Physiological properties and characteristics of the heart muscle. Contraction of the heart muscle. Features of muscle tissue are

The ability of the heart to contract throughout life without stopping is due to a number of specific physical and physiological properties of the heart muscle.

Physical properties. Extensibility - the ability to increase length without breaking the structure under the influence of tensile force. This force is the blood that fills the cavities of the heart during diastole. The strength of their contraction in systole depends on the degree of stretching of the muscle fibers of the heart in diastole.

Elasticity - the ability to restore the original position after the cessation of the deforming force. The elasticity of the heart muscle is complete, i.e. it completely restores the original indicators.

Ability to develop strength during muscle contraction.

Physiological properties. Heart contractions occur as a result of periodically occurring excitation processes in the heart muscle, which has a number of physiological properties: automaticity, excitability, conductivity, contractility.

The ability of the heart to contract rhythmically under the influence of impulses arising within itself is called automatism.

In the heart, a distinction is made between contractile muscles, represented by striated muscle, and atypical, or special tissue, in which excitation occurs and is carried out. Atypical muscle tissue contains a small amount of myofibrils, a lot of sarcoplasm and is not capable of contraction. It is represented by clusters in certain areas of the myocardium, which form the conduction system of the heart, consisting of the sinoatrial node, located on the posterior wall of the right atrium at the confluence of the vena cava; atrioventricular, or atrioventricular node, located in the right atrium near the septum between the atria and ventricles; atrioventricular bundle (bundle of His), extending from the atrioventricular node in one trunk. The bundle of His, passing through the septum between the atria and ventricles, branches into two legs going to the right and left ventricles. The bundle of His ends in the thickness of the muscles with Purkinje fibers.

Sinoatrial node is a pacemaker of the first order. It produces impulses that determine the heart rate. It generates pulses with an average frequency of 70-80 pulses per minute.

Atrioventricular node- second order pacemaker.

Bundle of His - third order pacemaker.

Purkinje fibers- fourth order pacemakers. The firing frequency that occurs in Purkinje fiber cells is very low.

Normally, the atrioventricular node and the His bundle are only transmitters of excitations from the leading node to the heart muscle.

However, they also have automatism, only to a lesser extent, and this automatism manifests itself only in pathology.

In the area of the sinoatrial node, a significant number of nerve cells, nerve fibers and their endings were found, which form a nerve network here. Nerve fibers from the vagus and sympathetic nerves approach the nodes of atypical tissue.

Excitability of the heart muscle is the ability of myocardial cells, when exposed to a stimulus, to enter a state of excitation, in which their properties change and an action potential occurs, and then contraction. Cardiac muscle is less excitable than skeletal muscle. For excitation to occur in it, a stronger stimulus is needed than for the skeletal one. In this case, the magnitude of the reaction of the heart muscle does not depend on the strength of the applied stimulation (electrical, mechanical, chemical, etc.). The heart muscle contracts as much as possible to both threshold and stronger stimulation.

The level of excitability of the heart muscle changes during different periods of myocardial contraction. Thus, additional irritation of the heart muscle during its contraction phase (systole) does not cause a new contraction even under the influence of a superthreshold stimulus. During this period, the heart muscle is in the phase absolute refractoriness. At the end of systole and beginning of diastole, excitability is restored to its original level - this is the phase relative refractoriness. This phase is followed by the phase exaltation, after which the excitability of the heart muscle finally returns to its original level. Thus, a feature of the excitability of the heart muscle is a long refractory period.

Cardiac conductivity is the ability of the heart muscle to conduct excitation arising in any part of the heart muscle to its other parts. Having arisen in the sinoatrial node, excitation spreads through the conduction system to the contractile myocardium. The spread of this excitation is due to the low electrical resistance of the nexuses. In addition, special fibers promote conductivity.

Excitation waves are conducted along the fibers of the cardiac muscle and atypical heart tissue at unequal speeds. Excitation propagates through the fibers of the atrium muscles at a speed of 0.8-1 m/s, through the fibers of the ventricular muscles - 0.8-0.9 m/s, and through atypical heart tissue - 2-4 m/s. When excitation passes through the atrioventricular node, excitation is delayed by 0.02-0.04 s - this is an atrioventricular delay, ensuring coordination of contraction of the atria and ventricles.

Cardiac contractility is the ability of muscle fibers to shorten or change their tension. She reacts to stimuli of increasing strength according to the “all or nothing” law. The heart muscle contracts as a single contraction, since the long refractory phase prevents the occurrence of tetanic contractions. In a single contraction of the heart muscle there are: latent period, shortening phase (systole), relaxation phase (diastole). Due to the ability of the heart muscle to contract only as a single contraction, the heart performs the function of a pump.

The muscles of the atria contract first, then the layer of muscles of the ventricles, thereby ensuring the movement of blood from the cavities of the ventricles into the aorta and pulmonary trunk.

The heart consists of two halves (left and right), each of which in turn consists of an atrium and a ventricle. The left half of the heart pumps out arterial blood, and the right half pumps out venous blood. In this regard, the cardiac muscle of the left half is much larger and thicker than the right. The muscles of the atria and ventricles are separated from each other by fibrous rings that have special valves: bicuspid - on the left heart half, and tricuspid - on the right. These valves prevent blood from returning to the atrium during heart contractions. At the exit from the aorta and pulmonary artery there are valves that visually resemble a crescent. They do not allow blood to return to the ventricles during the general diastole of the heart.

