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Rhythmic contraction of the heart muscle, 7 letters, crossword puzzle
A word of 7 letters, the first letter is “C”, the second letter is “I”, the third letter is “C”, the fourth letter is “T”, the fifth letter is “O”, the sixth letter is “L”, the seventh letter is “A”, the word begins with the letter “C”, the last is “A”. If you do not know a word from a crossword puzzle or a crossword puzzle, then our site will help you find the most difficult and unfamiliar words.
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Systole
7-letter word, definitions in scanwords:
rhythmic contraction of the heart (see contraction of 10 letters)
contraction of the atria and ventricles of the heart
contraction of the heart muscle
4 definitions for the word "systole" will help you create your own crossword. Pictures to words in the process of adding.
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Rhythmic contraction of the heart muscle
Answer for the clue "Rhythmic contraction of the heart muscle", 7 letters:
Alternative questions in crossword puzzles for the word systole
Contraction of the atria and ventricles of the heart, in which blood is pumped into the arteries
Rhythmic contraction of the heart
Word definitions for systole in dictionaries
Wikipedia The meaning of the word in the Wikipedia dictionary
Systola is a phonetic phenomenon in ancient verse; shortening the long syllable metri causa (at the request of the meter). Eg. in Greek instead of, instead of; in lat. donec instead of dōnec. The phenomenon of systole usually occurs when a long syllable occurs.
Encyclopedic Dictionary, 1998 Meaning of the word in the dictionary Encyclopedic Dictionary, 1998
SYSTOL (from the Greek systole - contraction) contraction of the atria and ventricles of the heart, in which blood is pumped into the arteries. Systole, together with diastole (relaxation) of the atria and ventricles, constitute the cycle of cardiac activity.
New explanatory and derivational dictionary of the Russian language, T. F. Efremova. The meaning of the word in the dictionary New explanatory and derivational dictionary of the Russian language, T. F. Efremova.
and. Contraction as one of the phases of the heart.
Great Soviet Encyclopedia The meaning of the word in the dictionary Great Soviet Encyclopedia
(from the Greek. systole ≈ contraction, contraction), contraction of the heart muscle, or myocardium; consists of separately, but sequentially flowing S. atria and S. ventricles. Sequential S. and diastole make up the cycle of cardiac activity. In humans, at frequency.
Explanatory dictionary of the Russian language. D.N. Ushakov Meaning of the word in the dictionary Explanatory dictionary of the Russian language. D.N. Ushakov
systoles, pl. no, w. (Greek systole - contraction) (physiol.). Rhythmic contraction of a muscular organ (advantages of the heart).
Dictionary of medical terms Meaning of the word in the dictionary Dictionary of medical terms
phase of the cardiac cycle, consisting of successively flowing contractions of the myocardium of the atria and ventricles.
Examples of the use of the word systole in the literature.
I still remember a whole series of references, filling with a single melody the recollected essence of their reaching, taking them with a fight, reaching out to them, begging from officials, elderly doctors, elderly women of medium height, extremely soulful, possessing some kind of strange resolution and possibility in the essence of the lens of my conversation with my parents about service in the army, which had a foreskin, through which I saw something, prevailed the very ability to consider something, to distinguish to recognize, to contemplate, to have a more or less advantageous, but always natural in its struggle for the will to power, a cacophony of sounds, the mere time of which merged, composed into a jubilant, festive, initially manifesting remnant of meaning, a spring scale of references, seals, paragraphs, rubrics, returning handwriting, the indistinguishability of my name in this schematic hardness and transparency, and another musical seven-part structure of the foundations of the documentation whose letters are produced dressed up in her toga with neon
I also allowed a priori knowledge, as well as a priori synthetic judgments: after all, throughout my life, writing and observing, I myself acted either synthetically or analytically: systole and the diastole of the human spirit were like a second wind to me.
I SEE the seasons slowly change systole and diastole of winter and summer, autumn and spring, fully delineated rhythms of heat and cold, drought and rain, sunlight, fog and darkness.
