(Lat. CR, Greek Cardia) - Hollow fibrous-muscular organ located in the middle chest Between two lungs and lying on the diaphragm. Towards midline The heart is located asymmetrically - about 2/3 to the left of it and about 1/3 - right.
Heart size The person is about equal to its fist, on average weighs 220-260 grams (up to 500 g.).
How the heart works
The heart pumps blood throughout the body, saturating the cells with oxygen and nutrient substances. The heart can be considered a real intersection of highways, the controller of the "movement" of blood, since it converges veins and arteries, and it continuously acts as a pump - in one reduction, it pushes 60-75 ml of blood into vessels (up to 130 ml). Normal Pulse In a calm state - 60-80 blows per minute, and in women the heart beats by 6-8 blows per minute more often than in men. With severe exercise The pulse can accelerate to 200 or more shots per minute. During the day, the heart is reduced about 100,000 times, pumping from 6,000 to 7,500 liters of blood or 30-37 full baths with a capacity of 200 liters.
The pulse is formed when pushing the blood from the left ventricle in the aorta and in the form of a wave applies to arteries at a speed of 11 m / s, that is, 40 km / h.
| The power developed by the heart while reducing | 70-90 |
| Heart work: | |
| With one cut, J (kgf · m) | 1 (0,102) |
| During the day, KJ (kgf · m) | 86,4 (8810) |
| Medium power developed by heart, W (hp) | 2,2 (0,003) |
| The volume of blood emitted by the heart for one reduction, see 3 | 60-80 |
| The volume of blood emitted by heart, l: | |
| For 1 min | |
| with 70 heartbeats per minute | 4,2-5,6 |
| With ski races | 25-35 |
| when the average intensity | 18 |
| For 1 tsp | 252-336 |
| per day | 6050-8100 |
| per year, million | 2,2-3,0 |
Blood moves into the heart of the eight
: From the veins flows into the right atria, then the right ventricle pushes it into the lungs, where it is saturated with oxygen and returns through the pulmonary veins to the left atrium. Then in the left ventricle and from it through the aorta, and the arterial vessels that branches from it are spread throughout the body.
Giving oxygen, the blood is collected in hollow veins, and through them - in the right atria and the right ventricle. From there through the pulmonary artery, the blood enters the lungs, where again enriched with oxygen.
Not fully clear how the brain manages to maintain the synchronicity of the heart activity and 40 thousand kilometers (up to 100 thousand km) of vascular systems - lymphatic, venous, arterial. Imagine: When you load your body, you need to dramatically increase the bloodstream, oxygen consumption, etc. Heart should work in one moment!
The heart is formed from a variety of cross-striped muscle - myocardiacovered with a serous two-layer shell: a layer adjacent to the muscle - epicard; and an outer layer attaching a heart to neighboring structures, but allowing it to shrink, - pericardium.
Anatomy of the conductive heart system
Muscular partition divides the heart longitudinally on the left and right half. Valves share each half into two cameras: Upper (atrial) and lower (ventricle). So the heart like Four-chamber muscular pump
consists of four cameras separated in pairs fibrous valvesthat allow blood to pass only in one direction
. These cameras include and from them blood vesselsThrough which blood makes a circuit.
Four heart chambers lined with a layer of elastic fabric - endocardium- form two atrium and two ventricle. Left atrium reported with left ventricle with mitral valve, and the right atrium reported with the right ventricle with the help three-stranded valve.
Two hollow veins fall into the right atrium, and in the left - four pulmonary veins. From right ventricle, pulmonary artery leaves, and from the left - aorta. The flow of blood in the heart is constantly and unhindered, while the blood yield from the ventricles in the artery is regulated filuted valveswhich open only when the blood in the ventricle reaches a certain pressure.
The heart works in two types of movements: systolic, or the movement of the reduction, and diastolic, or the movement of relaxation. Reductive reduction nervous systemis not amenable to arbitrary control, as pumping and blood circulation in the body must be continuous.