Cardiac muscle is a striated muscle tissue. That is why it has the same properties as skeletal muscles. The fibers they consist of are mainly sarcolemma, myofibrils and sarcoplasm.

The heart circulates blood through the blood vessels. Rhythmic contraction of the muscles of the atria, as well as the ventricles, alternates with their relaxation. The periodic change of systole and diastole constitutes the main cycle of the heart. The heart muscle works quite rhythmically, and this is ensured by a special excitation system located in different parts of the heart.

Physiological characteristics of the heart muscle

Myocardial excitability is the ability to respond to thermal, electrical, chemical or mechanical stimuli. Contraction and excitation of the heart muscle occurs at the moment when the stimulus reaches its maximum strength. Excitations of low impact are not effective, and excessive ones do not change the force of myocardial contraction.

The excited heart muscle for a short period of time loses the ability to respond to additional stimuli and impulses. This reaction is called refractoriness. Stimuli that forcefully impact the muscle during its refractory period provoke an extraordinary contraction of the heart, called an extrasystole.

The rate of excitation differs in different parts of the heart. A characteristic feature of the process of excitation in the cardiac muscle is its action potential, which arises in one area of muscle tissue and gradually spreads to its neighboring areas.

Answers and explanations

The heart muscle is one of the excitable tissues of the body. Excitability is the ability of tissues to produce excitation. Excitation is the basis of functions. One of the main features of the heart muscle is the presence of special contacts between its cells. These contacts are formed by sections of the membranes of adjacent neighboring cells and, thanks to them a special property that allows electric current to spread from cell to cell.

The heart consists of two main groups of cardiac cells: cells of the working myocardium, whose main role is rhythmic contractions; and cells of the conducting system;

1) sinus node located in the right atrium

2) antioventricular node, located at the border of the atria and ventricles;

3) directly conducting system;

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The heart is a muscle consisting of 4 chambers (in humans), 2 ventricles and 2 atria. This organ constantly contracts and pushes out blood.

In one contraction the heart pumps 80 ml, in a minute it pumps about 5 liters, but when a person works the number of contractions increases.

Features of the heart include:

High endurance and good blood supply.

3.2. Structure of the heart. Properties of the heart muscle

The heart is located in the chest cavity as part of the mediastinal organs, shifted to the left. The position and weight of the heart depend on the body type, shape of the chest, gender and age of the person. On average, women have less heart weight (250 g) than men (300 g). Athletes and people involved in physical labor have larger heart sizes than people not involved in heavy physical activity.

The heart is a hollow muscular organ divided internally into four cavities: the right and left atria, the right and left ventricles. The heart wall consists of three layers: the inner endothelial layer with valves - the endocardium, the middle muscular layer - the myocardium and the outer connective tissue layer covered with single-layer epithelium - the epicardium. The outside of the heart is covered by a pericardial sac - the pericardium. The cavity between the epicardium and pericardium contains a small amount of serous fluid, which reduces friction during heart contractions. In the left half of the heart, between the atrium and the ventricle, there is a bicuspid (mitral) valve, in the right half there is a tricuspid valve. At the mouth of the aorta there are semilunar valves that prevent blood from returning to the ventricle. The middle layer of the heart wall (myocardium) is formed by muscle cells - cardiomyocytes. In the atria the myocardium is thinner, in the ventricles it is thicker (especially in the left ventricle). The myocardium in structure belongs to the striated muscles, but has a number of features. Cardiomyocytes are tightly connected to each other, forming a functionally unified tissue - syncytium, due to which the rapid conduction of excitation and simultaneous contraction of the entire heart are carried out. Conducting excitation in the myocardium to all working cardiomyocytes performs conducting system heart, which is formed by atypical muscle cells.

Thanks to these cells, the myocardium has specific properties:

1) automatic– ability of atypical muscle cells

the conductive system generates impulses without any external influences;

2) conductivity– the ability of the conductive system to transmit excitation;

3) excitability – the ability of heart muscle cells to be excited under the influence of impulses that come through the conduction system of the heart;

4) contractility – the ability to contract under the influence of these impulses.

Impulses arise in the so-called pacemaker (pacemaker), which is located in the right atrium at the mouth of the vena cava - sinoatrial node or first order node. It generates impulses with a frequency of 60 – 80 contractions per minute (60 – 80 imp/min). Second order knot located in the atrioventricular septum - atrioventricular node. The speed of excitation from the first-order node to the second-order node is 1 m/s, but in the second-order node the conduction speed drops to 0.02 - 0.05 m/s, resulting in an interval between atrial contractions and ventricular contractions. Starts from a second-order node His bundle, dividing into right and left legs, which further break down into Purkinje fibers, in direct contact with myocardial fibers. In the His bundle, the conduction speed reaches 5 m/s, and then in the Purkinje fibers the conduction speed again decreases to 1 m/s. The bundle branches can generate contractions at a frequency of 30–40 impulses/min. Individual Purkinje fibers can generate impulses at a frequency of 20 contractions per minute. The decrease in the ability to automaticity, starting from the base of the heart to the apex, is the so-called decreasing gradient of automation.