Three hundred years of diastole - and suddenly came a quick and unexpected systole- as if clenched fist!
And it is precisely the one who lovingly delved into the phenomena of Schelling and Hegel, who, thanks to this, was able to see, to see with love, what could not arise through the philosophy of the West, he had to strive for anthroposophy, for the anthroposophically oriented spiritual science, for the sake of the West, so that we get something that draws from the spirit in the same way as the people of the East drew from the spirit through systole and diastole, and their interaction.
systole
The meaning of the word systole
Dictionary of foreign words
systole [gr. systole contraction, contraction] - a rhythmically repeated contraction of the heart muscle, following its relaxation (diastole).
New explanatory and derivational dictionary of the Russian language. Author T. F. Efremova.
systole Contraction as one of the phases of the heart.
systole s'istole, -s
Explanatory dictionary of the Russian language, ed. D. N. Ushakova
SYSTOL systole, pl. no, w. (Greek systole - contraction) (physiol.). Rhythmic contraction of a muscular organ (advantages of the heart).
Modern explanatory dictionary
SYSTOL (from the Greek systole - contraction), contraction of the atria and ventricles of the heart, in which blood is pumped into the arteries. Systole, together with diastole (relaxation) of the atria and ventricles, constitute the cycle of cardiac activity.
7 letters in the word "systole": a and l o s t.
7-letter words in systole:
Properties of the heart muscle and its diseases
The cardiac muscle (myocardium) in the structure of the human heart is located in the middle layer between the endocardium and the epicardium. It is she who ensures uninterrupted work on the "distillation" of oxygenated blood to all organs and systems of the body.
Any weakness affects the blood flow, requires compensatory restructuring, well-coordinated functioning of the blood supply system. Insufficient ability to adapt causes a critical decrease in the performance of the heart muscle and its disease.
Myocardial endurance is provided by its anatomical structure and empowered.
Structural features
It is customary to judge the development of the muscle layer by the size of the wall of the heart, because the epicardium and endocardium are normally very thin membranes. A child is born with the same thickness of the right and left ventricles (about 5 mm). By adolescence, the left ventricle increases by 10 mm, and the right one by only 1 mm.
In an adult healthy person in the relaxation phase, the thickness of the left ventricle ranges from 11 to 15 mm, the right - 5-6 mm.
Features of muscle tissue are:
- striated striation formed by myofibrils of cardiomyocyte cells;
- the presence of two types of fibers: thin (actin) and thick (myosin), connected by transverse bridges;
- joining myofibrils into bundles, different lengths and orientation, which makes it possible to distinguish three layers (superficial, internal and middle).
The cardiac muscle is different in structure from the skeletal and smooth muscle muscles that provide movement and protection of internal organs.
Morphological features of the structure provide a complex mechanism for contraction of the heart.
How does the heart contract?
Contractility is one of the properties of the myocardium, which consists in creating rhythmic movements of the atria and ventricles, which allow pumping blood into the vessels. The chambers of the heart constantly go through 2 phases:
- Systole - caused by the combination of actin and myosin under the influence of ATP energy and the release of potassium ions from cells, while thin fibers slide over thick ones and the bundles decrease in length. The possibility of undulating motions has been proved.
- Diastole - there is a relaxation and separation of actin and myosin, the restoration of the expended energy due to the synthesis of enzymes, hormones, vitamins obtained through the "bridges".
It has been established that the force of contractions is provided by calcium entering inside the myocytes.
The entire cycle of heart contraction, including systole, diastole and a general pause after them, with a normal rhythm fits into 0.8 seconds. It begins with atrial systole, the ventricles are filled with blood. Then the atria "rest", passing into the diastole phase, and the ventricles contract (systole).
The calculation of the time of "work" and "rest" of the heart muscle showed that per day the state of contraction accounts for 9 hours 24 minutes, and for relaxation - 14 hours 36 minutes.
Sequence of abbreviations, provision physiological features and the needs of the body during stress, unrest depends on the connection of the myocardium with the nervous and endocrine systems, the ability to receive and “decipher” signals, and actively adapt to human living conditions.