(Cyclus Cardiacus) - is usually called a blow - a set of electrophysiological, biochemical and biophysical processes occurring in the heart throughout the reduction.
The cycle of the heart activity is made up of three phases:
1. Systoles atrial and diastole ventricles. When reducing the atria, mitral and three-rolled valves opened, and the blood enters the ventricles.
2. SYSTEOLS of the ventricles. Ventricles are reduced by causing an increase blood pressure. The alley valves of the aortic and pulmonary artery open, and the gastrics are emptying through artery.
3. Total diastole. After emptying the ventricles relax, and the heart remains in the rest phase until the blood filling at the atrium is not pressed on the atrioventricular valves.
Reducing, the heart muscle pushes blood first through the atrium, and then through the ventricles.
The right atrium of the heart receives poor blood oxygen on two main veins: the upper hollow and the lower hollow, as well as from the smallest crown sinus, which collects blood from the walls of the heart itself. With the reduction of the right atrium, the blood through a three-rolled valve enters the right ventricle. When the right ventricle is fairly filled with blood, it is reduced and throws blood through pulmonary arteries into a small circle of blood circulation.
Blood enriched with oxygen in the lungs, the lung veins falls into the left atrium. After filling in blood, the left atrium is reduced and pushes blood through the mitral valve in the left ventricle.
After filling the left ventricle, the left ventricle is reduced and the blood is thrown into the aorta with a large force. From the aorta, blood gets into the vessels of a large circle of blood circulation, spreading oxygen to all body cells.
Heart excitation occurs on the conductive heart system - muscle knotted fabric, more precisely, muscle cells specialized on the excitation of the heart muscle. This fabric consists of sinoatrial node(S-A -Zel, sinus knot, kis-flip knot) and atrioventricular node (A-V -Zel, the atrief-ventricular node) located in the right atrium (at the border of atrial and ventricles). In the first of these nodes, electrical impulses arise that cause a reduction of the heart (70-80 contractions per minute). The pulses are then passing through the atrium and excite the second node, which can make the heart (40-60 abbreviations per minute). Through bunch of Gisand fiber Purkinjeexcitement applies to both ventricles, causing them to reduce them. After that, the heart rests until the next impulse, from which a new cycle begins.
The pulses set the heart rhythm (the required frequency), the uniformity and synchronization of the reducing atrial and ventricles in accordance with the activity and needs of the body, the time of day and many other factors affecting a person.
Cardiac pause - a period between auscultatively registered heart tones (Lat. Auscultare listen, listen); The small S.P., corresponding to the ventricular systole, and the greater S.P., corresponding to the diastole of the ventricles.
Valves of heart Act as a gate, giving blood the ability to move from one heart chamber into another and from the heart chambers into the blood vessels associated with them. The heart has the following valves: three-rolled, pulmonary (pulmonary), bivalve (it is mitral) and aortic.
Three-profile valve Located between the right atrium and the right ventricle. When opening this valve, blood passes from the right atrium into the right ventricle. The three-rolled valve prevents the reverse blood flow in the atrium, closing during the reduction of the ventricle. The name of this valve itself says that it consists of three sash.
Valve of the pulmonary artery . With the trilateral valve closed, the blood in the right ventricle finds the output only to the pulmonary trunk. The pulmonary trunk is divided into left and right pulmonary arteries that go according to the left and right lung. The entrance to the pulmonary barrel is closed with a pulp. The pulmonary valve consists of three sash, which are open at the moment of reducing the right ventricle and closed at the time of its relaxation. The pulmonary valve allows blood to fall from the right ventricle into pulmonary arteries, but prevents the blood flow from the pulmonary arteries into the right ventricle.
Bivalve or mitral valve Regulates blood flow from left atrium to left ventricle. Like a three-rolled valve, a double valve closes at the time of reducing the left ventricle. Mitral valve Consists of two sash.