Features of excitability and contractility of the heart muscle.

An important feature of cardiac muscle excitability is the presence of prolonged refractory period, i.e. a period of reduced sensitivity to excitation, longer than in other striated muscles. The frequency of generation of excitation by the cells of the conduction system and, accordingly, myocardial contractions is determined by the duration of the refractory phase, which occurs after each systole and is about 0.3 s in the heart. A long refractory period has important biological significance for the heart, since it protects the myocardium from too frequent re-excitation and contraction. The heart muscle contracts according to the “all or nothing” law, since it has close contacts between individual muscle cells - the so-called nexuses, or areas of close contact (common part of the membranes), as a result of which excitation flows unhindered from one cell to another. The myocardium is a functionally unified system, therefore excitation quickly covers the entire muscle and simultaneous contraction of all muscle cells of the ventricles occurs. The work of the heart directly depends on oxygen consumption. Oxygen is delivered to the tissues of the heart through the coronary arteries, which arise from the aorta. During ventricular systole, the valves block the mouths of the coronary arteries, preventing blood from flowing to the heart. When the ventricles relax, the sinuses fill with blood, and the valves block its path back to the left ventricle, at the same time the mouths of the coronary arteries open and blood flows to the heart. Since the heart requires a continuous supply of sufficiently large quantities of oxygen to the cells, blockage of the coronary arteries leads to severe disruption of the heart and the rapid development of foci of necrosis (myocardial infarction). Having given up oxygen, venous blood in the wall of the heart collects in the anterior cardiac veins and venous sinus, which open into the cavity of the right and left atria.

The amount of blood flow in the vessels of the ventricles during their systole decreases, so the flow of blood, the delivery of oxygen and nutrients to the myocardium is mainly ensured during diastole. The heart rate increases mainly due to the contraction of diastole, so as the heart rate increases, the supply of oxygen to the myocardium decreases.

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Anatomy and physiology of the heart: structure, functions, hemodynamics, cardiac cycle, morphology

The structure of the heart of any organism has many characteristic nuances. In the process of phylogenesis, that is, the evolution of living organisms to more complex ones, the heart of birds, animals and humans acquires four chambers instead of two chambers in fish and three chambers in amphibians. This complex structure is best suited for separating the flow of arterial and venous blood. In addition, the anatomy of the human heart involves many small details, each of which performs its own strictly defined functions.

Heart as an organ

So, the heart is nothing more than a hollow organ consisting of specific muscle tissue, which carries out the motor function. The heart is located in the chest behind the sternum, more to the left, and its longitudinal axis is directed anteriorly, to the left and down. In front, the heart borders on the lungs, almost completely covering them, leaving only a small part directly adjacent to the chest from the inside. The boundaries of this part are otherwise called absolute cardiac dullness, and they can be determined by tapping the chest wall (percussion).

In people with a normal constitution, the heart has a semi-horizontal position in the chest cavity, in people with an asthenic constitution (thin and tall) it is almost vertical, and in hypersthenics (dense, stocky, with large muscle mass) it is almost horizontal.

The posterior wall of the heart is adjacent to the esophagus and to the large main vessels (thoracic aorta, inferior vena cava). The lower part of the heart is located on the diaphragm.

external structure of the heart

Age characteristics

The human heart begins to form in the third week of the intrauterine period and continues throughout the entire period of gestation, passing through stages from a single-chamber cavity to a four-chamber heart.

development of the heart in utero

The formation of four chambers (two atria and two ventricles) occurs already in the first two months of pregnancy. The smallest structures are fully formed by birth. It is in the first two months that the heart of the embryo is most vulnerable to the negative influence of certain factors on the expectant mother.

The fetal heart participates in the blood flow throughout its body, but differs in its circulatory circles - the fetus does not yet have its own lungs to breathe, but “breathes” through the placental blood. There are some openings in the fetal heart that allow pulmonary blood flow to be “switched off” from the circulation before birth. During childbirth, accompanied by the first cry of the newborn, and, consequently, at the moment of increased intrathoracic pressure and pressure in the baby's heart, these openings close. But this does not always happen, and the child may still have them, for example, an open foramen ovale (not to be confused with a defect such as atrial septal defect). An open window is not a heart defect, and subsequently, as the child grows, it closes.

hemodynamics in the heart before and after birth

The heart of a newborn baby has a round shape, and its dimensions are 3-4 cm in length and 3-3.5 cm in width. In the first year of a child's life, the heart increases significantly in size, more in length than in width. The weight of a newborn baby's heart is about a gram.

As the baby grows and develops, the heart also grows, sometimes significantly ahead of the development of the body itself according to age. By the age of 15, the mass of the heart increases almost tenfold, and its volume increases more than fivefold. The heart grows most rapidly until the age of five, and then during puberty.

In an adult, the size of the heart is about a cm in length and 8-10 cm in width. Many people rightly believe that the size of each person’s heart corresponds to the size of his clenched fist. The weight of the heart in women is about 200 grams, and in men it is about a gram.

