или электронного транспорта снижена способность к продолжительной

work. Potential factors in the development of fatigue can occur centrally (pain signals from a tired muscle feedback to the brain and reduce motivation and possibly reduce impulses from the motor cortex) or at the level of a motor neuron or neuromuscular junction.

Endurance training increases the oxygen capacity of muscles

Skeletal muscle adaptation to training is specific to the form of muscle contraction. Regular exercise under light load conditions increases oxidative metabolic capacity without muscle hypertrophy. Strength training causes muscle hypertrophy. Increased activity without overload increases the density of capillaries and mitochondria, the concentration of myoglobin and the entire enzymatic apparatus for energy production. Coordination of the energy-producing and energy-using systems in muscle is maintained even after atrophy when the remaining contractile proteins are adequately maintained metabolically. Local adaptation of skeletal muscle to long-term work reduces dependence on carbohydrates as energy fuel and allows greater use of fat metabolism, prolongs endurance and reduces the accumulation of lactic acid. A decrease in lactic acid content in the blood, in turn, reduces ventilation dependence on the severity of work. As a result of the slower accumulation of metabolites inside the trained muscle, the chemosensory flow of impulses in the feedback system in the central nervous system decreases with increasing load. This weakens the activation of the sympathetic system of the heart and blood vessels and reduces the myocardial oxygen demand at a fixed level of work.

Muscle hypertrophy in response to stretch

Common forms of physical activity involve a combination of muscle contractions that shorten (concentric contraction), lengthen the muscle (eccentric contraction), and do not change its length (isometric contraction). When exposed to external forces that stretch a muscle, less ATP is required to develop force, since some of the motor units

turned off from work. However, since the forces exerted on individual motor units are greater during eccentric work, eccentric contractions can easily cause muscle damage. This manifests itself in muscle weakness (occurs on the first day), pain, swelling (lasts 1-3 days) and an increase in the level of intramuscular enzymes in plasma (2-6 days). Histological evidence of damage may persist for up to 2 weeks. The damage is accompanied by an acute phase reaction, which includes activation of complement, an increase in circulating cytokines, and the mobilization of neurotrophils and monocytes. If adaptation to training with stretching elements is sufficient, then pain after repeated training is minimal or absent altogether. The damage caused by stretching training and the complex responses to it are most likely the most important stimulus for muscle hypertrophy. The immediate changes in actin and myosin synthesis that cause hypertrophy are mediated at the posttranslational level; a week after the load, the messenger RNA for these proteins changes. Although their exact role remains unclear, the activity of S6 protein kinase, which is closely associated with long-term changes in muscle mass, is increased. Cellular mechanisms of hypertrophy include the induction of insulin-like growth factor I and other proteins belonging to the fibroblast growth factor family.

The contraction of skeletal muscles through the tendons has an effect on the bones. Because bone architecture is altered by load- and stress-removal-induced activation of osteoblasts and osteoclasts, physical activity has significant specific effects on bone mineral density and bone geometry. Repetitive physical activity can create unusually high tension, leading to insufficient bone restructuring and bone fracture; on the other hand, low activity causes osteoclast dominance and bone loss. The forces exerted on bone during exercise depend on bone mass and muscle strength. Therefore, bone density has a lot to do with the forces of gravity and the strength of the muscles involved. This assumes that the load for the purpose

prevent or mitigate osteoporosis must take into account the mass and strength of the activity being applied. Because exercise can improve gait, balance, coordination, proprioception and reaction time even in older and frail people, consistent activity reduces the risk of falls and osteoporosis. In fact, the incidence of hip fractures is reduced by approximately 50% when older adults engage in regular physical activity. However, even when physical activity is optimal, the genetic role of bone mass is much more important than the role of load. Perhaps 75% of population statistics are related to genetics and 25% are the result of various levels of activity. Exercise also plays a role in treatment osteoarthritis. Controlled clinical trials have shown that appropriate regular exercise reduces joint pain and disability.

Dynamic strenuous work (requiring more than 70% of the maximum O 2 intake) slows down the emptying of the liquid contents of the stomach. The nature of this effect is not clear. However, a single load of varying intensity does not change the secretory function of the stomach, and there is no evidence of the effect of the load on the factors contributing to the development of peptic ulcers. It is known that intense dynamic work can cause gastroesophageal reflux, which impairs esophageal motility. Chronic physical activity increases the rate of gastric emptying and the movement of food masses through the small intestine. These adaptive responses constantly increase energy expenditure, promote faster food processing, and increase appetite. Experiments on animals with a model of hyperphagia show a specific adaptation in the small intestine (increase in the surface of the mucosa, the severity of microvilli, a greater content of enzymes and transporters). The intestinal blood flow slows down in proportion to the intensity of the load, and the sympathetic vasoconstrictor tone increases. At the same time, the absorption of water, electrolytes and glucose slows down. However, these effects are transient and the syndrome of reduced absorption as a consequence of acute or chronic exercise is not observed in healthy people. Physical activity is recommended for faster recovery

formation after surgery on the ileum, with constipation and irritable bowel syndrome. Constant dynamic exercise significantly reduces the risk of colon cancer, possibly because the quantity and frequency of food intake increases and, therefore, the movement of stool through the colon accelerates.

Exercise improves insulin sensitivity

Muscular work suppresses insulin secretion due to increased sympathetic influence on the islet apparatus of the pancreas. During work, despite a sharp decrease in the level of insulin in the blood, increased consumption of glucose by muscles occurs, both insulin-dependent and non-insulin-dependent. Muscle activity mobilizes glucose transporters from intracellular storage sites to the plasma membrane of working muscles. Because muscle activity increases insulin sensitivity in people with type 1 (insulin-dependent) diabetes, less insulin is needed when their muscle activity increases. However, this positive result can be insidious, since work accelerates the development of hypoglycemia and increases the risk of hypoglycemic coma. Regular muscle activity reduces the need for insulin by increasing the sensitivity of insulin receptors. This result is achieved through regular adaptation to smaller loads, and not simply by repeating occasional loads. The effect is quite pronounced after 2-3 days of regular physical training, and it can be lost just as quickly. Consequently, healthy people who lead a physically active lifestyle have significantly higher insulin sensitivity than their sedentary counterparts. Increased sensitivity of insulin receptors and less insulin release after regular physical activity serve as adequate therapy for type 2 diabetes (non-insulin dependent), a disease characterized by high insulin secretion and low insulin receptor sensitivity. In people with type 2 diabetes, even a single episode of physical activity significantly affects the movement of glucose transporters to the plasma membrane in skeletal muscle.

Chapter Summary

Physical activity is a type of activity that involves muscle contractions, flexion and extension movements of joints and has an exceptional effect on various body systems.

The quantitative assessment of dynamic load is determined by the amount of oxygen absorbed during operation.

Excessive oxygen consumption in the first minutes of recovery after work is called oxygen debt.

During muscle activity, blood flow is predominantly directed to the working muscles.

During work, blood pressure, heart rate, stroke volume, and cardiac contractility are increased.

In people accustomed to prolonged rhythmic work, the heart, with normal blood pressure and normal thickness of the wall of the left ventricle, ejects large volumes of blood from the left ventricle.

Long-term dynamic work is associated with an increase in high-density lipoproteins in the blood and a decrease in low-density lipoproteins. In this regard, the ratio of high-density lipoproteins and total cholesterol increases.

Muscle exercise plays a role in the prevention and recovery from certain cardiovascular diseases.

Pulmonary ventilation increases during work in proportion to the need for oxygen and removal of carbon dioxide.

Muscle fatigue is a process caused by the execution of a load, leading to a decrease in its maximum strength and independent of lactic acid.

Regular muscle activity with light loads (endurance training) increases muscle oxygen capacity without muscle hypertrophy. Increased activity under heavy loads causes muscle hypertrophy.