The spread of excitation from the sinus node can be traced by the intervals and teeth of the ECG
Cardiac mechanisms providing contraction
The properties of the heart muscle have the following goals:
- support the contraction of myofibrils;
- ensure the correct rhythm for optimal filling of the heart cavities;
- maintain the ability to push blood in any extreme conditions for the body.
To do this, the myocardium has the following abilities.
Excitability - the ability of myocytes to respond to any incoming pathogens. Cells protect themselves from suprathreshold stimuli by a state of refractoriness (loss of the ability to excite). In a normal contraction cycle, absolute refractoriness and relative refractoriness are distinguished.
- During the period of absolute refractoriness, for 200 to 300 ms, the myocardium does not respond even to superstrong stimuli.
- When relative, it is able to respond only to sufficiently strong signals.
With this property, the heart muscle does not allow "distracting" the mechanism of contraction in the systole phase.
Conductivity - the property to receive and transmit impulses to different parts of the heart. It is provided by a special type of myocytes that have processes that are very similar to brain neurons.
Automatism - the ability to create its own action potential inside the myocardium and cause contractions even in a form isolated from the body. This property allows for resuscitation in emergency cases, to maintain the blood supply to the brain. The significance of the located network of cells, their accumulation in the nodes during transplantation of a donor heart is great.
The value of biochemical processes in the myocardium
The viability of cardiomyocytes is ensured by the supply of nutrients, oxygen and the synthesis of energy in the form of adenosine triphosphoric acid.
All biochemical reactions go as far as possible during systole. Processes are called aerobic, because they are possible only with a sufficient amount of oxygen. In a minute, the left ventricle consumes 2 ml of oxygen for every 100 g of mass.
For energy production, delivered with blood are used:
- glucose,
- lactic acid,
- ketone bodies,
- fatty acid,
- pyruvic and amino acids,
- enzymes,
- b vitamins,
- hormones.
In the case of an increase in heart rate (physical activity, excitement), the need for oxygen increases by 40–50 times, and the consumption of biochemical components also increases significantly.
What compensatory mechanisms does the cardiac muscle have?
A person does not develop pathology as long as the compensation mechanisms work well. It is regulated by the neuroendocrine system.
The sympathetic nerve delivers signals to the myocardium about the need for enhanced contractions. This is achieved by a more intense metabolism, increased ATP synthesis.
A similar effect occurs with an increased synthesis of catecholamines (adrenaline, norepinephrine). In such cases, the increased work of the myocardium requires an increased supply of oxygen.
The vagus nerve helps to reduce the frequency of contractions during sleep, during the rest period, to preserve oxygen reserves.
It is important to consider the reflex mechanisms of adaptation.
Tachycardia is caused by congestive stretching of the orifices of the vena cava.
Reflex slowing of the rhythm is possible with aortic stenosis. At the same time, increased pressure in the cavity of the left ventricle irritates the endings of the vagus nerve, contributes to bradycardia and hypotension.
The duration of diastole is increased. Favorable conditions are created for the functioning of the heart. Therefore, aortic stenosis is considered a well-compensated defect. It allows patients to live to a ripe old age.
How to deal with hypertrophy?
Usually prolonged increased load causes hypertrophy. The wall thickness of the left ventricle increases by more than 15 mm. In the mechanism of education important point is the lag of the germination of capillaries deep into the muscle. IN healthy heart number of capillaries per mm2 of cardiac muscle tissue is about 4000, and with hypertrophy, the indicator drops to 2400.
Therefore, the condition up to a certain point is considered compensatory, but with a significant thickening of the wall leads to pathology. It usually develops in that part of the heart, which must work hard to push blood through a narrowed hole or overcome an obstruction of blood vessels.
A hypertrophied muscle is able to maintain blood flow for a long time in case of heart defects.