After age 25, changes begin in the connective tissue of the heart, which forms the heart valves. Their elasticity is no longer the same as in childhood and adolescence, and the edges may become uneven. As a person grows and then ages, changes occur in all structures of the heart, as well as in the vessels that feed it (the coronary arteries). These changes can lead to the development of numerous cardiac diseases.

Anatomical and functional features of the heart

Anatomically, the heart is an organ divided into four chambers by septa and valves. The “upper” two are called atria (atrium), and the “lower” two are called ventricles (ventriculum). Between the right and left atria is the interatrial septum, and between the ventricles is the interventricular septum. Normally, these septa do not have holes in them. If there are holes, this leads to mixing of arterial and venous blood, and, accordingly, to hypoxia of many organs and tissues. Such holes are called septal defects and are classified as heart defects.

basic structure of the chambers of the heart

The boundaries between the upper and lower chambers are the atrioventricular openings - the left one, covered by the mitral valve leaflets, and the right one, covered by the tricuspid valve leaflets. The integrity of the septa and the proper operation of the valve leaflets prevent the mixing of blood flows in the heart and promote clear unidirectional blood flow.

The atria and ventricles are different - the atria are smaller than the ventricles and have thinner walls. Thus, the wall of the atria is about only three millimeters, the wall of the right ventricle is about 0.5 cm, and the wall of the left is about 1.5 cm.

The atria have small projections called ears. They have a slight suction function for better pumping of blood into the atrium cavity. The mouth of the vena cava flows into the right atrium near its appendage, and four (less often five) pulmonary veins flow into the left atrium. The pulmonary artery (more often called the pulmonary trunk) on the right and the aortic bulb on the left depart from the ventricles.

structure of the heart and its vessels

From the inside, the upper and lower chambers of the heart are also different and have their own characteristics. The surface of the atria is smoother than the ventricles. Thin connective tissue valves originate from the valve ring between the atrium and the ventricle - bicuspid (mitral) on the left and tricuspid (tricuspid) on the right. The other edge of the valves faces the inside of the ventricles. But so that they do not hang freely, they are supported, as it were, by thin tendon threads called chords. They are like springs, stretch when the valve flaps close and compress when the valve flaps open. The chordae originate from the papillary muscles from the wall of the ventricles - three in the right and two in the left ventricle. That is why the ventricular cavity has an uneven and lumpy inner surface.

The functions of the atria and ventricles also differ. Due to the fact that the atria need to push blood into the ventricles, and not into larger and longer vessels, they have to overcome less resistance from muscle tissue, therefore the atria are smaller in size and their walls are thinner than those of the ventricles. The ventricles push blood into the aorta (left) and the pulmonary artery (right). Conventionally, the heart is divided into right and left halves. The right half serves for the flow of exclusively venous blood, and the left half for arterial blood. Schematically, the “right heart” is indicated in blue, and the “left heart” in red. Normally, these flows never mix.

hemodynamics in the heart

One cardiac cycle lasts about 1 second and is carried out as follows. At the moment the atria are filled with blood, their walls relax - atrial diastole occurs. The valves of the vena cava and pulmonary veins are open. The tricuspid and mitral valves are closed. Then the atrial walls tense and push blood into the ventricles, the tricuspid and mitral valves are open. At this moment, systole (contraction) of the atria and diastole (relaxation) of the ventricles occur. After the ventricles receive blood, the tricuspid and mitral valves close, and the aortic and pulmonary valves open. Next, the ventricles contract (ventricular systole), and the atria fill with blood again. The general diastole of the heart begins.

The main function of the heart is reduced to pumping, that is, to pushing a certain blood volume into the aorta with such pressure and speed that the blood is delivered to the most distant organs and to the smallest cells of the body. Moreover, arterial blood with a high content of oxygen and nutrients is pushed into the aorta, entering the left half of the heart from the vessels of the lungs (flows to the heart through the pulmonary veins).

Venous blood, low in oxygen and other substances, is collected from all cells and organs from the venous cava system, and flows into the right half of the heart from the superior and inferior vena cava. Next, venous blood is pushed from the right ventricle into the pulmonary artery, and then into the pulmonary vessels in order to carry out gas exchange in the alveoli of the lungs and to enrich it with oxygen. In the lungs, arterial blood collects in the pulmonary venules and veins, and again flows into the left side of the heart (the left atrium). And so the heart regularly pumps blood throughout the body at a frequency of beats per minute. These processes are designated by the concept of “circulation of blood.” There are two of them - small and large:

The minor circle includes the flow of venous blood from the right atrium through the tricuspid valve into the right ventricle - then into the pulmonary artery - then into the arteries of the lungs - oxygenation of the blood in the pulmonary alveoli - flow of arterial blood into the smallest veins of the lungs - into the pulmonary veins - into the left atrium .
The great circle includes the flow of arterial blood from the left atrium through the mitral valve into the left ventricle - through the aorta into the arterial bed of all organs - after gas exchange in the tissues and organs, the blood becomes venous (with a high content of carbon dioxide instead of oxygen) - then into the venous bed of the organs - into the vena cava system - into the right atrium.

Video: cardiac anatomy and cardiac cycle briefly

Morphological features of the heart

In order for the heart muscle fibers to contract synchronously, electrical signals must be supplied to them, which excite the fibers. This is another ability of the heart - conductivity.