People who lead an active lifestyle have a high chance of not being at risk for developing cardiovascular diseases. Even the lightest exercises are effective: they have a good effect on blood circulation, reduce the level of deposits of cholesterol plaques on the walls of blood vessels, strengthen the heart muscle and maintain the elasticity of blood vessels. If the patient also adheres to a proper diet and at the same time exercises, then this is the best medicine to support the heart and blood vessels in excellent shape.

What kind of physical activity can be used for people at high risk of developing heart disease?

Before starting training, patients of the "risk" group should consult with their doctor in order not to harm their health.

People suffering from the following diseases should avoid strenuous exercise and strenuous exercise:

diabetes;
hypertension;
angina pectoris
coronary heart disease;
heart failure.

What effect does sport have on the heart?

Sports can affect the heart in different ways, both strengthen its muscles and lead to serious diseases. In the presence of cardiovascular pathologies, sometimes manifested in the form of chest pain, it is necessary to consult a cardiologist.
It's no secret that athletes often suffer from heart disease due to influence large physical activity on the heart. That is why they are recommended to also include training in their regime before a serious load. This will serve as a kind of “warm-up” of the heart muscles and balance the pulse. Under no circumstances should you suddenly quit training; your heart is accustomed to moderate loads; if they are no longer exercised, hypertrophy of the heart muscles may occur.

The influence of professions on heart function

Conflicts, stress, and lack of normal rest negatively affect the functioning of the heart. A list of professions that negatively affect the heart was compiled: athletes take first place, politicians second; third - teachers.
Professions can be divided into two groups according to their influence on the work of the most important organ - the heart:

Professions are associated with a low-active lifestyle, physical activity is practically absent.
Working with increased psycho-emotional and physical stress.

To strengthen our main organ, it is not necessary to visit all kinds of gyms, it is enough to simply lead an active lifestyle: do housework, often walk in the fresh air, do yoga or light physical exercise.

Ticket 2

Ventricular systole of the heart, its periods and phases. The position of the valves and the pressure in the cavities of the heart during systole.

Ventricular systole- the period of contraction of the ventricles, which allows blood to be pushed into the arterial bed.

Several periods and phases can be distinguished in the contraction of the ventricles:

· Voltage period- characterized by the beginning of a contraction of the muscle mass of the ventricles without changing the volume of blood inside them.

· Asynchronous reduction- the beginning of excitation of the ventricular myocardium, when only individual fibers are involved. The change in ventricular pressure is sufficient to close the atrioventricular valves at the end of this phase.

· Isovolumetric contraction- almost the entire myocardium of the ventricles is involved, but there is no change in the volume of blood inside them, since the efferent (semilunar - aortic and pulmonary) valves are closed. Term isometric contraction is not entirely accurate, since at this time there is a change in the shape (remodeling) of the ventricles and tension of the chordae.

· Exile period- characterized by the expulsion of blood from the ventricles.

· Quick expulsion- the period from the moment the semilunar valves open until systolic pressure is reached in the ventricular cavity - during this period the maximum amount of blood is ejected.

· Slow expulsion- the period when the pressure in the ventricular cavity begins to decrease, but is still higher than the diastolic pressure. At this time, the blood from the ventricles continues to move under the influence of the kinetic energy imparted to it, until the pressure in the cavity of the ventricles and efferent vessels equalizes.

In a state of calm, the ventricle of an adult’s heart pumps out 60 ml of blood (stroke volume) for each systole. The cardiac cycle lasts up to 1 s, respectively, the heart makes 60 contractions per minute (heart rate, heart rate). It is easy to calculate that even at rest, the heart pumps 4 liters of blood per minute (cardiac minute volume, MCV). During maximum exercise, the stroke volume of a trained person’s heart can exceed 200 ml, the pulse can exceed 200 beats per minute, and blood circulation can reach 40 liters per minute. During subsequent ventricular systole the pressure in them becomes higher than the pressure in the atria (which begin to relax), which leads to the closure of the atrioventricular valves. The external manifestation of this event is the first heart sound. The pressure in the ventricle then exceeds the aortic pressure, causing the aortic valve to open and expulsion of blood from the ventricle into the arterial system.

2. Centrifugal nerves of the heart, the nature of the influences coming through them on the activity of the heart. concept of the tone of the vagus nerve nucleus.

The activity of the heart is regulated by two pairs of nerves: vagus and sympathetic. The vagus nerves originate in the medulla oblongata, and the sympathetic nerves arise from the cervical sympathetic ganglion. The vagus nerves inhibit cardiac activity. If you start irritating the vagus nerve with an electric current, the heart slows down and even stops. After cessation of irritation of the vagus nerve, heart function is restored. Under the influence of impulses traveling to the heart through the sympathetic nerves, the rhythm of cardiac activity increases and each heart contraction intensifies. At the same time, the systolic, or stroke, blood volume increases. The vagus and sympathetic nerves of the heart usually act in concert: if the excitability of the center of the vagus nerve increases, then the excitability of the center of the sympathetic nerve decreases accordingly.

During sleep, in a state of physical rest of the body, the heart slows down its rhythm due to an increase in the influence of the vagus nerve and a slight decrease in the influence of the sympathetic nerve. During physical work, the heart rate increases. In this case, the influence of the sympathetic nerve increases and the influence of the vagus nerve on the heart decreases. In this way, an economical mode of operation of the heart muscle is ensured.

Changes in the lumen of blood vessels occur under the influence of impulses transmitted to the walls of blood vessels via vasoconstrictor nerves. The impulses coming through these nerves arise in the medulla oblongata in vasomotor center. An increase in blood pressure in the aorta causes stretching of its walls and, as a result, irritation of the pressoreceptors of the aortic reflexogenic zone. The excitation that arises in the receptors along the fibers of the aortic nerve reaches the medulla oblongata. The tone of the vagus nerve nuclei reflexively increases, which leads to inhibition of cardiac activity, as a result of which the frequency and strength of heart contractions decrease. The tone of the vasoconstrictor center decreases, which causes dilation of the blood vessels of the internal organs. Inhibition of the heart and expansion of the lumen of blood vessels restore the increased blood pressure to normal values.

3. The concept of general peripheral resistance, hemodynamic factors that determine its value.

It is expressed by the equation R = 8*L*nu\n*r4, where L is the length of the vascular bed, nu – viscosity is determined by the ratio of plasma volumes and formed elements, the protein content in plasma and other factors. The least constant of these parameters is the radius of the vessels, and its change in any part of the system can affect the value of the OPS quite significantly. If resistance decreases in some limited region - in a small muscle group or organ, then this may not affect the OPS, but it noticeably changes the blood flow in this particular region, because organ blood flow is also determined by the above formula Q = (Pn-Pk)\R, where Pn can be considered as the pressure in the artery supplying the given organ, Pk is the pressure of the blood flowing through the vein, R is the resistance of all vessels in a given region. As a person ages, the total vascular resistance gradually increases. This is due to an age-related decrease in the number of elastic fibers, an increase in the concentration of ash substances, and a limitation in the distensibility of blood vessels that pass through the “path from fresh grass to hay” throughout life.

No. 4. The renal-adrenal system regulates vascular tone.

The system for regulating vascular tone is activated during orthostatic reactions, blood loss, muscle stress and other conditions in which the activity of the sympathetic nervous system increases. The system includes the JGA of the kidneys, the zona glomerulosa of the adrenal glands, the hormones secreted by these structures and those tissues where their activation occurs. Under the above conditions, the secretion of renin increases, which converts plasma anhytensinogen into angiotensin-1, the latter in the lungs turns into a more active form of angiotensin-2, which is 40 times superior to NA in its vasoconstrictor effect, but has little effect on the vessels of the brain and skeletal muscles and hearts. Angiotensin also has a stimulating effect on the zona glomerulosa of the adrenal glands, promoting the secretion of aldosterone.

