Changes in the activity of the heart during physical work. Physiological bases of physical activity. Work of the heart during exercise

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

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

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

Question 4 Age features of the development of the motor apparatus in children and adolescents 11

List of used literature.. 13

Question 1 Phases of the cardiac cycle and their changes during exercise

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 (cavity of the heart) presses in all directions, including on the walls of this vessel. The ventricles are the structure that creates this gradient.

The cyclically repeated change in 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 heart departments are in the following state: the semilunar valves are closed, and the atrioventricular valves are open. Blood from the veins enters freely and completely fills the cavities of the atria and ventricles. The blood pressure in them is the same as in the nearby veins, about 0 mm Hg. Art.

The excitation that originated in the sinus node first of all goes 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). At the same time, the contraction of muscle fibers located around the mouths of the veins overlaps them. A closed atrioventricular cavity is formed. With the contraction of the atrial myocardium, the pressure in them rises to 3-8 mm Hg. Art. As a result, part of the blood from the atria through the open atrioventricular openings passes into the ventricles, bringing the blood volume in them to 110-140 ml (end-diastolic ventricular volume - EDV). At the same time, due to the incoming additional portion of blood, the cavity of the ventricles is somewhat stretched, which is especially pronounced in their longitudinal direction. After this, ventricular systole begins, and at the atria - diastole.

After an atrioventricular delay (about 0.1 s), excitation along the fibers of the conducting system spreads to ventricular cardiomyocytes, and ventricular systole begins, lasting about 0.33 s. The systole of the ventricles 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. At the same time, 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 an asynchronous contraction phase (0.05 s), since not all ventricular fibers begin to contract at the same time. The cardiomyocytes located near the fibers of the conducting system are the first to contract. This is followed by the isometric contraction phase (0.03 s), which is characterized by the involvement of the entire ventricular myocardium in the contraction.

The onset of ventricular contraction leads to the fact that, with the semilunar valves still closed, blood rushes to the area of \u200b\u200blowest pressure - back towards the atria. The atrioventricular valves in its path are closed by the blood flow. Tendon threads keep them from dislocation into the atria, and contracting papillary muscles create even more emphasis. As a result, for some time there are closed cavities of the ventricles. And until the contraction of the ventricles raises the blood pressure in them above the level necessary for the opening of the semilunar valves, a significant shortening of the length of the fibers does not occur. Only their inner tension increases.

The second period - the period of expulsion of blood - begins with the opening of the valves of the aorta and pulmonary artery. 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 mm Hg. 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 rises 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) contributes to the rapid ejection of part of the blood into the vessel.

However, the relatively small capacity of the vessels, in which there was blood before, leads to their overflow. Now the pressure is rising already in the vessels. The pressure gradient between the ventricles and vessels gradually decreases, as the rate of blood ejection slows down.

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 cavity of the ventricles, 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 - ESC). The cessation of expulsion leads to the fact that the blood in the vessels slams the semilunar valves with a reverse current. This state is called the proto-diastolic interval (0.04 s). Then there is a drop in tension - 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 passively flowing blood through the veins. But it is possible to single out an "active" component, which manifests itself in connection with the partial coincidence of their diastole with the ventricular systole. With the contraction of the latter, 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 about 20-30%. But this contribution increases significantly with the intensification of the work of the heart, when the total diastole is shortened, and the blood does not have time to fill the ventricles sufficiently.

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 with blood flow is removed from the working muscle to those parts of the body where it is returned. 3-6 minutes after the start of light work, a stationary (sustainable) increase in heart rate occurs, which is due to the irradiation of excitation from the motor cortex to the cardiovascular center of the medulla oblongata and the flow of activating impulses to this center from the chemoreceptors of the working muscles. Activation of the muscular apparatus enhances blood supply in the working muscles, which reaches a maximum within 60-90 seconds after the start of work. With light work, a correspondence is formed between blood flow and the metabolic needs of the muscle. In the course of light dynamic work, the aerobic pathway of ATP resynthesis begins to dominate, using glucose, fatty acids and glycerol as energy substrates. In heavy dynamic work, the heart rate increases to a maximum as fatigue develops. Blood flow in working muscles increases 20-40 times. However, the delivery of O 3 to the muscles lags behind the needs of muscle metabolism, and part of the energy is generated due to anaerobic processes.