Conduction and contractility are possible due to the fact that the heart autonomously generates electricity. These functions (automaticity and excitability) are provided by special fibers that are an integral part of the conduction system. The latter is represented by electrically active cells of the sinus node, atrioventricular node, the bundle of His (with two legs - right and left), as well as Purkinje fibers. In the case when a patient’s myocardial damage affects these fibers, heart rhythm disturbances, otherwise called arrhythmias, develop.

Normally, the electrical impulse originates in the cells of the sinus node, which is located in the area of the right atrium appendage. In a short period of time (about half a millisecond), the impulse spreads throughout the atrial myocardium and then enters the cells of the atrioventricular junction. Typically, signals are transmitted to the AV node through three main tracts - the Wenkenbach, Thorel and Bachmann bundles. In the cells of the AV node, the impulse transmission time is extended to milliseconds, and then the impulses travel through the right and left branches (as well as the anterior and posterior branches of the left branch) of the His bundle to the Purkinje fibers, and ultimately to the working myocardium. The frequency of impulse transmission along all pathways is equal to the heart rate and amounts to impulses per minute.

So, the myocardium, or cardiac muscle, is the middle layer in the wall of the heart. The inner and outer membranes are connective tissue and are called endocardium and epicardium. The last layer is part of the pericardial sac, or cardiac “shirt”. Between the inner layer of the pericardium and the epicardium, a cavity is formed, filled with a very small amount of fluid, to ensure better sliding of the pericardial layers during heart contractions. Normally, the fluid volume is up to 50 ml; exceeding this volume may indicate pericarditis.

structure of the heart wall and membrane

Blood supply and innervation of the heart

Despite the fact that the heart is a pump to supply the entire body with oxygen and nutrients, it itself also needs arterial blood. In this regard, the entire wall of the heart has a well-developed arterial network, which is represented by the branching of the coronary (coronary) arteries. The orifices of the right and left coronary arteries depart from the root of the aorta and are divided into branches that penetrate the thickness of the heart wall. If these critical arteries become clogged with blood clots and atherosclerotic plaques, the patient will develop a heart attack and the organ will no longer be able to perform its full functions.

location of the coronary arteries supplying blood to the heart muscle (myocardium)

The frequency and force with which the heart beats is influenced by nerve fibers extending from the most important nerve conductors - the vagus nerve and the sympathetic trunk. The first fibers have the ability to slow down the rhythm frequency, the latter - to increase the frequency and strength of the heartbeat, that is, they act like adrenaline.

In conclusion, it should be noted that the anatomy of the heart may have any deviations in individual patients, therefore, only a doctor can determine the norm or pathology in a person after conducting an examination that can most informatively visualize the cardiovascular system.

Human cardiac muscle, its features and functions

The heart is a hollow organ. It is approximately the size of a human fist. The heart muscle forms the walls of the organ. It has a partition dividing it into left and right halves. Each of them contains a network of ventricle and atrium. The direction of blood flow in the organ is controlled by valves. Next, let's take a closer look at the properties of the heart muscle.

General information

The heart muscle – the myocardium – makes up the bulk of the organ’s mass. It consists of three types of fabric. In particular, they distinguish: atypical myocardium of the conduction system, fibers of the atrium and ventricles. Measured and coordinated contraction of the heart muscle is ensured by the conduction system.

Structure

The heart muscle has a mesh structure. It is formed from fibers woven into a network. Connections between fibers are established due to the presence of lateral jumpers. Thus, the network is presented in the form of a narrow-loop syncytium. Connective tissue is present between the fibers of the heart muscle. It has a loose structure. In addition, the fibers are entwined with a dense network of capillaries.

Properties of the heart muscle

The structure contains intercalary disks, presented in the form of membranes, separating fiber cells from each other. Important features of the heart muscle should be noted here. Individual cardiomyocytes, present in large numbers in the structure, are connected to each other in parallel and in series. Cell membranes fuse to form highly permeable gap junctions. Ions diffuse through them unhindered. Thus, one of the features of the myocardium is the free movement of ions through the intracellular fluid along the entire myocardial fiber. This ensures unimpeded distribution of action potentials from one cell to another through the intercalary discs. It follows from this that the heart muscle is a functional union of a huge number of cells that have a close relationship with each other. It is so strong that when only one cell is excited, it provokes the potential to spread to all other elements.

Myocardial syncytia

There are two of them in the heart: atrial and ventricular. All parts of the heart are separated from each other by fibrous septa with openings equipped with valves. Excitation from the atrium to the ventricle cannot pass directly through the tissue of the walls. Transmission is carried out through a special atrioventricular bundle. Its diameter is several millimeters. The bundle consists of fibers of the conducting structure of the organ. The presence of two syncytia in the heart causes the atria to contract before the ventricles. This, in turn, is of utmost importance for ensuring effective pumping activity of the organ.

Myocardial diseases

The functioning of the heart muscle can be impaired due to various pathologies. Depending on the provoking factor, specific and idiopathic cardiomyopathies are distinguished. Heart disease can also be congenital or acquired. There is another classification, according to which restrictive, dilated, congestive and hypertrophic cardiomyopathies are distinguished. Let's look at them briefly.