Aortic valve It consists of three sash and covers an entrance to the aorta. This valve skips blood from the left ventricle at the time of its reduction and prevents the reverse current of blood from the aorta to the left ventricle at the time of relaxation of the latter.
Meals and breathing of the heart itself provide coronary (corneous) vessels
Left coronary artery
Begins from the left back sine Wilsalva, heads down to the front longitudinal furrow, leaving the right of itself the pulmonary artery, and on the left - the left atrium and surrounded by a fatty tissue, which usually covers it. It is a wide, but short barrel length is usually not more than 10-11 mm.
Left coronary artery is divided into two, three, in rare cases for four artery, of which the greatest value For pathology, anterior descending (PMW) and envelope branches (s), or artery.
Anterior downward artery is a direct continuation of the left coronary. According to the anterior longitudinal cardiac furrow, it is heading towards the region of the heart of the heart, usually reaches it, sometimes driving through it and goes to the rear surface of the heart.
From the downward artery, a slightly smaller side branches are departed from a sharp corner, which are sent along the front surface of the left ventricle and can reach the blunt edge; In addition, numerous septal branches are deployed from it, trying myocardium and branching in the front 2/3 of the interventricular partition. The side branches feed on the front wall of the left ventricle and give branches to the front papillary muscle of the left ventricle. The upper septal artery gives a twig to the front wall of the right ventricle and sometimes to the front papillary muscle of the right ventricle.
Throughout the front, the leading branch lies on myocardium, sometimes plunging into it with the formation of muscle bridges with a length of 1-2 cm. Otherwise, the front surface of it is covered with fatty tissue of epicardia.
The envelope branch of the left coronary artery usually departs from the latter at the very beginning (the first 0.5-2 cm) at the angle close to the direct, passes in the transverse furrow, reaches the stupid edge of the heart, envelopes it, goes to the back wall of the left ventricle, sometimes reaches The rear interventricular furrow and in the form of the rear downward artery is sent to the top. Numerous branches are deployed from it to the front and rear papillary muscles, the front and rear walls of the left ventricle. It also departs one of the arteries that feed the synoyauricular node.
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Right coronary artery
begins in the front sine Vilsalva. First, it is deep in adipose tissue to the right of the pulmonary artery, envelopes the heart on the right atrioventricular furrow, goes to the rear wall, reaches the rear longitudinal furrow, then in the form of the back of the downward branch drops to the top of the heart.
Artery gives 1-2 branches to the front wall of the right ventricle, partly to front department partitions, both papillary muscles of the right ventricle, the rear wall of the right ventricle and the rear interventricular septum department; From it also departs the second branch to the synoyauricular node.
Highlight three main types of myocardial blood supply
: Medium, left and right.
This unit is based mainly on variations in the blood supply to the rear or diaphragmal surface of the heart, since the blood supply to the front and side departments is quite stable and not subject to significant deviations.
For average type All three main coronary artery are well developed and evenly uniform. The blood supply to the left ventricle is entirely, including both papillary muscles, and the front 1/2 and 2/3 of the interventricular partition is carried out through the system of the left coronary artery. Right ventricle, including both right papillary muscles and rear 1 / 2-1 / 3 partitions, gets blood from the right coronary artery. This, apparently, the most common type of blood supply to the heart.
For left type The blood supply to the entire left ventricle and, in addition, the entire partition and partially the rear wall of the right ventricle is carried out due to the developed envelope branch of the left coronary artery, which reaches the back longitudinal furrow and ends here in the form of a rear downward artery, giving part of the branches to the rear surface of the right ventricle .
Right type It is observed with a weak development of the envelope branch, which or ends, not reaching the stupid edge, or goes into the coronary artery of the stupid edge, without turning to the rear surface of the left ventricle. In such cases, the right coronary artery after the reverse of the rear downstream artery usually gives a few more branches to the rear wall of the left ventricle. At the same time, all right ventricles, back wall Left ventricle, rear left papillary muscle and partially the top of the heart get blood from the right coronary arteriole.