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

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 temporal characteristics of the process of movement of contents through the sections of the gastrointestinal tract are judged by the movement of an X-ray contrast agent (for example, barium sulphate). After taking it, it begins to enter the caecum after 3-3.5 hours. Within 24 hours, the colon is filled, which is released from the contrast mass after 48-72 hours.

The initial sections of the colon are characterized by very slow small pendulum contractions. With their help, the chyme is mixed, which accelerates the absorption of water. In the transverse colon and sigmoid colon, large pendulum contractions are observed, caused by the excitation of a large number of longitudinal and circular muscle bundles. The 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 large intestine is promoted by anti-peristaltic contractions, which move the contents in a retrograde direction and thereby promote the absorption of water. Condensed dehydrated chyme accumulates in the distal colon. This segment of the intestine is separated from the overlying, filled with liquid chyme, 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, such reductions are called mass reductions. 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 epitheliocytes, lymphoid cells and mucus. The liquid component has a pH of 8.5-9.0. Juice enzymes are contained mainly in desquamated epitheliocytes, during the decay 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 is much lower than in the juice of the small intestine. But the available enzymes are sufficient to complete the hydrolysis in the proximal colon of the remnants of undigested nutrients.

The regulation of juice secretion of the mucous membrane of the large intestine is carried out mainly due to enteral local nervous mechanisms.

Similar information.

Physical loads cause restructuring of various body functions, the features and degree of which depend on the power, the nature of motor activity, the level of health and fitness. The influence of physical activity on a person can only be judged on the basis of a comprehensive consideration 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 depends, first of all, on the individual characteristics of a person and his level of fitness. At the heart of the development of fitness, in turn, is the process of adaptation of the body to physical stress. Adaptation - a set of physiological reactions that underlies the body's adaptations to changing 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 of which is the achievement of a new level of performance. Adaptation of the body to physical stress consists in the mobilization and use of the functional reserves of the body, the improvement of the existing physiological mechanisms of regulation. No new functional phenomena and mechanisms are observed in the process of adaptation, just the existing mechanisms begin to work more perfectly, more intensively and more economically (decrease in heart rate, deepening of breathing, etc.).

The process of adaptation 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 exercises impose different requirements 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, the shifts that occur in the internal environment of the body are compensated faster, 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 systems that provide oxygen transport, namely, the blood system and the respiratory system, are of great importance.

Blood and circulatory system

The body of an adult 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 the exit from the “depot”). It is redistributed 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 meeting the increased need for oxygen in the body. 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, the mass of blood increases, the amount of hemoglobin increases (by 1–3%), the number of erythrocytes increases (by 0.5–1 million in cubic mm), the number of leukocytes and their activity increase, which increases the body's resistance to colds and infectious diseases. diseases. As a result of muscle activity, the blood coagulation system is activated. This is one of the manifestations of the urgent adaptation of the body to the effects of physical exertion and possible injuries, followed by bleeding. By programming such a situation “in advance”, 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 mass 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 muscular activity contributes to the hypertrophy of the heart muscle and an increase in its cavities. Athletes have 30% more heart volume than 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 contributes to a change in the activity of not only the heart, but also blood vessels. Active motor activity causes the expansion of blood vessels, a decrease in the tone of their walls, and an increase in their elasticity. During physical exertion, the microscopic capillary network is almost completely opened, which at rest is only 30-40% active. All this allows you to significantly accelerate blood flow and, consequently, 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 heartbeats 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 - 45-55 beats / min and below. Decrease in heart rate as a result of systematic exercise is called bradycardia. Bradycardia prevents “wear and tear of the myocardium and is of great health importance. During the day, during which there were no trainings and competitions, the sum of the daily pulse in athletes is 15–20% less than in people of the same sex and age who do not go in for sports.

Muscular activity causes an increase in heart rate. With intense muscular work, the heart rate can reach 180-215 beats / min. It should be noted that the 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 muscular work, the heart rate in less trained individuals is much higher. In addition, during the performance of any motor activity, the heart rate changes depending on gender, age, well-being, training conditions (temperature, air humidity, time of day, etc.).