Hypertrophic cardiomyopathy

To date, experts have identified gene mutations that provoke this form of pathology. Hypertrophic cardiomyopathy is characterized by thickening of the myocardium and changes in its structure. Against the background of pathology, muscle fibers increase in size, “twist”, taking on strange shapes. The first symptoms of the disease are observed in childhood. The main signs of hypertrophic cardiomyopathy are chest tenderness and shortness of breath. There is also uneven heart rhythm, and ECG reveals changes in the heart muscle.

Congestive form

This is a fairly common type of cardiomyopathy. As a rule, the disease occurs in men. Pathology can be recognized by signs of heart failure and disturbances in heart rhythm. Some patients experience hemoptysis. The pathology is also accompanied by pain in the heart area.

Dilated cardiomyopathy

This form of the disease manifests itself in the form of a sharp expansion in all chambers of the heart and is accompanied by a decrease in the contractility of the left ventricle. As a rule, dilated cardiomyopathy occurs in combination with hypertension, coronary heart disease, and aortic stenosis.

Restrictive form

Cardiomyopathy of this type is diagnosed extremely rarely. The cause of the pathology is the inflammatory process in the heart muscle and complications after intervention on the valves. Against the background of the disease, the myocardium and its membranes degenerate into connective tissue, and slow filling of the ventricles is noted. The patient experiences shortness of breath, fatigue, valve defects and heart failure. The restrictive form is considered extremely dangerous for children.

How to strengthen the heart muscle?

There are various ways to do this. Activities include correction of the daily routine and diet, exercises. As a preventative measure, after consulting with your doctor, you can start taking a number of medications. In addition, there are traditional methods of strengthening the myocardium.

Physical activity

It should be moderate. Physical activity should become an integral element of the life of any person. In this case, the load must be adequate. Do not overload the heart and exhaust the body. The best options are race walking, swimming, and cycling. Exercises are recommended to be done in the fresh air.

Walking

It is excellent not only for strengthening the heart, but also for healing the entire body. When walking, almost all human muscles are involved. In this case, the heart additionally receives a moderate load. If possible, especially at a young age, it is worth giving up the elevator and walking over heights.

Lifestyle

Strengthening the heart muscle is impossible without adjusting your daily routine. To improve myocardial activity, it is necessary to stop smoking, which destabilizes blood pressure and causes narrowing of the lumen in the blood vessels. Cardiologists also do not recommend getting carried away with baths and saunas, since staying in a steam room significantly increases cardiac stress. It is also necessary to take care of normal sleep. You should go to bed on time and get enough rest.

Diet

Rational nutrition is considered one of the most important measures in strengthening the myocardium. You should limit the amount of salty and fatty foods. Products must contain:

Magnesium (legumes, watermelons, nuts, buckwheat).
Potassium (cocoa, raisins, grapes, apricots, zucchini).
Vitamins P and C (strawberries, black currants, peppers (sweet), apples, oranges).
Iodine (cabbage, cottage cheese, beets, seafood).

Cholesterol in high concentrations has a negative effect on myocardial activity.

Psycho-emotional state

Strengthening the heart muscle can be complicated by various unresolved problems of a personal or work nature. They can cause pressure changes and rhythm disturbances. Stressful situations should be avoided whenever possible.

Drugs

There are several means that help strengthen the myocardium. These include, in particular, drugs such as:

"Riboxin" Its action is aimed at stabilizing the rhythm, enhancing nutrition of the muscles and coronary vessels.
"Asparkam." This drug is a magnesium-potassium complex. Thanks to taking the drug, electrolyte metabolism is normalized and signs of arrhythmia are eliminated.
Rhodiola rosea. This remedy improves the contractile function of the myocardium. Caution should be exercised when taking this drug as it has the ability to excite the nervous system.

Human heart muscle

Physiological properties of the heart muscle

Blood can perform its many functions only by being in constant motion. Ensuring blood movement is the main function of the heart and blood vessels that form the circulatory system. The cardiovascular system, together with the blood, is also involved in the transport of substances, thermoregulation, the implementation of immune reactions and the humoral regulation of body functions. The driving force for blood flow is created by the work of the heart, which acts as a pump.

The ability of the heart to contract throughout life without stopping is due to a number of specific physical and physiological properties of the heart muscle. Cardiac muscle uniquely combines the qualities of skeletal and smooth muscles. Just like skeletal muscles, the myocardium is capable of working intensely and contracting quickly. Just like smooth muscles, it is practically tireless and does not depend on a person’s volitional effort.

Physical properties

Extensibility - the ability to increase length without breaking the structure under the influence of tensile force. This force is the blood that fills the cavities of the heart during diastole. The strength of their contraction in systole depends on the degree of stretching of the muscle fibers of the heart in diastole.

Elasticity is the ability to restore its original position after the cessation of the deforming force. The elasticity of the heart muscle is complete, i.e. it completely restores the original indicators.

The ability to develop force during muscle contraction.

Physiological properties

Heart contractions occur as a result of periodically occurring excitation processes in the heart muscle, which has a number of physiological properties: automaticity, excitability, conductivity, contractility.

The ability of the heart to contract rhythmically under the influence of impulses arising within itself is called automatism.

The sinoatrial node is the first order pacemaker. It produces impulses that determine the heart rate. It generates pulses with an average pulse frequency of 1 minute.