Myocardine blood supply is carried out directly
:
a) capillaries lying between muscle fibers with the powered and receiving blood from the system coronary arteries through arterioles;
b) a rich network of myocardial sinusoids;
c) vessels of Viesan-tebezia.
With the increase in pressure in coronary arteries and an increase in the work of the heart, blood flow in coronary arteries is increasing. The lack of oxygen also leads to a sharp increase in the coronary blood flow. Sympathetic and parasympathetic nerves, apparently, weakly influence the coronary artery, providing basic effects directly on the heart muscle.
The outflow occurs through veins going to the coronary blue
Venous blood in the coronary system is collected in large vessels, usually located near the coronary arteries. Some of them merge, forming a large venous canal - a coronary sine, which runs along the rear surface of the heart in a groove between the atria and ventricles and opens into the right atrium.
Interboronary anastomoses play an important role in coronary blood circulation, especially in the context of pathology. Anastomoses are more in the hearts of persons suffering ischemic diseaseTherefore, the closure of one of the coronary arteries is not always accompanied by necrosis in myocardium.
IN normal hearts Anastomoses were found only in 10-20% of cases, with a small diameter. However, the amount and the amount of them increase not only when coronary atherosclerosis, but also with valve heart defects. Age and half of themselves no effect on the presence and degree of development of anastomoses do not provide.
Heart has its own stem cells
06/01/2006. Computer Scatter №46.
Previously, experts believed that independent restoration of the heart is impossible, since the developed cells of this body are not divided. However, in 2003, the NEW Scientist reports, researchers from Laboratory Piero Anversals from Medical College in Valhalle (New York, USA) found stem cells in mice heart fabrics. Before today's day Scientists could not say for sure whether these cells are present in the heart constantly or migrate from other tissues, such as bone marrow.
A response to this question has been engaged in the colleague insight, Annarozoz Lerie. She tried to find in the heart of the so-called "niches" for stem cells. "Niche", where stem and mature cells are grouped, found between heart muscle cells
. Having done this discovery, Lerie and her staff held a number of experiments. Scientists were withdrawn non. a large number of heart stem cells in people who moved the heart surgery, grown them in laboratory conditions And transplanted into damaged hearts of mice and rats.
The results of Leri experiments call promising and believes that the use of stem cells of the heart in the treatment of heart disease can be much more efficient than the use of stem cells derived from bone marrow. Now the main task of researchers is to find out how heart stem cells work, which regulates their activities and how this mechanism can be imitated.
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A group of physicists from the University of Boston, headed by Yosef Ashkenazy (Yosef Ashkenazy) in detail investigated the patterns of cardiac rhythm.
Widely used electrocardiogram
It helps to analyze only general characteristics Heartbeat, however, does not take into account the rhythmic pattern of heart blows - that is, the exact sequence of its blows and pauses.
Ashkenazi and his colleagues developed a computer algorithm, allowing more deeply to penetrate heart secrets. Calculations showed that temporary the intervals between heart blows are rarely the same
. That is, the heartbeat is more like a virtuoso strike of the drums, than on a uniform clock ticking.
According to scientists, a healthy heart is working like an xopold drummer. In general, the musician holds rhythm, but from time to time deliberately admits small failures. Since it hits the drum pretty quickly, acceleration or delay is almost indistinguishable for rumor, but the parties give a special charm. This is the case with a heart - it constantly "improvises." It is curious that some rhythmic pattern chaotic characteristic is precisely for a healthy heart.
. In people who are in preinfarction state, the heartbeat rhythm becomes mechanically accurate.
Conclusions about the work of the Heart of Ashkenazi did, analyzing the tape records of the "Music" of the heart. Then he explored the heart rhythm of 18 healthy and 12 sick people - mostly suffering from thrombus in the vessels of the heart - and was finally convinced of the correctness of their calculations.