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

Important indicators of the performance of the heart are systolic and minute volume. Systolic volume of blood (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 - 70-80 ml, in untrained - 50-70 ml. The greatest systolic volume is observed at a heart rate of 130–180 beats/min. With a heart rate over 180 beats / min, it is greatly reduced. Therefore, the best opportunities for training the heart have physical activity in the mode of 130-180 beats / min. Minute blood volume - the amount of blood ejected by the heart in one minute, depends on the heart rate and systolic blood volume. At rest, the minute volume of blood (MBC) averages 5-6 liters, with light muscular work it increases to 10-15 liters, with strenuous physical work in athletes it can reach 42 liters or more. An increase in the IOC during muscle activity provides an increased need for blood supply to organs and tissues.

Respiratory system

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

Table 2.2

Mean indicators of cardiovascular response

and respiratory systems for physical activity

Parameters		With intense physical activity
Heart rate	50–75 bpm	160–210 bpm
systolic blood pressure	100–130 mmHg Art.	200–250 mmHg 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 and 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. MPC is the maximum amount of oxygen that a person is able to consume within one minute per 1 kg of weight. MIC is measured in milliliters per minute per 1 kg of body weight (ml/min/kg). MPC is an indicator of the body's aerobic capacity, i.e., the ability to perform intense muscular work, providing energy costs due to oxygen absorbed directly during work. The value of the IPC can be determined by mathematical calculation using special nomograms; it is possible in laboratory conditions when working on a bicycle ergometer or climbing a step. BMD depends on age, state of the cardiovascular system, body weight. To maintain health, it is necessary to have the ability to consume oxygen by at least 1 kg - for women at least 42 ml / min, for men - at least 50 ml / min. When less oxygen enters the tissue cells than is necessary to fully meet the energy needs, oxygen starvation, or hypoxia, occurs.

oxygen debt- this is the amount of oxygen that is required for the oxidation of metabolic products formed during physical work. With intense physical exertion, as a rule, metabolic acidosis of varying severity is observed. Its cause is the “acidification” of the blood, i.e., the accumulation of metabolic metabolites in the blood (lactic, pyruvic acids, etc.). To eliminate these metabolic products, oxygen is needed - an oxygen demand is created. When the oxygen demand is higher than the 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 arises. Oxygen debt is liquidated after the end of work. The time of 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 release of digestive juices, activates intestinal motility, and increases the efficiency of digestion processes.

However, with 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 process of active digestion of abundant food within 2-3 hours after its intake reduces the efficiency of muscle activity, since the digestive organs in this situation appear to be more in need of increased blood circulation. In addition, a full stomach raises the diaphragm, thereby complicating the activity of the respiratory and circulatory organs. That is why the physiological pattern requires taking food 2.5-3.5 hours before the start of the workout, and 30-60 minutes after it.

excretory system

During muscular activity, the role of the 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, releasing sebum, form a protective, softening layer on the surface of the body; the lacrimal glands provide moisture that wets the mucous membrane of the eyeball. However, the main role in the release of the body from the end products of metabolism 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, by increasing the activity of the excretory function, significantly help the kidneys in removing decay products from the body, which are formed during intense metabolic processes.

Nervous system in motion control

When controlling movements, the central nervous system performs a very complex activity. To perform clear targeted movements, it is necessary to continuously receive signals to the central nervous system about the functional state of the muscles, about the degree of their contraction and relaxation, about the posture of the body, about the position of the joints and the angle of bend in them. All this information is transmitted from the receptors of sensory systems, and especially from the receptors of the motor sensory system, located in muscle tissue, tendons, and articular bags. From these receptors, by the principle of feedback and by the mechanism of the CNS reflex, complete information is received about the performance of a motor action and about its comparison with a given program. With repeated repetition of a motor action, the impulses from the receptors reach the motor centers of the CNS, 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 by 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 the 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 large. In this phase, movements are constrained, uneconomical, inaccurate and poorly coordinated.

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

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

People who lead an active lifestyle have a high chance of not being at risk of developing cardiovascular disease. 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 great 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
ischemic 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 big physical stress on the heart. That is why they are advised to include training before a serious load in the regime. This will serve as such a "warm-up" of the muscles of the heart, balance the pulse. In no case should you abruptly quit training, the heart is used to moderate loads, if they don’t, hypertrophy of the heart muscles can occur.