The atrioventricular node is a second-order pacemaker.

The His bundle is a third-order pacemaker.

Purkinje fibers are fourth-order pacemakers. The firing frequency that occurs in Purkinje fiber cells is very low.

Normally, the atrioventricular node and the His bundle are only transmitters of excitations from the leading node to the heart muscle.

However, they also have automatism, only to a lesser extent, and this automatism manifests itself only in pathology.

The level of excitability of the heart muscle changes during different periods of myocardial contraction. Thus, additional irritation of the heart muscle during its contraction phase (systole) does not cause a new contraction even under the influence of a superthreshold stimulus. During this period, the heart muscle is in a phase of absolute refractoriness. At the end of systole and beginning of diastole, excitability is restored to its original level - this is the relative refractory/pi phase. This phase is followed by a phase of exaltation, after which the excitability of the heart muscle finally returns to its original level. Thus, a feature of the excitability of the heart muscle is a long refractory period.

Cardiac contractility is the ability of muscle fibers to shorten or change their tension. She reacts to stimuli of increasing strength according to the “all or nothing” law. The heart muscle contracts as a single contraction, since the long refractory phase prevents the occurrence of tetanic contractions. In a single contraction of the heart muscle there are: latent period, shortening phase ([[|systole]]), relaxation phase (diastole). Due to the ability of the heart muscle to contract only as a single contraction, the heart performs the function of a pump.

The muscles of the atria contract first, then the layer of muscles of the ventricles, thereby ensuring the movement of blood from the cavities of the ventricles into the aorta and pulmonary trunk.

STRUCTURE OF THE HEART WALL

The wall of the heart consists of three layers: inner - endocardium, average - myocardium and external - epicardium.

Endocardium lines the inside surface of the chambers of the heart, it is formed by a special type of epithelial tissue - endothelium. The endothelium has a very smooth, shiny surface, which reduces friction as blood moves through the heart.

Myocardium makes up the bulk of the heart wall.

He is educated transversely-striated cardiac muscle tissue, the fibers of which, in turn, are arranged in several layers. The atrial myocardium is much thinner than the ventricular myocardium. The myocardium of the left ventricle is three times thicker than the myocardium of the right ventricle. The degree of development of the myocardium depends on the amount of work performed by the chambers of the heart. The myocardium of the atria and ventricles is separated by a layer of connective tissue (annulus fibrosus), which makes it possible to alternately contract the atria and ventricles.

Epicard- This is a special serous membrane of the heart, formed by connective and epithelial tissue.

PERICARDIAL BAG (PERICARDIUM)

This is a kind of closed bag in which the heart is enclosed. The bag consists of two sheets. The inner leaf fuses over the entire surface with the epicardium. The outer leaf seems to cover the inner leaf on top. There is a slit-like cavity between the inner and outer leaves - pericardial cavity), filled with liquid. The bag itself and the fluid contained in it play a protective role and reduce friction of the heart during its operation. The bag helps fix the heart in a certain position.

HEART VALVES

The functioning of the heart valves ensures the one-way movement of blood in the heart.

The actual heart valves include flap valves located at the border of the atria and ventricles. On the right side of the heart is flap valve, in the left - bicuspid (mitral). The flapper valve consists of three elements: 1) doors , dome-shaped and formed by dense connective tissue, 2) papillary muscle, 3) tendon threads , stretched between the valve and the papillary muscle. When the ventricles contract, the leaflet valves close the gap between the atrium and the ventricle. The mechanism of operation of these valves is as follows: when the pressure in the ventricles increases, blood rushes into the atria, lifting the valve flaps, and they close, breaking the lumen between the atrium and the ventricle; the valves do not turn towards the atria, because they are held in place by tendon threads that are stretched by contraction of the papillary muscle.

At the border of the ventricles and the vessels extending from them (aorta and pulmonary trunk), there are semilunar valves, consisting of semilunar valves . There are three such valves in the named vessels. Each semilunar valve has the shape of a thin-walled pocket, the entrance to which is open towards the vessel. When blood is expelled from the ventricles, the semilunar valves are pressed against the walls of the vessel. During relaxation of the ventricles, blood rushes in the opposite direction, fills the “pockets”, they move away from the walls of the vessel and close, blocking the lumen of the vessel, preventing blood from entering the ventricles. The semilunar valve, located at the border of the right ventricle and the pulmonary trunk, is called pulmonary valve, at the border of the left ventricle and aorta - aortic valve.

Heart functions

The function of the heart is that the myocardium of the heart pumps blood from the venous to the arterial vascular bed during contraction. The source of energy necessary for the movement of blood through the vessels is the work of the heart. The energy of contraction of the myocardium of the heart is converted into pressure imparted to the portion of blood pushed out of the heart during contraction of the ventricles. Blood pressure- this is the force that is spent to overcome the force of friction of the blood against the walls of the blood vessels. The pressure difference in different parts of the vascular bed is the main reason for blood movement. The movement of blood in the cardiovascular system in one direction is ensured by the work of the heart and vascular valves.

Properties of the heart muscle

The main properties of the heart muscle include automaticity, excitability, conductivity And contractility.