The muscle of the right ventricle is less developed, it works against a pressure of 15–25 mm Hg. Art. Therefore, compensation for mitral stenosis, cor pulmonale does not last long. But right ventricular hypertrophy is of great importance in acute myocardial infarction, cardiac aneurysm in the area of the left ventricle, relieves congestion. The significant possibilities of the right departments in training during physical exercises have been proved.
Thickening of the left ventricle compensates for defects in the aortic valves, mitral insufficiency
Can the heart adapt to work in conditions of hypoxia?
An important property of adapting to work without sufficient oxygen supply is the anaerobic (oxygen-free) process of energy synthesis. A very rare occurrence in human organs. Activated only in emergencies. Allows the heart muscle to continue contracting.
The negative consequences are the accumulation of decay products and overwork of muscle fibrils. One heart cycle is not enough for energy resynthesis.
However, another mechanism is involved: tissue hypoxia reflexively causes the adrenal glands to produce more aldosterone. This hormone:
- increases the amount of circulating blood;
- stimulates an increase in the content of erythrocytes and hemoglobin;
- enhances venous flow to the right atrium.
This means that it allows the body and myocardium to adapt to a lack of oxygen.
How myocardial pathology occurs, mechanisms of clinical manifestations
Myocardial diseases develop under the influence of different reasons, but appear only when the adaptive mechanisms are disrupted.
Prolonged loss of muscle energy, the impossibility of independent synthesis in the absence of components (especially oxygen, vitamins, glucose, amino acids) lead to thinning of the actomyosin layer, break the bonds between myofibrils, replacing them with fibrous tissue.
This disease is called dystrophy. It accompanies:
- anemia,
- beriberi,
- endocrine disorders,
- intoxications.
Occurs as a result:
Patients experience the following symptoms:
IN young age the most common cause may be thyrotoxicosis, diabetes mellitus. At the same time, there are no obvious symptoms of an enlarged thyroid gland.
Inflammation of the heart muscle is called myocarditis. It accompanies both infectious diseases of children and adults, and those not associated with infection (allergic, idiopathic).
It develops in a focal and diffuse form. The growth of inflammatory elements affects myofibrils, interrupts pathways, changes the activity of nodes and individual cells.
As a result, the patient develops heart failure (more often right ventricular). Clinical manifestations consist of:
- pain in the region of the heart;
- rhythm interruptions;
- shortness of breath;
- expansion and pulsation of the cervical veins.
On the ECG fix atrioventricular blockade of varying degrees.
The most well-known disease caused by impaired blood flow to the heart muscle is myocardial ischemia. It flows like this:
- angina attacks,
- acute heart attack
- chronic coronary insufficiency,
- sudden death.
All forms of ischemia are accompanied by paroxysmal pain. They are figuratively called "the cry of a starving myocardium." The course and outcome of the disease depends on:
- speed of assistance;
- restoration of blood circulation due to collaterals;
- the ability of muscle cells to adapt to hypoxia;
- strong scar formation.
Scandalous drug put on the doping list for giving extra energy to the heart muscle
How to help the heart muscle?
The most prepared for critical impacts are people involved in sports. A clear distinction should be made between cardio training offered by fitness centers and therapeutic gymnastics. Any cardio program is designed for healthy people. Strengthened training allows you to cause moderate hypertrophy of the left and right ventricles. With properly set work, the person himself controls the sufficiency of the load by the pulse.
Physiotherapy exercises are shown to people suffering from any diseases. If we talk about the heart, then it aims to:
- improve tissue regeneration after a heart attack;
- strengthen the ligaments of the spine and eliminate the possibility of pinching of the paravertebral vessels;
- “boost” the immune system;
- restore neuro-endocrine regulation;
- ensure the operation of auxiliary vessels.
Exercise therapy is prescribed by doctors, it is better to master the complex under the supervision of specialists in a sanatorium or medical institution
Treatment with drugs is prescribed in accordance with their mechanism of action.
For therapy, there is currently a sufficient arsenal of means:
- removing arrhythmias;
- improving metabolism in cardiomyocytes;
- enhancing nutrition by expanding the coronary vessels;
- increasing resistance to hypoxic conditions;
- suppressing excess foci of excitability.
