The physiology of the heart is a concept in whichshould understand any doctor. This knowledge is very important in clinical practice and allows you to understand the work of the heart in a normal manner, so that if necessary, compare the indicators when the pathology of the cardiac muscle works.
First, you need to understand what the functions areheart, the physiology of this organ will then be more understandable. So, the main function of the heart muscle is the injection of blood from the vein into the artery at a rhythmic rate, at which a pressure gradient is created, which entails its uninterrupted movement. That is, the function of the heart is to provide blood circulation with a blood message of kinetic energy. Many people associate myocardium with a pump. Only, in contrast to this mechanism, the heart is characterized by high productivity and speed, smoothness of transient processes and margin of safety. The tissues are constantly renewed in the heart.
To understand the physiology of the blood circulation of the heart, it is necessary to understand what circulatory components exist.
Кровеносная система состоит из четырех элементов:heart muscle, blood vessels, regulation mechanism and organs that are blood depots. This system is a component of the cardiovascular system (the cardiovascular system also includes the lymphatic system).
Thanks to the presence of the latter system, bloodContinuously moves along the vessels. But this is influenced by factors such as: the work of the heart muscle as a "pump", the difference in the level of pressure in the cardiovascular system, the valves of the heart and veins that prevent blood from flowing back, as well as being withdrawn. In addition, the elasticity of the walls of the vessels, the negative pressure of the intrapleural, thanks to which the blood "sucks" and more easily returns to the heart through the veins, as well as the force of gravity of the blood. Owing to the reduction of skeletal muscles, blood is pushed, breathing becomes more frequent and deep, and this leads to the fact that pleural pressure decreases, the activity of proprioceptors increases, increasing excitability in the central nervous system and the frequency of contractions of the heart muscle.
In the human body there are two circlesblood circulation: large and small. Together with the heart they form a system of a closed type. Understanding the physiology of the heart and blood vessels, one should understand how the blood circulates through them.
Еще в 1553 году М.Servetus described a small circle of blood circulation. It originates from the right ventricle and passes into the pulmonary trunk and then into the lungs. It is in the lungs that gas exchange takes place, then the blood passes through the veins of the lung and arrives at the left atrium. Due to this, oxygen is enriched with blood. Further, saturated with oxygen, it flows into the left ventricle, in which a large circle originates.
About the great circle of blood circulation to mankind has becomeknown in 1685, and opened it to W. Harvey. According to the basics of the physiology of the heart and the circulatory system, the blood that is enriched with oxygen moves along the aorta, heading towards small vessels through which it is transferred to organs and tissues. Gas exchange occurs in them.
Also in the human body is the upper and lowerhollow veins flowing into the right atrium. Venous blood moves through them, which contains a little oxygen. It should also be noted that, on a large scale, arterial blood passes through the arteries, and the venous blood passes through the veins. In the small circle, the opposite is true.
Теперь давайте разберемся в физиологии сердца more in detail. Myocardium is a cross-striated muscle tissue, which consists of special individual cells called cardiomyocytes. These cells are connected with each other by nexus and form a muscle fiber of the heart. Myocardium is not an anatomically integral organ, but it works as syncytium. Nexus quickly excite from one cell to another.
According to the physiology of the structure of the heart, in ittwo types of muscles are distinguished according to the peculiarities of functioning, and this is atypical musculature and an active myocardium, which consists of muscle fibers characterized by a fairly developed striped-transverse striation.
The physiology of the heart suggests that this body has several physiological properties. And this:
As for excitability, it isthe ability of striated muscles to respond to nerve impulses. It is not as large as that of similar skeletal type muscles. The cells of the active myocardium are characterized by a large amount of membrane potential, which causes their reaction only to significant irritation.
The physiology of the cardiac system is such that due to the fact that the conducting excitation rate is small, the atria and ventricles begin to contract alternately.
Refractoriness, on the contrary, is inherent in longperiod that is related to the validity period. Due to the fact that the refractory period is long, the heart muscle is reduced by a single type, as well as by the law “either all or nothing”.
Атипичным мышечным волокнам присущи weakly pronounced contractility properties, but at the same time such fibers have a high level of metabolic processes. Here, mitichondria come to the rescue, whose function is similar to that of nerve fibers. Mithichondria conduct nerve impulses and provide generation. The conductive system of the heart is formed precisely due to the atypical myocardium.
Studying the physiology of the heart, shouldto mention that the atypical muscle conduction system consists of the sinoatrial node, located on the right side of the posterior wall, on the border separating the superior and inferior vena cava, the atrioventricular node, which sends impulses to the ventricles (located below the interatrial septum), the His bundle (passes through the atrial gastric septum in the ventricle). Another component of the atypical muscle is Purkinje fiber, whose branches are given to cardiomyocytes.