Ashkenazi argues that his work will allow to diagnose not only already evolved heart disease, but also a predisposition to them.
The article is published in Physical Review Letters.
Run, rabbit, run
Everyone knows that lying on the sofa more harmful walks and physical education. And why? Scientists of the Institute figured out clinical cardiology. I planted rabbits in close cells (almost in the size of the body) and kept 60 days without a movement. Then we looked at their hearts under electron microscope. Saw a terrible picture. Many miofibrils - Fibers, thanks to which the muscle is reduced, - atrophied. The relationship between cells that help them work is cooled. The changes affected the nerve endings controlling muscles. The walls of the capillaries carrying blood began to grow inside, reducing the clearance of vessels. Here you and the sofa!
Why people love Petrosyan and to
Dr. Michael Miller from the University of Maryland and his colleagues held a series of experiments, showing volunteers two films: cheerful and sad. And at the same time they tested their hearts and blood vessels. After the tragic film in 14 out of 20 volunteers of blood flow in vessels
decreased by an average of 35%
. And after funny, on the contrary, increased by 22% In 19 of the 20 subjects.
Changes in vessels in launched volunteers were similar to those arising during aerobic classes. But at the same time they did not have any pain in the muscles, no fatigue and overvoltage, which often accompany great physical exertion. Scientists concluded: Laughter reduces the risk of cardiovascular diseases.
Syndrome of the broken heart
Such a new diagnosis appeared in cardiology. For the first time it was described 12 years ago by Japanese doctors. Now it was recognized in other countries. The syndrome arises, as a rule, in women older than forty, who experienced a love failure. The cardiogram and ultrasound show them the same violations as with a heart attack, although the coronary vessels are in order. But stress hormone level - adrenaline
, For example, they are 2-3 times higher than in infarction patients. And in comparison with healthy it is exceeded at 7-10, and in some cases even 30 times!
It is the hormones that doctors consider "beat" to the heart, forcing it to react with classical symptoms of a heart attack: pain beyond the sternum, liquid in the lungs, acute heart failure. Fortunately, patients with new syndrome are pretty quickly restored if they are treated correctly.
Chocolate is useful for the heart
06/01/2004. Membrana.
The daily use of small portions of chocolate favorably affects the work of blood vessels in the body, which, in turn, is very good for the health of the heart.
To this conclusion, a group of doctors came from University of California to San Francisco (University of California, San Francisco). True, such an action has not any chocolate, but only the one in the process of producing which, a large amount of flavonoids contained in cocoa
.
The team led by Mary Enlarler (Mary Engler) studied for two weeks of 21 people who were chosen randomly. All of them during the experiment ate chocolate is the same in appearance. But part of the tiles was rich in flavonoids, and the other - on the contrary, almost did not contain these substances. Naturally, volunteers testes did not know what kind of tile variant they are issued. Scientists spent ultrasound examination The shoulder artery is the volume of blood flow in it and the ability of the vessel walls to expand and shrink. It turned out that those who used chocolate with flavonoids, these parameters have improved in about two weeks by about 13%.
New job (09/30/2004) Dr. Charalambos Vlachopoulos (Charalambos Vlachopoulos) from Athens University (University of Athens) adds points to a popular dessert. Dark chocolate (but not dairy) improves blood flow and reduces the risk of blood clots, capable of clinging the vessels, asserts the Athenian researcher. The results of the study showed an improvement in the functioning of the endothelium - a thin layer of cells on inner side vessels. In addition, the survey of volunteers showed that chocolate protects the body from the devastating effect of the so-called free radicals.
Eyes - heart mirror
06/09/2006. Overtorniy Portal
Adjunct-professor TIN WONG, from the University Center for Eye Study (Melbourne, Australia) received a reward of the Commonwealth countries for achievements in the field of healthcare and medical research.
Such a high award he was awarded for the development eye diagnosiswhich will help in identifying a number of heart and other serious diseases.