1. Automatic- this is the ability to rhythmically contract without any external influences under the influence of impulses arising in the heart itself. A striking manifestation of this property of the heart is the ability of a heart removed from the body to contract within hours and even days when the necessary conditions are created. The nature of automation is still not fully understood. But it is clearly clear that the occurrence of impulses is associated with the activity atypical muscle fibers, embedded in some areas of the myocardium. Electrical impulses of a certain frequency are spontaneously generated inside atypical muscle cells, which then spread throughout the myocardium. The first such area is located in the area of the mouth of the vena cava and is called sinus, or sinoatrial node. In the atypical fibers of this node, impulses spontaneously occur with a frequency of 60-80 times per minute. It is the main center of heart automation. The second section is located in the thickness of the septum between the atria and ventricles and is called atrioventricular, or atrioventricular node. The third section is the atypical fibers that make up His bundle, lying in the interventricular septum. Thin fibers of atypical tissue originate from the bundle of His - Purkinje fibers, branching in the ventricular myocardium. All areas of atypical tissue are capable of generating impulses, but their frequency is highest in the sinus node, which is why it is called first-order pacemaker (first-order pacemaker), and all other centers of automation obey this rhythm.

The totality of all levels of atypical muscle tissue is conduction system of the heart. Thanks to the conduction system, the excitation wave that arises in the sinus node consistently spreads throughout the entire myocardium.

2. Excitability of the heart muscle is that under the influence of various stimuli (chemical, mechanical, electrical, etc.), the heart is able to enter a state of excitation. The excitation process is based on the appearance of a negative electrical potential on the outer surface of the membranes of cells exposed to the stimulus. As in any excitable tissue, the membrane of muscle cells (myocytes) is polarized. At rest, it is charged positively on the outside and negatively on the inside. The potential difference is determined by the different concentrations of N a + and K + ions on both sides of the membrane. The action of the stimulus increases the permeability of the membrane for K + and Na + ions, a restructuring of the membrane potential occurs ( potassium - sodium pump), resulting in an action potential that spreads to other cells. In this way, excitation spreads throughout the heart.

Impulses originating in the sinus node spread throughout the atrium muscles. Having reached the atrioventricular node, the excitation wave propagates along the His bundle and then along the Purkinje fibers. Thanks to the conduction system of the heart, a sequential contraction of parts of the heart is observed: first the atria contract, then the ventricles (starting from the apex of the heart, the wave of contraction spreads to their base). A feature of the atrioventricular node is that it conducts the excitation wave in only one direction: from the atria to the ventricles.

3. Contractility- This is the ability of the myocardium to contract. It is based on the ability of the myocardial cells themselves to respond to stimulation with contraction. This property of the cardiac muscle determines the ability of the heart to perform mechanical work. The work of the heart muscle obeys the law "all or nothing".The essence of this law is as follows: if an irritating effect of varying strength is applied to the heart muscle, the muscle responds each time with a maximum contraction (“ All "). If the strength of the stimulus does not reach the threshold value, then the heart muscle does not respond with contraction (" Nothing ").

General information

The heart muscle - the myocardium - makes up the bulk of the organ's mass. It consists of three types of fabric. In particular, they distinguish: atypical myocardium of the conduction system, fibers of the atrium and ventricles. Measured and coordinated contraction of the heart muscle is ensured by the conduction system.

Structure

Properties of the heart muscle

Myocardial syncytia

Myocardial diseases

Hypertrophic cardiomyopathy

To date, experts have identified gene mutations that provoke this form of pathology. Hypertrophic cardiomyopathy is characterized by thickening of the myocardium and changes in its structure. Against the background of pathology, muscle fibers increase in size, “twist”, acquiring strange shapes. The first symptoms of the disease are observed in childhood. The main signs of hypertrophic cardiomyopathy are chest tenderness and shortness of breath. There is also uneven heart rhythm, and ECG reveals changes in the heart muscle.

Congestive form

This is a fairly common type of cardiomyopathy. As a rule, the disease occurs in men. Pathology can be recognized by signs of heart failure and disturbances in heart rhythm. Some patients experience hemoptysis. The pathology is also accompanied by pain in the heart area.

Dilated cardiomyopathy

Restrictive form

How to strengthen the heart muscle?

Physical activity

Walking

Lifestyle

Diet

Rational nutrition is considered one of the most important measures in strengthening the myocardium. You should limit the amount of salty and fatty foods. Products must contain:

Magnesium (legumes, watermelons, nuts, buckwheat).
Potassium (cocoa, raisins, grapes, apricots, zucchini).
Vitamins P and C (strawberries, black currants, peppers (sweet), apples, oranges).
Iodine (cabbage, cottage cheese, beets, seafood).

Cholesterol in high concentrations has a negative effect on myocardial activity.

Psycho-emotional state

Drugs

There are several means that help strengthen the myocardium. These include, in particular, drugs such as:

"Riboxin". Its action is aimed at stabilizing the rhythm, enhancing nutrition of the muscles and coronary vessels.
"Asparkam." This drug is a magnesium-potassium complex. Thanks to taking the drug, electrolyte metabolism is normalized and signs of arrhythmia are eliminated.
Rhodiola rosea. This remedy improves the contractile function of the myocardium. Caution should be exercised when taking this drug as it has the ability to excite the nervous system.