There are also other structures here:Kent and Meygayl bundles (the first go along the lateral edge of the heart muscle and connect the ventricles and the atrium, and the second is located below the atrioventricular node and transmits signals to the ventricles without affecting the His bundles). It is thanks to these structures, in case the atrioventricular node is turned off, the transfer of impulses is ensured, which entail the receipt of unnecessary information in case of illness and cause an additional contraction of the heart muscle.
The physiology of the functions of the heart is such that the contraction of the heart muscle can be called a well-organized periodic process. Organize this process helps the cardiac conduction system.
Since the heart is rhythmically reduced, the bloodperiodically expelled into the circulatory system. The heart cycle is the period when the heart muscle contracts and relaxes. This cycle consists of ventricular and atrial systole, as well as a pause. When atrial systole pressure increases from 1-2 millimeters of mercury to 6-9 and up to 8-9 millimeters of mercury in the right and left atria, respectively. As a result, blood flows to the ventricles through the atrioventricular openings. When the pressure in the left and right ventricles reaches 65 and 5-12 millimeters of mercury, respectively, expulsion of blood occurs and ventricular diastole occurs, causing a rapid drop in pressure in the ventricles. This increases the pressure in large vessels, which leads to the slamming of the semilunar valves. When the pressure in the ventricles drops to zero, the valves will open and the phase at which the ventricles fill up will begin. This phase ends diastole.
What is the duration of the cardiac cycle phasesmuscles? This question interests many people interested in the physiology of heart regulation. Only one thing can be said: their duration is a variable value. Here, the decisive factor is the frequency of the rhythm of the heart muscle. If the functions of the heart become upset, then with the same rhythm the duration of the phase may vary.
External signs of her work are characteristic of the heart muscle. These include:
Minute and systolic volumes of the myocardium are also indicators of his work.
В то время, когда происходит систола желудочков, the heart makes a turn from left to right, changing the original ellipsoid shape to rounded. In this case, the upper part of the heart muscle rises and presses on the chest in the V-shaped intercostal space on the left side. This is the apical impulse.
Что касается физиологии тонов сердца, то о них should be mentioned separately. Tones are sound phenomena that occur during the work of the heart muscle. In total, the heart produces two tones. The first tone - he is systolic - which is characteristic of atrioventricular valves. The second tone - diastolic - occurs at the time of closing the valves of the pulmonary trunk and the aorta. The first tone is long, deaf and lower than the second. The second tone is high and short.
In total, there are two laws of cardiac activity: the law of the heart fiber and the rhythm of the heart muscle.
Первый (О. Франка - Э.Starling) states that the more stretched the muscle fiber, the stronger its further contraction will be. The level of stretching is affected by the volume of blood that has accumulated in the heart during the diastole period. The greater the volume, the more vigorous the reduction during systole will be.
The second (F. Bainbridge) states that when blood pressure rises in the hollow veins (in the mouths), an increase in the frequency and strength of muscle contractions at the reflex level is observed.
Both of these laws work simultaneously. They are referred to the mechanism of self-regulation, which helps to adapt the work of the heart muscle to different conditions of existence.
Considering the physiology of the heart brieflyto mention that certain hormones, mediators and mineral salts (electrolytes) also affect the work of this body. For example, acetylhopin (mediator) and an excess of potassium ions weaken the heart activity, making the rhythm rare, as a result of which even cardiac arrest may occur. A large number of calcium ions, adrenaline and norepinephrine, on the contrary, contribute to the strengthening of cardiac activity and its increase. Adrenaline, moreover, dilates the coronary vessels, thereby improving the nutrition of the myocardium.
In accordance with the body's need for oxygen and nutrition, the frequency and strength of contractions of the heart muscle can vary. The activity of the heart is regulated by special neurohumoral mechanisms.
But the heart has its own mechanisms.regulation of activity. Some of them are directly related to the properties possessed by myocardial fibers. Here there is a relationship between the force of contraction of the fiber and the rhythm of the heart muscle, as well as the dependence of the contraction energy and the degree of fiber stretching during the diastole period.
The elastic property of myocardial fibers, whichnot manifested in the process of active conjugation, is called passive. The carriers of elastic properties are the supporting-trophic skeleton, as well as actomyosin bridges, which are also located in the non-active muscle. The skeleton has a very positive effect on myocardial elasticity when sclerotic processes occur.
If a person has ischemic contracture or inflammatory diseases of the myocardium, the bridge stiffness increases.
The work of the cardiovascular system iscomplex process. Any failure can lead to negative consequences. Check with your doctor regularly and do not neglect his recommendations. After all, to prevent the disease is much easier than to treat it, spending money on expensive medicines.