Ticket3

1. The concept of eu, hypo, hyperkinetic types of hemodynamics.

The most characteristic feature of type I, first described by V.I. Kuznetsov, is isolated systolic hypertension, caused, as it turns out during the study, by a combination of two factors: an increase in cardiac output and an increase in the elastic resistance of large arteries of the muscular type. The latter symptom is probably associated with excessive tonic tension of the smooth muscle cells of the arteries. However, there is no spasm of arterioles, peripheral resistance is reduced to such an extent that the effect of cardiac output on average hemodynamic pressure is leveled out.

In hemodynamic type II, which occurs in 50–60% of young people with borderline hypertension, the increase in cardiac output and stroke volume is not compensated by adequate expansion of resistive vessels. The discrepancy between cardiac output and peripheral resistance leads to an increase in mean hemodynamic pressure. It is especially significant that in these patients the peripheral resistance remains higher than in the control group, even when the differences in cardiac output disappear.

Finally, hemodynamic type III, which we found in 25-30% of young people, is characterized by an increase in peripheral resistance with a normal cardiac output. We have well-traced observations showing that, at least in some patients, the normally kinetic type of hypertension is formed from the very beginning without a previous phase of hyperkinetic circulation. True, in some of these patients, in response to the load, a pronounced reaction of the hyperkinetic type is observed, that is, there is a high readiness to mobilize cardiac output.

2. Intracardial fur. Regulation of the heart. The relationship between intracardiac and extracardiac regulation mechanisms.

It has also been proven that intracardial regulation provides a hemodynamic connection between the left and right parts of the heart. Its significance lies in the fact that if a large amount of blood enters the right part of the heart during physical activity, then the left part prepares in advance to receive it by increasing active diastolic relaxation, which is accompanied by an increase in the initial volume of the ventricles. Let's consider intracardial regulation using examples. Let’s say that due to an increase in the load on the heart, blood flow to the atria increases, which is accompanied by an increase in the frequency of heart contraction. The reflex arc diagram of this reflex is as follows: the flow of a large amount of blood into the atria is perceived by the corresponding mechanoreceptors (volumoreceptors), information from which is transmitted to the cells of the leading node, in the area of which the mediator norepinephrine is released. Under the influence of the latter, depolarization of the pacemaker cells develops. Therefore, the development time of slow diastolic spontaneous depolarization is shortened. Therefore, the heart rate increases.

If significantly less blood flows to the heart, then the receptor effect from the mechanoreceptors turns on the cholinergic system. As a result, the mediator acetylcholine is released in the cells of the sinoatrial node, causing hyperpolarization of atypical fibers. As a result, the development time of slow spontaneous diastolic depolarization increases, and heart rate, accordingly, decreases.

If the blood flow to the heart increases, then not only the heart rate increases, but also the systolic output due to intracardial regulation. What is the mechanism for increasing the force of heart contractions? It is presented as follows. Information at this stage comes from the mechanoreceptors of the atria to the contractile elements of the ventricles, apparently through interneurons. So, if blood flow to the heart increases during physical activity, this is perceived by the mechanoreceptors of the atria, which turns on the adrenergic system. As a result, norepinephrine is released at the corresponding synapses, which, through (most likely) the calcium (possibly cAMP, cGMP) cellular regulation system, causes an increased release of calcium ions to the contractile elements, increasing the coupling of muscle fibers. It is also possible that norepinephrine reduces the resistance in the nexuses of reserve cardiomyocytes and connects additional muscle fibers, due to which the strength of heart contractions also increases. If blood flow to the heart decreases, the cholinergic system is activated through the mechanoreceptors of the atria. As a result of this, the mediator acetylcholine is released, which inhibits the release of calcium ions into the interfibrillar space, and the conjugation weakens. It can also be assumed that under the influence of this mediator, the resistance in the nexuses of working motor units increases, which is accompanied by a weakening of the contractile effect.

3. Systemic blood pressure, its fluctuations depending on the phase of the cardiac cycle, gender, age and other factors. Blood pressure in various parts of the circulatory system.

Systemic blood pressure in the initial parts of the circulatory system - in large arteries. its value depends on changes occurring in any part of the system. The value of systemic blood pressure depends on the phase of the cardiac cycle. The main hemodynamic factors influencing the value of systemic blood pressure are determined from the given formula:

P=Q*R(r,l,nu). Q-intensity and heart rate, venous tone. R-tone of arterial vessels, elastic properties and thickness of the vascular wall.

Blood pressure also changes due to the phases of breathing: during inspiration it decreases. Blood pressure is a relatively mild statement: its value can fluctuate throughout the day: during physical work of greater intensity, systolic pressure can increase by 1.5-2 times. It also increases with emotional and other types of stress. The highest values of systemic blood pressure under resting conditions are recorded in the morning; for many people, its second peak appears at 15-18 hours. Under normal conditions, a healthy person’s blood pressure fluctuates during the day by no more than 20-25 mmHg. With age, systolic blood pressure gradually increases - at 50-60 years old to 139 mmHg, while diastolic pressure also increases slightly. Question about normal blood pressure values are extremely important, because high blood pressure among people over 50 years of age occurs in 30%, and among women in 50% of those examined. At the same time, not everyone makes any complaints, despite the increasing danger of complications.

4. Vasoconstrictor and vasodilator nerve effects. The mechanism of their action on vascular tone.

In addition to local vasodilatory mechanisms, skeletal muscles are supplied by sympathetic vasoconstrictor nerves and also (in some animal species) by sympathetic vasodilator nerves. Sympathetic vasoconstrictor nerves. The mediator of the sympathetic vasoconstrictor nerves is norepinephrine. Maximum activation of sympathetic adrenergic nerves leads to a decrease in blood flow in the vessels of skeletal muscles by 2 and even 3 times compared to the resting level. This reaction has important physiological significance in the development of circulatory shock and in other cases when it is vital to maintain normal or even high levels of systemic blood pressure. In addition to norepinephrine, secreted by the endings of the sympathetic vasoconstrictor nerves, large amounts of norepinephrine and epinephrine are released into the bloodstream by adrenal medulla cells, especially during heavy physical activity. Norepinephrine circulating in the blood has the same vasoconstrictor effect on the vessels of skeletal muscles as the mediator of the sympathetic nerves. However, adrenaline most often causes moderate dilation of muscle vessels. The fact is that adrenaline interacts mainly with beta-adrenergic receptors, the activation of which leads to vasodilation, while norepinephrine interacts with alpha-adrenergic receptors and always causes vasoconstriction. Three main mechanisms contribute to the sharp increase in blood flow in skeletal muscles during exercise: (1) excitation of the sympathetic nervous system, causing general changes in the circulatory system; (2) increased blood pressure; (3) increased cardiac output.

Sympathetic vasodilator system. The influence of the central nervous system on the sympathetic vasodilator system. The sympathetic nerves of skeletal muscles, along with vasoconstrictor fibers, contain sympathetic vasodilator fibers. In some mammals, such as cats, these vasodilator fibers release acetylcholine (rather than norepinephrine). In primates, adrenaline is believed to have a vasodilatory effect by interacting with beta-adrenergic receptors in skeletal muscle vessels. Descending pathways through which the central nervous system controls vasodilatory influences. The main area of the brain that exercises this control is the anterior hypothalamus. The sympathetic vasodilator system may not have much functional significance. It is doubtful that the sympathetic vasodilator system plays a significant role in the regulation of blood circulation in humans. Complete blockade of the sympathetic nerves of skeletal muscles has virtually no effect on the ability of these tissues to self-regulate blood flow depending on metabolic needs. On the other hand, experimental studies show that at the very beginning of physical activity, it is the sympathetic vasodilation of skeletal muscles that possibly leads to an outstripping increase in blood flow even before the need for oxygen and nutrients in skeletal muscles increases.

Ticket

1. heart sounds, their origin. Principles of phonocardiography and advantages of this method over auscultation.