You can’t joke with the heart, it’s not recommended to experiment on yourself. Medicines can be prescribed and selected only by a doctor. In order to prevent pathological symptoms for as long as possible, proper prevention is needed. Everyone can help their heart by limiting their intake of alcohol, fatty foods, quitting smoking. Regular physical exercise capable of solving many problems.
Hello, I am 41 years old, I did push-ups from the floor once in the morning and in the evening, now I have pain in the heart area after even the slightest physical exertion or when lifting weights, please tell me what is wrong with my heart and how to treat it?
emergency medicine
The continuous movement of blood through a closed system of vessels of the small and large circles of blood circulation is carried out due to the contractile function of the heart. The systemic circulation supplies the organs of the body with oxygen-rich blood and also collects venous blood and brings it to the heart. In the small (pulmonary) circle of blood circulation, the blood is enriched with oxygen.
Venous blood of a large circle through the right ventricle and pulmonary arteries goes to the lungs, and oxygenated blood enters the left atrium through the pulmonary veins (Fig. 65). Due to the rhythmic contractions of the ventricles, blood is pushed from the left ventricle into the aorta, and from the right ventricle into the pulmonary arteries.
The contraction of the heart muscle occurs in a strict sequence, with a regular rhythm (Fig. 66). In the cardiac cycle, atrial systole is isolated, continuing at a contraction rate of 75 times per 1 min 0.04 - 0.07 s, ventricular systole (0.3 s), ventricular diastole (0.5 s). Atrial systole begins 0.1 s before the end of ventricular diastole. Therefore, atrial diastole lasts 0.7 s.
Joint diastole of the atria and ventricles (pause) lasts 0.4 s. Of the total duration of the cardiac cycle, which in the considered case is 0.9 s, the ventricles are in a state of contraction for 1/3 of the time, and the atria are three times less. Both in systole and in diastole of the ventricles, several phases are distinguished.
In the structure of ventricular contraction, phases of asynchronous and isometric contraction, fast and slow ejection. In the phase of asynchronous contraction of the ventricles, some of the mymental fibers contract, and some relax. The pressure in the ventricles does not change. The duration of this phase at the already considered pulse rate is about 0.05 s.
Asynchronous contraction is replaced by isometric, in which there is a tension of the ventricles with a change in their shape. Intraventricular pressure remains constant. The duration of an isometric contraction is about 0.03 s. Throughout the tension phase, the aortic and atrioventricular valves of the heart remain closed.
The beginning of the ejection phase is accompanied by a steep increase in pressure in the ventricles (rapid ejection). In the phase of slow expulsion, the pressure decreases, but remains higher than in the aorta. The end of the ejection phase - the protodiastolic interval - is characterized by equalization of pressure in the efferent vessels and in the ventricles. These three cycles last 0.3-0.4 s.
The phase of isometric relaxation of the ventricles following the protodiastole is accompanied by a pressure drop to zero. A drop in pressure in the ventricles leads to the opening of the atrioventricular valves of the heart. Blood from the atria first quickly (within 0.06 - 0.08 s), and then slowly (within 0.15 - 0.18 s) fills the ventricles. These are the phases of fast and slow filling. Then there is a repetition of the described pattern of contraction and relaxation of the heart.
Rice. 65. Scheme of the structure of the heart and the direction of blood flow in the cardiac cavities: 1 - aortic arch; 2 - superior vena cava; 3 - right lung; 4 - semilunar valve; 5 - right atrium; 6 - coronary vein; 7 - inferior vena cava; 8 - tricuspid valve; 9 - the rest of the arterial duct; 10 - pulmonary artery; 11 - left lung; 12 - pulmonary vein; 13 - left atrium; 14 - double-leaf valve; 15 - semilunar valve; 16 - tendon thread; 17 - left ventricle; 18 - heart muscle; 19 - aorta; 20 - right ventricle
Rice. 66. Schematic representation of the ratio of mechanical and electrical systoles at rest. Upper curve - electrocardiogram recording, lower curve - phonocardiogram recording
Automatic contraction function. The regular nature of the phase sequence heart contraction due to the autonomous self-regulating system of the heart, called conduction. The conduction system of the heart consists of atypical muscle tissue (glycogen-rich Purkinje muscle fibers). The accumulation of cells of the conducting system (pacemakers) are located in the region of the sinoatrial node, the atrioventricular septum, in the thickness of the muscular walls of the left and right ventricles (the bundles of His fibers).