The influence of professions on the work of the heart

Conflicts, stress, lack of normal rest negatively affects the work of the heart. A list of professions that negatively affect the heart was compiled: athletes take the first place, politicians the second; the third is 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 an inactive lifestyle, physical activity is practically absent.
Work 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 just to lead an active lifestyle: do housework, often walk in the fresh air, do yoga or light physical education.

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FGBOUVPO VOLGOGRAD STATE ACADEMY OF PHYSICAL CULTURE

CDS No. 1 on the topic:

Regulation of the activity of the heart

Performed:

Student 204 groups

Azimli R.Sh.

Volgograd 2015

Bibliography

1. Physiological properties of the heart muscle and their differences from the skeletal

blood flow contraction cardiac athlete

The physiological properties of the heart muscle include excitability, contractility, conductivity and automaticity.

Excitability is the ability of cardiomyocytes and the entire heart muscle to be excited by the action of mechanical, chemical, electrical and other stimuli on it, which is used in cases of sudden cardiac arrest. A feature of the excitability of the heart muscle is that it obeys the law "all or nothing." This means that the heart muscle does not respond to a weak, sub-threshold stimulus, (i.e., it is not excited and does not contract) ("nothing") , and the heart muscle responds to a threshold stimulus sufficient to excite with its maximum contraction (“all”) and with a further increase in the strength of irritation, the response from the heart does not change. This is due to the structural features of the myocardium and the rapid spread of excitation through it through the intercalated disks - nexuses and anastomoses of muscle fibers.Thus, the strength of heart contractions, unlike skeletal muscles, does not depend on the strength of irritation.However, this law, discovered by Bowditch, is largely arbitrary, since certain conditions affect the manifestation of this phenomenon - temperature, degree of fatigue, muscle extensibility and a number of other factors.

Conductivity is the ability of the heart to conduct excitation. The speed of excitation in the working myocardium of different parts of the heart is not the same. In the atrial myocardium, excitation spreads at a speed of 0.8--1 m/s, in the ventricular myocardium-- 0.8-0.9 m/s. In the atrioventricular region, in a section 1 mm long and wide, the conduction of excitation slows down to 0.02–0.05 m/s, which is almost 20–50 times slower than in the atria. As a result of this delay, ventricular excitation begins 0.12–0.18 s later than the start of atrial excitation. There are several hypotheses explaining the mechanism of atrioventricular delay, but this issue requires further study. However, this delay has a great biological meaning - it ensures the coordinated work of the atria and ventricles.

Contractility. The contractility of the heart muscle has its own characteristics. The strength of heart contractions depends on the initial length of muscle fibers (Frank-Starling law). The more blood flows to the heart, the more its fibers will be stretched and the greater will be the force of heart contractions. This is of great adaptive importance, providing a more complete emptying of the cavities of the heart from blood, which maintains a balance in the amount of blood flowing to the heart and flowing from it. A healthy heart, even with a slight stretch, responds with an increased contraction, while a weak heart, even with a significant stretch, only slightly increases the force of its contraction, and the outflow of blood is carried out due to the increase in the rhythm of heart contractions. In addition, if for some reason there has been an excessive stretching of the heart fibers beyond the physiologically permissible limits, then the strength of subsequent contractions no longer increases, but weakens.

Automation is a property that skeletal muscles do not possess. This property implies the ability of the heart to be rhythmically excited without a stimulus from the external environment.

2. Heart rate and cardiac cycle at rest and during muscular work

Heart rate (pulse) - jerky oscillations of the walls of the arteries associated with cardiac cycles. In a broader sense, the pulse is understood as any changes in the vascular system associated with the activity of the heart, therefore, in the clinic, arterial, venous and capillary pulses are distinguished.

Heart rate depends on many factors, including age, gender, body position, and environmental conditions. It is higher in the vertical position compared to the horizontal, decreases with age. Resting heart rate lying down - 60 beats per minute; standing-65. Compared to the lying position in the sitting position, the heart rate increases by 10%, while standing by 20-30%. The average heart rate is about 65 per minute, but there are significant fluctuations. In women, this figure is 7-8 higher.

Heart rate is subject to diurnal fluctuations. During sleep, it is reduced by 2-7, within 3 hours after eating it increases, especially if the food is rich in proteins, which is associated with blood flow to the abdominal organs. Ambient temperature has an effect on heart rate, which increases linearly with effective temperature.