Heart sounds- a sound manifestation of the mechanical activity of the heart, determined by auscultation as alternating short (percussive) sounds that are in a certain connection with the phases of the systole and diastole of the heart. T.s. are formed in connection with the movements of the valves of the heart, chords, heart muscle and vascular wall, generating sound vibrations. The auscultated loudness of tones is determined by the amplitude and frequency of these oscillations (see. Auscultation). Graphic registration of T.s. using phonocardiography showed that, in its physical essence, T. s. are noises, and their perception as tones is due to the short duration and rapid attenuation of aperiodic oscillations.

Most researchers distinguish 4 normal (physiological) T. s., of which I and II tones are always heard, and III and IV are not always determined, more often graphically than during auscultation ( rice. ).

The first sound is heard as a fairly intense sound over the entire surface of the heart. It is maximally expressed in the region of the apex of the heart and in the projection of the mitral valve. The main fluctuations of the first tone are associated with the closure of the atrioventricular valves; participate in its formation and movements of other structures of the heart.

The second sound is also heard over the entire region of the heart, maximally at the base of the heart: in the second intercostal space to the right and left of the sternum, where its intensity is greater than the first tone. The origin of the second sound is mainly associated with the closure of the aortic valves and pulmonary trunk. It also includes low-amplitude, low-frequency oscillations resulting from the opening of the mitral and tricuspid valves. On FCG, the first (aortic) and second (pulmonary) components are distinguished as part of the second tone

Ill tone - low frequency - is perceived during auscultation as a weak, dull sound. On FCG it is determined on the low-frequency channel, more often in children and athletes. In most cases, it is recorded at the apex of the heart, and its origin is associated with vibrations of the muscular wall of the ventricles due to their stretching at the time of rapid diastolic filling. Phonocardiographically, in some cases, left and right ventricular III sounds are distinguished. The interval between II and left ventricular tone is 0.12-15 With. The so-called opening tone of the mitral valve is distinguished from the third tone - a pathognomonic sign of mitral stenosis. The presence of a second tone creates an auscultatory picture of the “quail rhythm”. Pathological III tone appears when heart failure and determines the proto- or mesodiastolic gallop rhythm (see. gallop rhythm). Ill tone is best heard with the stethoscope head of a stethoscope or by direct auscultation of the heart with the ear tightly attached to the chest wall.

IV tone - atrial - is associated with contraction of the atria. When recording synchronously with an ECG, it is recorded at the end of the P wave. This is a weak, rarely heard tone, recorded on the low-frequency channel of the phonocardiograph mainly in children and athletes. A pathologically enhanced IV tone causes a presystolic gallop rhythm during auscultation. The fusion of III and IV pathological tones during tachycardia is defined as a “summation gallop.”

Phonocardiography is one of the methods for diagnostic examination of the heart. It is based on the graphical recording of sounds accompanying heart contractions using a microphone that converts sound vibrations into electrical vibrations, an amplifier, a frequency filter system and a recording device. Mainly heart sounds and murmurs are recorded. The resulting graphic image is called a phonocardiogram. Phonocardiography significantly complements auscultation and makes it possible to objectively determine the frequency, shape and duration of recorded sounds, as well as their changes in the process of dynamic observation of the patient. Phonocardiography is used mainly for the diagnosis of heart defects and phase analysis of the cardiac cycle. This is especially important in case of tachycardia, arrhythmias, when with the help of auscultation alone it is difficult to decide in which phase of the cardiac cycle certain sound phenomena occurred.

The harmlessness and simplicity of the method make it possible to carry out research even on a patient in serious condition, and with the frequency necessary to solve diagnostic problems. In departments of functional diagnostics, for carrying out phonocardiography, a room with good sound insulation is allocated, in which the temperature is maintained at 22-26 ° C, since at a lower temperature the subject may experience muscle tremors, distorting the phonocardiogram. The study is carried out with the patient in a supine position, holding his breath in the exhalation phase. The analysis of phonocardiography and the diagnostic conclusion on it is carried out only by a specialist, taking into account auscultatory data. To correctly interpret phonocardiography, synchronous recording of a phonocardiogram and an electrocardiogram is used.

Auscultation is the process of listening to sound phenomena occurring in the body.

Usually these phenomena are weak and direct and mediocre auscultation is used to detect them; The first is called listening with the ear, and the second is listening with the help of special hearing instruments - a stethoscope and a phonendoscope.

2. Hemodynamic mechanisms of regulation of heart activity. The law of the heart, its meaning.

Hemodynamic, or myogenic, mechanisms of regulation ensure the constancy of the systolic blood volume. The strength of heart contractions depends on its blood supply, i.e. on the initial length of muscle fibers and the degree of their stretch during diastole. The more stretched the fibers, the greater the blood flow to the heart, which leads to an increase in the strength of heart contractions during systole - this is the "law of the heart" (Frank-Starling's law). This type of hemodynamic regulation is called heterometric.

It is explained by the ability of Ca2 + to leave the sarcoplasmic reticulum. The more the sarcomere is stretched, the more Ca2+ is released and the greater the force of contractions of the heart. This self-regulation mechanism is activated when the body position changes, with a sharp increase in the volume of circulating blood (during transfusion), as well as with pharmacological blockade of the sympathetic nervous system by beta-sympatholytics.

Another type of myogenic self-regulation of heart function - homeometric - does not depend on the initial length of cardiomyocytes. The force of heart contraction may increase as the heart rate increases. The more often it contracts, the higher the amplitude of its contractions (Bowditch’s “ladder”). When the pressure in the aorta increases to certain limits, the counterload on the heart increases, and the force of heart contractions increases (Anrep phenomenon).

Intracardiac peripheral reflexes belong to the third group of regulatory mechanisms. In the heart, regardless of the nervous elements of extracardial origin, the intraorgan nervous system functions, forming miniature reflex arcs, which include afferent neurons, the dendrites of which begin on stretch receptors on the fibers of the myocardium and coronary vessels, intercalary and efferent neurons (Dogel cells I, II and III order), the axons of which can end on myocardiocytes located in another part of the heart.

Thus, an increase in blood flow to the right atrium and stretching of its walls leads to increased contraction of the left ventricle. This reflex can be blocked using, for example, local anesthetics (novocaine) and ganglion blockers (beisohexonium).

The law of the heart Starling's law, the dependence of the energy of contraction of the heart on the degree of stretching of its muscle fibers. The energy of each heart contraction (systole) changes in direct proportion

diastolic volume. The law of the heart established by the English physiologist E. Starling in 1912-18 on cardiopulmonary drug. Starling found that the volume of blood ejected by the heart into the arteries with each systole increases in proportion to the increase in venous return of blood to the heart; the increase in the strength of each contraction is associated with an increase in the volume of blood in the heart by the end of diastole and, as a result, an increase in the stretching of the myocardial fibers. The law of the heart does not determine the entire activity of the heart, but explains one of the mechanisms of its adaptation to the changing conditions of the organism's existence. In particular, The law of the heart underlies the maintenance of a relative constancy of stroke volume with an increase in vascular resistance in the arterial part of the cardiovascular system. This self-regulating mechanism, due to the properties of the heart muscle, is inherent not only in an isolated heart, but also participates in the regulation of the activity of the cardiovascular system in the body; controlled by nervous and humoral influences

3. Volumetric blood flow velocity, its value in different parts of the sss. Hemodynamic factors that determine its value.