The primary pacemaker is the sinoatrial node located at the mouth of the vena cava. The cells of this node have the highest rate of spontaneous (spontaneous) depolarization. From the sinoatrial node, excitation spreads along the wall of the right atrium to the atrioventricular node, the secondary pacemaker.
From the atrioventricular node, a thick muscular bundle of His is sent to the septum of the ventricles. The terminal branches of the conduction system of the heart are represented by Purkinje muscle fibers, anastomosing with the contractile fibers of the heart muscle. The conduction system of the heart regulates the rhythmic contractions of the isolated heart.
Under specially created conditions, it is possible to maintain a rhythmic contraction of even individual heart cells for a long time. Spontaneous rhythmic contraction of isolated heart cells is a strong argument in favor of the myogenic nature of cardiac automatism.
Muscle cells of the myocardium - myocytes are interconnected with the help of intercellular intercalated disks - nexuses. Dense packing facilitates excitation in the myocardium, the heart muscle itself contracts as a whole. The cardiac muscle and conduction system of the heart is a functional syncytium. This point of view finds confirmation in electrophysiological experiments.
A feature of the electrical activity of pacemakers is a gradual decrease in membrane potential after the end of systole (diastolic polarization). Having reached a critical level, depolarization is replaced by a sharp shift in the electrical charge of the cell - an action potential indicating its excitation.
The wave of excitation spreads to neighboring cells of the node - the pacemaker. This automatic change in electrical potential is characteristic of all cells of the sinoatrial node of the conducting system.
The contraction of the heart muscle is accompanied by the appearance of tones that are well heard in various areas of the projection of the heart on chest. The first tone - systolic - low-frequency, deaf, long. It coincides with the slamming of the atrioventricular valves. The second tone - diastolic - high, short. It coincides with the closing of the semilunar valves after the end of systole.
Excitability and refractoriness of the heart muscle. Excitability separate parts is not the same. The most excitable is the sinoatrial pacemaker - the Keith-Flak node. The atrioventricular node and fibers of atypical muscle tissue, which are part of the bundles of His, are less excitable. The excitability of the contractile muscles of the heart is much lower than the excitability of its conduction system.
During contraction, the heart muscle does not respond to irritation, its excitability decreases sharply. This is the phase of absolute refractoriness of the heart. In the initial period of relaxation, the excitability of the heart muscle is restored, but does not reach its original value - this is relative refractoriness. At this moment, the heart can respond with an extraordinary contraction - an extrasystole to additional irritation. Relative refractoriness is replaced by a phase of increased excitability - exaltation.
The duration of the absolute refractory phase determines the heart rate. At rest, the heart rate in an adult is in the range of 50 - 75 beats per 1 minute. With muscular and intense mental work, with emotional arousal, the refractoriness of the heart decreases, the pulse rate increases, reaching in some cases 200 or more beats per 1 minute.
Subthreshold stimuli that are weak in strength do not cause heart contractions. When the critical (threshold) strength of the stimulus is reached, the heart responds with a maximum contractile act. The power of cardiac contraction does not depend on the strength of the stimulus: after reaching the threshold value, a further increase in the strength of the stimulus does not affect the power of cardiac output. This phenomenon is known as the all-or-nothing law.
The obvious exception to this law is Frank-Starling's "law of the heart". Stretched by increased blood flow, the heart muscle contracts with greater force (heterometric mechanism for increasing the force of contraction). This is observed when there is an increase in blood flow to the heart. In the stretched fibers of the heart muscle, the area of interaction between actin and myosin filaments increases. Consequently, the contraction force also increases. An increase in cardiac output power in this case has an important adaptive value, for example, at large physical activity the force of cardiac contraction also increases with an increase in pressure in large arteries (homeometric effect).