In trained individuals, resting heart rate is lower than in untrained individuals and is about 50-55 beats per minute.

Physical activity leads to an increase in heart rate, which is necessary to ensure an increase in cardiac output, and there are a number of patterns that make it possible to use this indicator as one of the most important in carrying out stress tests.

There is a linear relationship between heart rate and work intensity within 80-90% of the maximum load limit.

With light exercise, the heart rate initially increases significantly, but gradually decreases to a level that persists throughout the period of stable exercise. With more intense loads, there is a tendency to increase heart rate, and at maximum work it increases to the maximum achievable. This value depends on fitness, age, gender and other factors. In trained people, the heart rate reaches 180 beats / min. When working with variable power, we can talk about the frequency range of contractions of 130-180 beats / min, depending on the change in power.

The optimal frequency is 180 beats / min at various loads. It should be noted that the work of the heart at a very high rate of contractions (200 or more) becomes less efficient, since the filling time of the ventricles is significantly reduced and the stroke volume of the heart decreases, which can lead to pathology (V.L. Karpman, 1964; E.B. Sologub, 2000).

Tests with increasing loads until the maximum heart rate is used only in sports medicine, and the load is considered acceptable if the heart rate reaches 170 per minute. This limit is usually used in determining exercise tolerance and the functional state of the cardiovascular and respiratory systems.

3. Systolic and minute volume of blood flow at rest and during muscular work in trained and untrained athletes

The systolic (stroke) volume of blood is the amount of blood that the heart ejects into the appropriate vessels with each contraction of the ventricle.

The greatest systolic volume is observed at a heart rate of 130 to 180 beats/min. At a heart rate above 180 beats/min, systolic volume begins to decline strongly.

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

At rest, the volume of blood ejected from the ventricle is normally from one third to one half of the total amount of blood contained in this chamber of the heart by the end of diastole. The reserve volume of blood remaining in the heart after systole is a kind of depot that provides an increase in cardiac output in situations in which a rapid intensification of hemodynamics is required (for example, during exercise, emotional stress, etc.).

Minute volume of blood (MBV) - the amount of blood pumped by the heart into the aorta and pulmonary trunk in 1 minute.

For the conditions of physical rest and the horizontal position of the body of the subject, the normal values of the IOC correspond to the range of 4-6 l/min (values of 5-5.5 l/min are more often given). The average values of the cardiac index range from 2 to 4 l / (min. m2) - values of the order of 3-3.5 l / (min. m2) are more often given.

Since the volume of blood in a person is only 5-6 liters, the complete circulation of the entire blood volume occurs in about 1 minute. During hard work, the IOC in a healthy person can increase to 25-30 l / min, and in athletes - up to 35-40 l / min.

In the oxygen transport system, the circulatory apparatus is a limiting link, therefore, the ratio of the maximum value of the IOC, which manifests itself during the most intense muscular work, with its value under conditions of basal metabolism, gives an idea of the functional reserve of the entire cardiovascular system. The same ratio also reflects the functional reserve of the heart itself in terms of its hemodynamic function. The hemodynamic functional reserve of the heart in healthy people is 300-400%. This means that the resting IOC can be increased by 3-4 times. In physically trained individuals, the functional reserve is higher - it reaches 500-700%.

Factors affecting systolic volume and minute volume:

1. body weight, which is proportional to the weight of the heart. With a body weight of 50 - 70 kg - the volume of the heart is 70 - 120 ml;

2. the amount of blood entering the heart (venous return of blood) - the greater the venous return, the greater the systolic volume and minute volume;

3. The strength of heart contractions affects the systolic volume, and the frequency affects the minute volume.

4. Electrical phenomena in the heart

Electrocardiography is a technique for recording and studying electric fields generated during the work of the heart. Electrocardiography is a relatively inexpensive but valuable method of electrophysiological instrumental diagnostics in cardiology.

The direct result of electrocardiography is to obtain an electrocardiogram (ECG) - a graphical representation of the potential difference arising from the work of the heart and conducted to the surface of the body. The ECG reflects the averaging of all vectors of action potentials that occur at a certain moment in the work of the heart.

Bibliography

1. A.S. Solodkov, E.B. Sologub ... Human Physiology. General. Sports. Age: Textbook. Ed. 2nd.

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