Q-volume velocity of blood flow is the amount of blood flowing through the cross section of the system per unit time. This total value is the same in all sections of the system. Blood circulation, if we consider it as a whole. THOSE. the amount of blood ejected from the heart per minute is equal to the amount of blood returning to it and passing through the total cross-section of the circulatory circle in any part of it during the same time. Volumetric blood flow is distributed unevenly in the vascular system and depends on a) the degree of “privilege” of the organ , B) from the functional load on it. The brain and heart receive significantly more blood (15 and 5 at rest; 4 and 5 during physical activity), liver and gastrointestinal tract (20 and 4); muscles (20 and 85); bones, bone marrow, adipose tissue (15 and 2) . Functional hyperpia is achieved by many mechanisms. Under the influence of chemical, humoral, and nervous influences in the working organ, vasodilation occurs, the resistance to blood flow in them decreases, which leads to the redistribution of blood and, in conditions of constant blood pressure, can cause a deterioration in the blood supply to the heart, liver and other organs. . In conditions of physical Under load, systemic blood pressure increases, sometimes quite significantly (up to 180-200), which prevents a decrease in blood flow in the internal organs and ensures an increase in blood flow in the working organ. Hemodynamically can be expressed by the formula Q=P*n*r4/8*nu*L

4. the concept of acute, Q-volume velocity of blood flow is the amount of blood flowing through the cross-section of the system per unit time. This total value is the same in all sections of the system. Blood circulation, if we consider it as a whole. THOSE. the amount of blood ejected from the heart per minute is equal to the amount of blood returning to it and passing through the total cross-section of the circulatory circle in any part of it during the same time. Volumetric blood flow is distributed unevenly in the vascular system and depends on a) the degree of “privilege” of the organ , B) from the functional load on it. The brain and heart receive significantly more blood (15 and 5 at rest; 4 and 5 during physical activity), liver and gastrointestinal tract (20 and 4); muscles (20 and 85); bones, bone marrow, adipose tissue (15 and 2) . Functional hyperpia is achieved by many mechanisms. Under the influence of chemical, humoral, and nervous influences in the working organ, vasodilation occurs, the resistance to blood flow in them decreases, which leads to the redistribution of blood and, in conditions of constant blood pressure, can cause a deterioration in the blood supply to the heart, liver and other organs. . In conditions of physical Under load, systemic blood pressure increases, sometimes quite significantly (up to 180-200), which prevents a decrease in blood flow in the internal organs and ensures an increase in blood flow in the working organ. Hemodynamically can be expressed by the formula Q=P*n*r4/8*nu*L

4. The concept of acute, subacute, chronic regulation of blood pressure.

Acute-nervoreflex mechanism initiated by baroreceptors of blood vessels. The baroreceptors of the aortic and carotid zones have the most powerful influence on the depressor zone of the hemodynamic center. applying a plaster bandage to such an area as a sleeve eliminates the excitation of baroreceptors, so it was concluded that they respond not to the pressure itself, but to the stretching of the vessel wall under the influence of blood pressure. This is also facilitated by the structural features of the areas of the vessels where there are baroreceptors: they are thinned, they have few muscles and many elastic fibers. The depressor effects of baroreceptors are also used in practical medicine: pressing on the neck in the region. projections of the carotid artery can help stop an attack of tachycardia, and transcutaneous irritation in the carotid zone is used to reduce blood pressure. On the other hand, adaptation of baroreceptors as a result of a prolonged increase in blood pressure, as well as the development of sclerotic changes in the walls of blood vessels and a decrease in their distensibility can become factors contributing to the development of hypertension. Transection of the depressor nerve in dogs produces this effect in a relatively short time. In rabbits, transection of the nerve starting in the aortic zone, the receptors of which are more active with significant increases in blood pressure, causes death from a sharp increase in blood pressure and disturbances in cerebral blood flow. To maintain the stability of the blood pressure, the baroreceptors of the heart itself are even more important than the vascular ones. Novocainization of epicardial receptors can lead to the development of hypertension. Baroreceptors of the brain change their activity only during terminal states of the body. Baroreceptor reflexes are suppressed by the action of nociceptive ones, in particular those associated with disturbances of coronary blood flow, as well as by activation of chemoreceptors, emotional stress and physical activity. One of the mechanisms of reflex suppression during physical. The load is an increase in the venous return of blood to the heart, as well as the implementation of the Bainbridge unloading reflex and heterometric regulation.

Subacute regulation - blood pressure includes hemodynamic mechanisms realized through changes in blood volume. in decapitated animals with a destroyed spinal cord, 30 minutes after blood loss or injection of fluid into the vessels in a volume of 30% of the blood volume, blood pressure is restored to a level close to a similar one. These mechanisms include: 1) changes in the movement of fluid from capillaries to tissues and vice versa; 2) changes in blood deposition in the venous section; 3) changes in renal filtration and reabsorption (an increase in blood pressure by just 5 mm Hg, other things being equal, can cause diuresis)

Chronic regulation of blood pressure is ensured by the renal-adrenal system, the elements of which and the nature of their influence on each other are reflected in the diagram, where positive effects are marked by arrows with a + sign, and negative ones -

Ticket

1. Diastole of the ventricles of the heart, its periods and phases. valve position and pressure in the cavities of the heart during diastole.

By the end of ventricular systole and the beginning of diastole (from the moment the semilunar valves close), the ventricles contain a residual, or reserve, volume of blood (end-systolic volume). At the same time, a sharp drop in pressure in the ventricles begins (the phase of isovolumic, or isometric, relaxation). The ability of the myocardium to quickly relax is the most important condition for filling the heart with blood. When the pressure in the ventricles (initial diastolic) becomes less than the pressure in the atria, the atrioventricular valves open and the rapid filling phase begins, during which blood accelerates from the atria to the ventricles. During this phase, up to 85% of their diastolic volume enters the ventricles. As the ventricles fill, the rate at which they fill with blood decreases (slow filling phase). At the end of ventricular diastole, atrial systole begins, as a result of which another 15% of their diastolic volume enters the ventricles. Thus, at the end of diastole, an end-diastolic volume is created in the ventricles, which corresponds to a certain level of end-diastolic pressure in the ventricles. End-diastolic volume and end-diastolic pressure constitute the so-called preload of the heart, which is the determining condition for the stretching of myocardial fibers, i.e., the implementation of the Frank-Starling law.

2. Cardiovascular center, its localization. Structural and functional features.

Vasomotor center

V.F. Ovsyannikov (1871) established that the nerve center that provides a certain degree of narrowing of the arterial bed - the vasomotor center - is located in the medulla oblongata. The localization of this center was determined by cutting the brain stem at different levels. If the transection is performed in a dog or cat above the quadrigeminal area, then blood pressure does not change. If the brain is cut between the medulla oblongata and the spinal cord, the maximum blood pressure in the carotid artery decreases to 60-70 mm Hg. It follows that the vasomotor center is localized in the medulla oblongata and is in a state of tonic activity, i.e., long-term constant excitation. Elimination of its influence causes vasodilatation and a drop in blood pressure.

A more detailed analysis showed that the vasomotor center of the medulla oblongata is located at the bottom of the IV ventricle and consists of two sections - pressor and depressor. Irritation of the pressor part of the vasomotor center causes a narrowing of the arteries and a rise, and irritation of the second part causes the dilation of the arteries and a drop in blood pressure.

It is believed that the depressor section of the vasomotor center causes vasodilation, lowering the tone of the pressor section and thus reducing the effect of the vasoconstrictor nerves.

Influences coming from the vasoconstrictor center of the medulla oblongata come to the nerve centers of the sympathetic part of the autonomic nervous system, located in the lateral horns of the thoracic segments of the spinal cord, which regulate vascular tone in individual parts of the body. Spinal centers are capable, some time after turning off the vasoconstrictor center of the medulla oblongata, to slightly increase blood pressure, which has decreased due to the expansion of arteries and arterioles. In addition to the vasomotor centers of the medulla oblongata and spinal cord, the condition of the vessels is influenced by the nerve centers of the diencephalon and cerebral hemispheres.

3.Functional classification of blood vessels.

Shock-absorbing vessels - aorta, pulmonary artery and their large branches, i.e. elastic vessels.

Distribution vessels are medium and small arteries of the muscular type of regions and organs. their function is to distribute blood flow throughout all organs and tissues of the body. As tissue demand increases, the diameter of the vessel adjusts to the increased blood flow in accordance with the change in linear velocity due to an endothelium-dependent mechanism. With an increase in shear stress (the frictional force between the layers of blood and the endothelium of the vessel, preventing the movement of blood.) of the parietal layer of blood, the apical membrane of endothelial cells is deformed, and they synthesize vasodilators (nitric oxide), which reduce the tone of the smooth muscles of the vessel, i.e. the vessel dilates. If this mechanism is disrupted, the distribution vessels can become a limiting link that prevents a significant increase in blood flow in the organ, despite its metabolic demand, for example, coronary and cerebral vessels affected by atherosclerosis.