A group of Professor Wong for five years spent a lot of work on more than 20 thousand patients. Scientists have developed and brought to clinical practice a technique that helps measure the degree of narrowing of small blood vessels of the eye, which gives a signal about the start of development of various diseases.
Cardiac cycle: essence, physiology, flow and phase normally, hemodynamics
In order to understand how they appear and are treated, certain cardiology diseases, any medical student and especially the doctor should know the foundations of the normal physiology of cardiovascular vascular system. Sometimes it seems that the heartbeat is based on simple reductions of the heart muscle. But in fact, more complex electro-biochemical processes are laid in the cardiac rhythm mechanism, leading to the emergence of mechanical work smoothly muscular fibers. Below we will try to figure out what supports regular and uninterrupted heart abbreviations throughout the human life.
Electro-biochemical backgrounds of cardiac activity starts to be laid in the intrauterine period, when the fetus is formed intracardiac structures. Already in the third month of pregnancy, the child's heart has a four-chamber basis with an almost complete formation of intracardiac structures, and it is from this point on that the full heart cycles are carried out.
To make it easier to understand all the nuances of the heart cycle, it is necessary to determine such concepts as phases and duration of heart abbreviations.
Under the heart cycle, one complete abbreviation of myocardium is understood, in the process of which a sequential change is carried out during a certain period of time:
- SYSTEOLOCOM SYSTEM
- Systolic reduction of ventricles,
- General diastolic relaxation of the entire myocardium.
Thus, for one heart cycle, or for one complete heart reduction, the entire volume of blood, which is in the gastric cavity, pushes large vessels from them - into the lumen of the aorta on the left and the pulmonary artery on the right. Due to this, in continuous mode, the blood is obtained all internal organs, including a brain (a large circulation circle - from aorta), as well as the lungs (a small circle of blood circulation - from the pulmonary artery).
Video: Heart Reduction Mechanism
How long does the cardiac cycle last?
The normal duration of the time cycle time is specified genetically, while remaining almost the same for human organismbut at the same time can vary within the normal range different persons. Usually the duration of one complete heart abbreviation make up 800 MilisecundsIn which the atria (100 Milicec) decreases (100 Milice), reduction of ventricles (300 Miliceca) and the relaxation of cardiac cameras (400 Miliceca). At the same time, the heart rate in a calm state is from 55 to 85 shots per minute, that is, the heart per minute is able to carry out the specified number of cardiac cycles. The individual duration of the heart cycle is calculated by the formula CSS: 60..
What happens during the heart cycle?
cardiac cycle from a bioelectric point of view (the impulse is born in sinus node and applies to heart)
The electrical mechanisms of the cardiac cycle include the functions of automatism, excitation, conducting and contractility, that is, the ability to generate electricity in myocardial cells, to carry out electrically active fibers further, as well as the ability to respond to a mechanical reduction in response to electrical excitation.
Thanks to complex mechanisms Throughout a person's life, the ability of the heart is maintained correctly and regularly shrink, at the same time subtly reacting to constantly changing conditions ambient. For example, systoles and diastites occur faster and more actively if a person threatens danger. At the same time, under the influence of adrenaline's adrenaline, the ancient, the evolutionarily established principle of three "b" - Bay, be afraid, run, to perform a greater blood supply to the muscles and the brain, which, in turn, is directly dependent on activity of cardio-vascular system, in particular, from accelerated alternation of the phases of the cardiac cycle.
hemodynamic Reflection of the Heart Cycle
If we talk about hemodynamics (blood promotion) across the heart cameras during a complete heart rate, then it is worth noting the following features. At the beginning of the heart rate after the electrical excitation of the atrial muscle cells is obtained, biochemical mechanisms are involved in them. Each cell is myofibrils from mosicine and actin proteins, which, under the influence of microtons of ions in the cell and from the cell, begin to decline. The combination of contractions of myofibrils leads to a reduction in the cell, and the aggregate of muscle cells is to reduce the entire cardiac chamber. At the beginning of the heart cycle, atrium is reduced. In this case, blood, by discovering atri-ventricular valves (tricuspid to the right and mitral left), enters the cavity of the ventricles. After the electrical excitation spread on the walls of the ventricles, systolic reduction of ventricles occurs. Blood is expelled in the above vessels. After the height of blood from the gastric cavity comes total diastole Hearts, while the walls of cardiac cameras are relaxed, and cavities are passively filled with blood.