Rice. 67. Schematic representation of the relationship between areas of excitation of the heart muscle and individual teeth of the electrocardiogram: I - atrial excitation; II - excitation of the atrioventricular node; III - the beginning of excitation of the ventricles; 1 - sinoatrial node; 2 - atrioventricular node (according to E.B. Babsky et al., 1972). Latin letters indicate ECG teeth
Fomin A.F. Human Physiology, 1995
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Contractility function represents the ability of the heart muscle to respond by contraction to the resulting excitation. The force of contraction of the heart fiber is directly proportional to the degree of elongation during diastole and depends on the height blood pressure in the aorta, the amount of remaining blood in the cavities of the heart and the degree of myocardial damage.
Contractile function of the heart is the main one in its activity as a pump, carried out on the basis of the coordination of individual muscle cells. Connecting with each other through intercalary discs in the longitudinal direction and forming lateral holes, the cells form muscle fibers. Intercalated discs are characterized by low electrical resistance, which facilitates the spread of excitation from cell to cell, and thus their contraction.
IN heart two main processes are constantly taking place: the conduction of an electrochemical impulse and the conversion of chemical energy into mechanical energy. Conduction of an electrochemical impulse from cell to cell is carried out with the help of specialized sections of the cell surface - locking fascia. The transformation of chemical energy into mechanical energy occurs in sarcomeres (functional units of the contractile myocardium).
Every muscle contractile myocardial fiber consists of 200-500 contractile protein structures - myofibrils. They contain myosin and actin. Myosin has a specific ability to bind various ions, mainly calcium and magnesium. According to Draper and Hodge (1950), it also contains potassium. VA Engelhardt (1941) showed that myosin has enzymatic properties - the ability to catalyze the breakdown of adenosine triphosphate (ATP) into adenosine diphosphate (ADP) and phosphate. ATP and creatinine phosphate (CP) are produced in mitochondria.
From the moment of cell depolarization before its contraction, a number of biochemical and biophysical changes occur in it. ATP in the presence of myosin and actin is gradually split into ADP and phosphate with the release of energy, and not in the form of heat, since this would release a large number of heat, which would denature the protein. It is assumed that energy during the breakdown of ATP is directly transferred to the contractile structures of the myocardium with the formation of ADP and phosphorylated protein and, without intermediate formation of heat, is converted into electrical energy. Thus, in the heart during systole, ATP breaks down, resulting in a contraction of the heart muscle. In a relaxed muscle, there is a special relaxation factor that occurs in the presence of magnesium ions and ATP. At the moment of contraction, calcium temporarily suppresses the formation of the relaxation factor and neutralizes its effect.
Myocardium consists of two types of cells interconnected by means of the so-called intercalated signs. Most of the muscle cells of the heart perform a contractile function and are called contractile cells - cardiomyocytes.
hallmark myocardium- the presence of intercalary plates that delimit muscle fibers, having a transverse ladder arrangement with respect to muscle fibers. The fibers of the heart muscle are much thinner than the fibers skeletal muscle. They contain more sarcoplasm and less sarcolemma. Important distinguishing features of the heart muscle are a significant number of mitochondria and the absence of longitudinal propagation of excitation through the heart: the impulse jumps from one cell to another in the region of the intercalary plates.
Upkeep calcium increases the contractility of the heart muscle, and its absence makes it impossible to contract the myocardium. The action of calcium on the contraction mechanism is carried out throughout the entire period of membrane depolarization. A decrease in the concentration of extracellular sodium enhances the contractility of the heart muscle, as it increases the rate of calcium penetration into the cell. An increase in sodium concentration blocks the entry of calcium and eliminates contraction. Potassium is indirectly involved in the process muscle activity- leaving the cell during its excitation, it leaves free intracellular anionic sites in the endoplasm, which are occupied by calcium, which ultimately causes contraction.