Resistance vessels - artery with a diameter of less than 100 μm, arterioles, precapillary sphincters, sphincters of the main capillaries. These vessels account for about 60% of the total resistance to blood flow, hence their name. They regulate blood flow at the systemic, regional and microcirculatory levels. The total resistance of blood vessels in different regions forms systemic diastolic blood pressure, changes it and maintains it at a certain level as a result of general neurogenic and humoral changes in the tone of these vessels. Multidirectional changes in the tone of resistance vessels of different regions ensure redistribution of volumetric blood flow between regions. In a region or organ, they redistribute blood flow between microregions, that is, they control microcirculation. Resistance vessels of a microregion distribute blood flow between the exchange and shunt circuits, determining the number of functioning capillaries.

Exchange vessels are capillaries. Partial transport of substances from the blood to the tissues also occurs in arterioles and venules. Oxygen easily diffuses through the wall of arterioles, and through the hatches of the venules, protein molecules diffusion from the blood, which subsequently enter the lymph. Water, water-soluble inorganic and low-molecular organic substances (ions, glucose, ureas) pass through the pores. In some organs (skeletal muscles, skin, lungs, central nervous system) the capillary wall is a barrier (histo-hematic, hemato-encephalic). In the mucous membrane of the gastrointestinal tract, kidneys, internal glands. And external Secretion capillaries have fenestrae (20-40 nm) that ensure the activity of these organs.

Shunt Vessels - Shunt vessels are arteriovenous anastomoses that are present in some tissues. When these vessels are open, blood flow through the capillaries either decreases or stops completely. Most typical of the skin: if it is necessary to reduce heat transfer, blood flow through the capillary system stops and blood is shunted from the arterial system to the venous system.

Capacitive (accumulating) vessels - in which changes in the lumen, even so small that they do not have a significant effect on the overall resistance, cause pronounced changes in the distribution of blood and the amount of its inflow to the heart (venous section of the system). These are postcapillary venules, venules, small veins, venous plexuses and specialized formations - splenic sinusoids. Their total capacity is about 50% of the total blood volume contained in the cardiovascular system. The functions of these vessels are associated with the ability to change their capacity, which is due to a number of morphological and functional features of capacitive vessels.

Vessels of blood return to the heart - These are medium, large and hollow veins that act as collectors through which regional outflow of blood and its return to the heart are ensured. The capacity of this section of the venous bed is about 18% and under physiological conditions changes little (less than 1/5 of the original capacity). Veins, especially superficial ones, can increase the volume of blood they contain due to the ability of the walls to stretch when transmural pressure increases.

4. features of hemodynamics in the pulmonary circulation. blood supply to the lungs and its regulation.

Of significant interest for pediatric anesthesiology is the study of hemodynamics of the pulmonary circulation. This is due primarily to the special role of pulmonary hemodynamics in maintaining homeostasis during anesthesia and surgery, as well as its multicomponent dependence on blood loss, cardiac output, methods of artificial ventilation, etc.

In addition, the pressure in the pulmonary arterial bed differs significantly from the pressure in the systemic arteries, which is due to the peculiarity of the morphological structure of the pulmonary vessels

This leads to the fact that the mass of circulating blood in the pulmonary circulation can increase significantly without causing an increase in pressure in the pulmonary artery due to the opening of non-functioning vessels and shunts.

In addition, the pulmonary arterial bed has greater distensibility due to the abundance of elastic fibers in the walls of blood vessels and provides resistance during the operation of the right ventricle 5-6 times less than the resistance that the left ventricle encounters during contraction. Under physiological conditions, pulmonary blood flow through the system pulmonary circulation is equal to the blood flow in the systemic circulation

In this regard, studying the hemodynamics of the pulmonary circulation can provide new interesting information about the complex processes occurring during surgical interventions, especially since this issue remains poorly studied in children.
A number of authors note an increase in pressure in the pulmonary artery and an increase in pulmonary vascular resistance in chronic suppurative lung diseases in children.

It should be noted that hypertension syndrome of the pulmonary circulation develops due to narrowing of the pulmonary arterioles in response to a decrease in oxygen tension in the alveolar air.

Since during operations using artificial lung ventilation, and especially during operations on the lungs, a decrease in oxygen tension in the alveolar air can be observed, the study of pulmonary hemodynamics is of additional interest.

Blood from the right ventricle is directed through the pulmonary artery and its branches into the capillary networks of the respiratory tissue of the lung, where it is enriched with oxygen. Upon completion of this process, blood from the capillary networks is collected by the branches of the pulmonary vein and sent to the left atrium. It should be remembered that in the pulmonary circulation, blood moves through the arteries, which we usually call venous, and arterial blood flows in the veins.
The pulmonary artery enters the root of each lung and branches further along with the bronchial tree, so that each branch of the tree is accompanied by a branch of the pulmonary artery. Small branches reaching the respiratory bronchioles supply blood to the terminal branches, which supply blood to the capillary networks of the alveolar ducts, sacs and alveoli.
Blood from the capillary networks in the respiratory tissue collects in the smallest branches of the pulmonary vein. They begin in the parenchyma of the lobules and here they are surrounded by thin connective tissue membranes. They enter the interlobular septa, where they open into the interlobular veins. The latter, in turn, are directed along the partitions to those areas where the tops of several lobules converge. Here the veins come into close contact with the branches of the bronchial tree. From this place to the root of the lung, the veins go together with the bronchi. In other words, with the exception of the area inside the lobules, the branches of the pulmonary artery and vein follow together with the branches of the bronchial tree; inside the lobules, however, only arteries go along with the bronchioles.
Oxygenated blood is carried to parts of the lung itself by the bronchial arteries. The latter also pass into the lung tissue in close connection with the bronchial tree and feed the capillary networks in its walls. They also supply blood to the lymph nodes scattered throughout the bronchial tree. In addition, the branches of the bronchial arteries run along the interlobular septa and supply oxygenated blood to the capillaries of the visceral layer of the pleura.
Naturally, there are differences between the blood in the arteries of the pulmonary circulation and the arteries of the systemic circulation—both the pressure and the oxygen content in the first are lower than in the second. Therefore, anastomoses between the two circulatory systems in the lung will create unusual physiological problems.

Ticket.

1. Bioelectric phenomena in the heart. Teeth and interval ekg. Properties of the heart muscle assessed by ecg.

2. changes in heart function during physical activity. Fur. And meaning.

Heart function during physical activity

The frequency and strength of heart contractions during muscle work increase significantly. Muscle work while lying down increases the pulse rate less than sitting or standing.

Maximum blood pressure increases to 200 mm Hg. and more. An increase in blood pressure occurs in the first 3-5 minutes from the start of work, and then in strong trained people during prolonged and intense muscular work it remains at a relatively constant level due to the training of reflex self-regulation. In weak and untrained people, blood pressure begins to fall already during work due to lack of training or insufficient training of reflex self-regulation, which leads to loss of ability to work due to a decrease in blood supply to the brain, heart, muscles and other organs.

In people trained for muscular work, the number of heart contractions at rest is less than in untrained people, and, as a rule, no more than 50-60 per minute, and in especially trained people - even 40-42. It can be assumed that this decrease in heart rate is due to the intensity of those involved in physical exercises that develop endurance. With a rare heartbeat rhythm, the duration of the isometric contraction phase and diastole is increased. The duration of the exile phase is almost unchanged.