Heart cycle phases normal
One full-fledged heart abbreviation is made up of three phases, called the systreard systole, the systole of the ventricles and the total diastology of the atrial and ventricles. Each phase has its own characteristics.
First phasethe heart cycle, as already described above, is the power of blood into the cavity of the ventricles, for which it is necessary to open atre-ventricular valves.
Second phase The heart cycle includes periods of voltage and expulsion, while in the first case there is an initial reduction in muscle cells of ventricles, and in the second - blood is influenced into the lumen of the aorta and the pulmonary barrel, followed by progress of blood in the body. The first period is divided into asynchronous and isoovolumenic contractile types, while muscle fibers of the myocardial of ventricles are reduced separately, and then in synchronous manner, respectively. The expulsion period is also divided into two types - rapid exile of blood and slow exile of blood, in the first case, the maximum blood volume is released, and in the second - not such a significant volume, since the remaining blood moves into large vessels under the influence of a minor pressure difference between the cavity of the ventricles and aortic lumen (pulmonary trunk).
Third phase, It is characterized by rapid relaxation of muscle ventricular cells, as a result of which the blood is quick and passively (also under the action of the pressure gradient between the filled beans of the atrium and "empty" ventricles), begins to fill the latter. As a result, cardiac chambers are filled with blood volume sufficient for the next cardiac output.
Heart cycle with pathology
Many pathological factors can affect the duration of the heart cycle. So, in particular, the accelerated rhythm of heart abbreviations due to a decrease in the time of one heart abbreviation occurs during fever, intoxication of the body, inflammatory diseases internal organs, P. infectious diseases, P. shock conditionsas well as in injuries. The only physiological factor capable of causing the shortening of the heart cycle is physical exertion. In all cases, a decrease in the duration of one full heart abbreviation is due to the growing need of organism cells in oxygen, which is provided by more frequent heart abbreviations.
The elongation of the duration of the heart rate, leading to a decrease in the heart rate, occurs in violation of the work of the conductive heart system, which, in turn, is clinically manifested by arrhythmias according to the type of bradycardia.
How can I appreciate the heart cycle?
Directly the fullness of one full heart abbreviation is quite possible to investigate and evaluate using functional diagnostic methods. The "golden" standard in this case is that allows you to register and interpret such indicators as a shock volume and fraction of emissions constituting in a normal blood of blood for one cardiac cycle, and 50-75%, respectively.
In this way, normal work Hearts are provided by continuous alternation of the phases of cardiac abbreviations that consistently replacing each other. If there are any deviations in the normal physiology of the Cardiac cycle, develop. As a rule, this is a sign of increasing, and in both cases suffers. So in order to know how to treat these types of heart dysfunction, and it is necessary to clearly understand the foundations normal cycle Heart activities.
Video: Heart cycle lectures
Heart cycle - This systole and diastole hearts, periodically repeated in strict sequence, i.e. A period of time comprising one reduction and one relaxation of atrial and ventricles.
In the cyclical functioning of the heart, two phases are distinguished: systole (reduction) and diastole (relaxation). During the systole of the heart cavity is exempted from the blood, and during diastoles are filled. The period comprising one systole and one diastole atrial and ventricles and the following common pause is called cardiac cycle.
Atrial systoles in animals lasts 0.1-0.16 s, and ventricular systoles - 0.5-0.56 p. The overall pause of the heart (simultaneous diastole atrial and ventricles) lasts 0.4 s. During this period, the heart rests. The entire cardiac cycle continues for 0.8-0.86 p.