Resting systolic volume is the same in trained people as in untrained people, but as training increases, it decreases. Consequently, their resting minute volume also decreases. However, in trained people, the systolic volume at rest, like in untrained people, is combined with an increase in the cavities of the ventricles. It should be noted that the ventricular cavity contains: 1) systolic volume, which is released during its contraction, 2) reserve volume, which is used during muscle activity and other conditions associated with increased blood supply, and 3) residual volume, which is almost not used even with the most intense work of the heart. Unlike the untrained, the trained ones have a particularly increased reserve volume, and the systolic and residual volumes are almost the same. The large reserve volume in trained individuals allows one to immediately increase the systolic ejection of blood at the beginning of work. Bradycardia, prolongation of the isometric tension phase, decrease in systolic volume and other changes indicate economical activity of the heart at rest, which is designated as regulated myocardial hypodynamia. During the transition from rest to muscular activity, trained individuals immediately experience cardiac hyperdynamia, which consists of increased heart rate, increased systole, shortening or even disappearance of the isometric contraction phase.

The minute volume of blood increases after exercise, which depends on the increase in systolic volume and the force of heart contraction, the development of the heart muscle and improved nutrition.

During muscular work and in proportion to its size, the minute volume of a person’s heart increases to 25-30 dm 3, and in exceptional cases to 40-50 dm 3. This increase in minute volume occurs (especially in trained people) mainly due to systolic volume, which in humans can reach 200-220 cm 3. A less significant role in increasing cardiac output in adults is played by increased heart rate, which especially increases when systolic volume reaches its limit. The greater the training, the relatively more powerful work a person can perform with an optimal heart rate of up to 170-180 per minute. An increased heart rate above this level makes it difficult for the heart to fill with blood and supply blood through the coronary vessels. With maximum intensity work, a trained person's heart rate can reach 260-280 per minute.

During muscle work, the blood supply to the heart muscle itself increases. If 200-250 cm3 of blood flows per minute through the coronary vessels of the human heart at rest, then during intense muscular work the amount of blood flowing through the coronary vessels reaches 3.0-4.0 dm3 per minute. When blood pressure increases by 50%, 3 times more blood flows through the dilated coronary vessels than at rest. The expansion of the coronary vessels occurs reflexively, as well as due to the accumulation of metabolic products and the entry of adrenaline into the blood.

An increase in blood pressure in the aortic arch and carotid sinus reflexively dilates the coronary vessels. The coronary vessels dilate the fibers of the sympathetic nerves of the heart, excited both by adrenaline and acetylcholine.

In trained people, the mass of the heart increases in direct proportion to the development of their skeletal muscles. In trained men, the heart volume is larger than in untrained men, 100-300 cm 3, and in women - by 100 cm 3 or more.

During muscular work, minute volume increases and blood pressure increases, and therefore the work of the heart is 9.8-24.5 kJ per hour. If a person performs muscular work for 8 hours a day, then the heart produces approximately 196-588 kJ of work during the day. In other words, the heart performs work per day equal to that expended by a person weighing 70 kg when climbing 250-300 meters. Cardiac performance increases with muscular activity not only due to an increase in the volume of systolic ejection and an increase in heart rate, but also due to a greater acceleration of blood circulation, since the rate of systolic ejection increases by 4 times or more.

The acceleration and intensification of the heart and the narrowing of blood vessels during muscular work occurs reflexively due to irritation of the skeletal muscle receptors during their contractions.

3. Arterial pulse, its origin. Sphygmography.

Arterial pulse is the rhythmic oscillation of arterial walls caused by the passage of a pulse wave. A pulse wave is a propagating oscillation of the arterial wall resulting from a systolic increase in blood pressure. A pulse wave occurs in the aorta during systole, when a systolic portion of blood is ejected into it and its wall is stretched. Since the pulse wave moves along the wall of the arteries, the speed of its propagation does not depend on the linear speed of blood flow, but is determined by the morphofunctional state of the vessel. The greater the rigidity of the wall, the greater the speed of propagation of the pulse wave and vice versa. Therefore, in young people it is 7-10 m/sec, and in old people, due to atherosclerotic changes in blood vessels, it increases. The simplest method of studying the arterial pulse is palpation. Typically, the pulse is felt at the radial artery by pressing it against the underlying radius.

The pulse diagnostic method originated many centuries BC. Among the literary sources that have reached us, the most ancient are works of ancient Chinese and Tibetan origin. The ancient Chinese include, for example, “Bin-hu Mo-xue”, “Xiang-lei-shi”, “Zhu-bin-shi”, “Nan-ching”, as well as sections in the treatises “Jia-i-ching”, “Huang-di Nei-ching Su-wen Lin-shu” and others.

The history of pulse diagnosis is inextricably linked with the name of the ancient Chinese healer - Bian Qiao (Qin Yue-Ren). The beginning of the path of the pulse diagnosis technique is associated with one of the legends, according to which Bian Qiao was invited to treat the daughter of a noble mandarin (official). The situation was complicated by the fact that even doctors were strictly forbidden to see and touch persons of noble rank. Bian Qiao asked for thin string. Then he suggested tying the other end of the cord to the wrist of the princess, who was behind the screen, but the court healers disdainfully treated the invited doctor and decided to play a trick on him by tying the end of the cord not to the princess’s wrist, but to the paw of a dog running nearby. A few seconds later, to the surprise of those present, Bian Qiao calmly declared that these were impulses not of a person, but of an animal, and this animal tossed with worms. The skill of the doctor aroused admiration, and the cord was transferred with confidence to the princess's wrist, after which the disease was determined and treatment was prescribed. As a result, the princess quickly recovered, and his technique became widely known.

Sphygmography(Greek sphygmos pulse, pulsation + graphō write, depict) - a method for studying hemodynamics and diagnosing some forms of pathology of the cardiovascular system, based on graphic registration of pulse oscillations in the wall of a blood vessel.

Sphygmography is carried out using special attachments to an electrocardiograph or other registrar, which make it possible to convert the mechanical vibrations of the vessel wall perceived by the pulse receiver (or the accompanying changes in the electrical capacitance or optical properties of the studied area of the body) into electrical signals, which, after preliminary amplification, are fed to the recording device. The recorded curve is called a sphygmogram (SG). There are both contact (applied to the skin over the pulsating artery) and non-contact, or remote, pulse receivers. The latter are usually used to register a venous pulse - phlebosphygmography. Recording pulse oscillations of a limb segment using a pneumatic cuff or strain gauge placed around its perimeter is called volumetric sphygmography.

4.Features of blood pressure regulation in individuals with hypo and hyperkinetic types of blood circulation. The place of hemodynamic and humoral mechanisms in the self-regulation of blood pressure.

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1. minute blood volume and systolic blood volume. Their sizes. Determination methods.

Minute volume of blood circulation characterizes the total amount of blood pumped by the right and left parts of the heart within one minute in the cardiovascular system. The measurement of minute volume of blood circulation is l/min or ml/min. To level out the influence of individual anthropometric differences on the value of the IOC, it is expressed as a cardiac index. The cardiac index is the value of the minute volume of blood circulation divided by the body surface area in m. The dimension of the cardiac index is l/(min m2).

The most accurate method for determining the minute volume of blood flow in humans was proposed by Fick (1870). It consists of an indirect calculation of the IOC, which is carried out knowing the difference between the oxygen content in the arterial and When using the Fick method, it is necessary to take mixed venous blood from the right half of the heart. Venous blood from a person is taken from the right side of the heart using a catheter inserted into the right atrium through the brachial vein. The Fick method, being the most accurate, is not widely used in practice due to its technical complexity and labor intensity (the need for cardiac catheterization, puncture of the artery, determination of gas exchange). venous blood, the volume of oxygen consumed by a person per minute.

By dividing the minute volume by the number of heartbeats per minute, you can calculate systolic volume blood.

Systolic blood volume- The volume of blood pumped by each ventricle into the main vessel (aorta or pulmonary artery) during one contraction of the heart is designated as systolic, or stroke, blood volume.

The greatest systolic volume is observed at a heart rate from 130 to 180 beats/min. At heart rates above 180 beats/min, systolic volume begins to decrease significantly.

With a heart rate of 70–75 per minute, the systolic volume is 65–70 ml of blood. In a person with a horizontal body position under resting conditions, the systolic volume ranges from 70 to 100 ml.

metropolitan blood volume is most easily calculated by dividing the minute blood volume by the number of heartbeats per minute. In a healthy person, the systolic blood volume ranges from 50 to 70 ml.

2.Afferent link in the regulation of cardiac activity. The influence of excitation of various reflexogenic zones on the activity of the SS center of the medulla oblongata.

The afferent component of K.'s own reflexes is represented by angioceptors (baro- and chemoreceptors) located in various parts of the vascular bed and in the heart. In some places they are collected in clusters, forming reflexogenic zones. The main ones are the areas of the aortic arch, carotid sinus, and vertebral artery. The afferent link of conjugate reflexes K. is located outside the vascular bed, its central part includes various structures of the cerebral cortex, hypothalamus, medulla oblongata and spinal cord. The vital nuclei of the cardiovascular center are located in the medulla oblongata: neurons of the lateral part of the medulla oblongata, through sympathetic neurons of the spinal cord, have a tonic activating effect on the heart and blood vessels; neurons of the medial part of the medulla oblongata inhibit sympathetic neurons of the spinal cord; the motor nucleus of the vagus nerve inhibits the activity of the heart; neurons of the ventral surface of the medulla oblongata stimulate the activity of the sympathetic nervous system. Through hypothalamus there is a connection between the nervous and humoral parts of the regulation of K.

3. the main hemodynamic factors that determine the value of systemic blood pressure.

Systemic blood pressure, the main hemodynamic factors that determine its value One of the most important hemodynamic parameters is systemic blood pressure, i.e. pressure in the initial parts of the circulatory system - in large arteries. Its magnitude depends on the changes occurring in any department of the system. Along with systemic pressure, there is the concept of local pressure, i.e. pressure in small arteries, arterioles, veins, capillaries. This pressure is less, the longer the path traveled by the blood to this vessel when it leaves the ventricle of the heart. So, in capillaries the blood pressure is greater than in the veins, and is equal to 30-40 mm (beginning) - 16-12 mm Hg. Art. (end). This is explained by the fact that the longer the blood travels, the more energy is spent on overcoming the resistance of the vessel walls, as a result, the pressure in the vena cava is close to zero or even below zero. The main hemodynamic factors influencing the value of systemic blood pressure are determined from the formula: Q = P r r4 / 8 Yu l, Where Q is the volumetric velocity of blood flow in a given organ, r is the radius of the vessels, P is the difference in pressure during “inhalation” and “ exhale" from the organ. The value of systemic blood pressure (BP) depends on the phase of the cardiac cycle. Systolic blood pressure is created by the energy of heart contractions in the systole phase and is 100-140 mm Hg. Art. Its value depends mainly on the systolic volume (output) of the ventricle (CO), total peripheral resistance (R) and heart rate. Diastolic blood pressure is created by the energy accumulated in the walls of large arteries as they stretch during systole. The value of this pressure is 70-90 mm Hg. Art. Its value is determined, to a greater extent, by the values of R and heart rate. The difference between systolic and diastolic pressure is called pulse pressure because... it determines the range of the pulse wave, which is normally equal to 30-50 mm Hg. Art. The energy of systolic pressure is spent: 1) to overcome the resistance of the vascular wall (lateral pressure - 100-110 mm Hg); 2) to create the speed of moving blood (10-20 mm Hg - shock pressure). An indicator of the energy of a continuous flow of moving blood, the resulting value of all its variables, is the artificially allocated average dynamic pressure. It can be calculated using D. Hinema’s formula: Paverage = Pdiastolic 1/3Pulse. The value of this pressure is 80-95 mm Hg. Art. Blood pressure also changes in connection with the phases of respiration: on inspiration, it decreases. Blood pressure is a relatively soft constant: its value can fluctuate throughout the day: during physical work of high intensity, systolic pressure can increase by 1.5-2 times. It also increases with emotional and other types of stress. On the other hand, the blood pressure of a healthy person may decrease relative to its average value. This is observed during slow-wave sleep and, briefly, during orthostatic disturbance associated with the transition of the body from a horizontal to a vertical position.

4.Features of blood flow in the brain and its regulation.

The role of the brain in the regulation of blood circulation can be compared to the role of a powerful monarch, dictator: the amount of systemic blood pressure at any moment of life is calculated for an adequate supply of blood, oxygen to the brain and myocardium. At rest, the brain uses 20% of the oxygen consumed by the entire body and 70% of glucose; cerebral blood flow is 15% of the brain, although the brain mass is only 2% of body mass.

Ticket

1. The concept of extrasystole. The possibility of its occurrence in different phases of the cardiac cycle. Compensatory pause, reasons for its development.

Extrasystole is a heart rhythm disturbance caused by premature contraction of the entire heart or its individual parts due to increased activity of foci of ectopic automatism. It is one of the most common heart rhythm disturbances in both men and women. According to some researchers, extrasystole periodically occurs in almost all people.

Rarely occurring extrasystoles do not affect the state of hemodynamics or the general condition of the patient (sometimes patients experience unpleasant sensations of interruptions). Frequent extrasystoles, group extrasystoles, extrasystoles emanating from various ectopic foci can cause hemodynamic disorders. They are often harbingers of paroxysmal tachycardia, atrial fibrillation, and ventricular fibrillation. Such extrasystoles can undoubtedly be classified as emergency conditions. Conditions are especially dangerous when the ectopic focus of excitation temporarily becomes the pacemaker of the heart, that is, an attack of alternating extrasystoles occurs, or an attack of paroxysmal tachycardia.

Current research suggests that this type of cardiac arrhythmia is often found in individuals considered to be practically healthy. Thus, N. Zapf and V. Hutano (1967) during a single examination of 67,375 people found extrasystole in 49%. K. Averill and Z. Lamb (1960), examining 100 people repeatedly during the day using teleelectrocardiography, detected extrasystole in 30%. Therefore, the idea that interruptions are a sign of heart muscle disease has now been rejected.

G. F. Lang (1957) indicates that extrasystole in approximately 50% of cases is the result of extracardiac influences.

In the experiment, extrasystole is caused by irritation of various parts of the brain - the cerebral cortex, thalamus, hypothalamus, cerebellum, medulla oblongata.

There is an emotional extrasystole that occurs during emotional experiences and conflicts, anxiety, fear, anger. Extrasystolic arrhythmia may be one of the manifestations of general neurosis and altered corticovisceral regulation. The role of the sympathetic and parasympathetic parts of the nervous system in the genesis of cardiac arrhythmias is evidenced by reflex extrasystole that occurs during exacerbation of gastric and duodenal ulcers, chronic cholecystitis, chronic pancreatitis, diaphragmatic hernias, and operations on the abdominal organs. The cause of reflex extrasystole can be pathological processes in the lungs and mediastinum, pleural and pleuropericardial adhesions, and cervical spondyloarthrosis. Conditioned reflex extrasystole is also possible.

Thus, the state of the central and autonomic nervous system plays a large role in the occurrence of extrasystoles.

Most often, the occurrence of extrasystole is facilitated by organic changes in the myocardium. It should be borne in mind that often even minor organic changes in the myocardium in combination with functional factors and, above all, with the discoordinated influences of extracardiac nerves can lead to the appearance of ectopic foci of excitation. In various forms of coronary heart disease, the cause of extrasystole may be changes in the myocardium or a combination of organic changes in the myocardium with functional ones. Thus, according to E.I. Chazov (1971), M.Ya. Ruda, A.P. Zysko (1977), L.T. Malaya (1979), heart rhythm disturbances are observed in 80-95% of patients with myocardial infarction, and the most common rhythm disturbance is extrasystole (ventricular extrasystole is observed in 85-90% of hospitalized patients).