Atrial work is less complicated than the work of the ventricles. Atrial systole provides blood flow in the ventricles and lasts 0.1 s. The atrium is then moving to the diastole phase, which continues for 0.7 s. During the atrium diastole is filled with blood.
The duration of various phases of the cardiac cycle depends on the frequency of heart abbreviations. With more frequent heart contractions, the duration of each phase, especially diastole, is reduced.
Heart cycle phases
Under Heart cycle Understand the period covering one reduction - Systole And one relaxation - diastoleu Atrial and ventricles are a common pause. The total duration of the heart cycle at the frequency of cardiac abbreviations 75 ° C / min is 0.8 s.
Reduction of the heart begins with atrial systole lasting 0.1 s. Atrial pressure at the same time rises to 5-8 mm Hg. Art. Atrial systoles is replaced by the ventricular systole lasting 0.33 s. Stomach systoles are divided into several periods and phases (Fig. 1).
Fig. 1. Heart cycle phases
Voltage period It lasts 0.08 C and consists of two phases:
- the phase of asynchronous reduction of the myocardium of ventricles - lasts 0.05 s. During this phase, the process of excitation and the next process of the reduction is distributed by the myocardium of ventricles. Pressure in the ventricles is still close to zero. By the end of the phase, the reduction covers all the fibers of myocardium, and the pressure in the ventricles begins to increase quickly.
- the isometric reduction phase (0.03 s) - begins with slamming of the sashing and ventricular valves. At the same time, I, or systolic, tone of the heart occur. The displacement of the leaf and blood towards the atrium causes rise to the rise in atrial pressure. Pressure in the ventricles rapidly increases: up to 70-80 mm Hg. Art. in the left and up to 15-20 mm Hg. Art. In the right.
Foldy I. alley valves Even closed, the volume of blood in the ventricles remains constant. Due to the fact that the liquid is almost incompressible, the length of the fibers of myocardium does not change, only their voltage increases. The blood pressure in the ventricles is growing rapidly. The left ventricle quickly acquires a round shape and with power hits interior surface Breast wall. In the fifth intercole, 1 cm on the left of the middle-hearth line at this moment is determined by the top push.
By the end of the voltage period, the rapid pressure in the left and right ventricles becomes higher than the pressure in the aorta and the pulmonary artery. Blood from the ventricles rushes into these vessels.
Exile period Blood from the ventricles lasts 0.25 s and consists of a phase of the rapid (0.12 C) and the phase of slow expulsion (0.13 s). Pressure in the ventricles is growing: in the left up to 120-130 mm Hg. Art., and in the right up to 25 mm Hg. Art. At the end of the phase of slow expulsion, the myocardians of the ventricles begins to relax, its diastole comes (0.47 s). The pressure in the ventricles drops, blood from the aorta and the pulmonary artery is rushed back into the cavity of the ventricles and "slams" the semi-lunk valves, while the II, or diastolic, tone of the heart occur.
Time from the beginning of the relaxation of ventricles to the "slamming" of the semi-luncture valves is called protodiastolic period (0.04 s). After slaving the semi-lunged valves, the pressure in the ventricles falls. Folded valves at this time are still closed, the amount of blood remaining in the ventricles, and therefore the length of the myocardial fibers do not change, so this period is called the period Isometric relaxation (0.08 s). By the end, its pressure in the ventricles is becoming lower than in the atria, the atrocaded-ventricular valves and blood from the atrium enters the ventricles. Begins The period of filling the ventricles with bloodwhich lasts 0.25 s and is divided into the rapid phases (0.08 s) and slow (0.17 seconds) filling.
The oscillation of the walls of the ventricles due to the rapid flow of blood to them causes the appearance of the III tone of the heart. By the end of the phase of slow filling, the systole atrial systole occurs. The atrium is injected into the ventricles additional amount of blood ( presistic periodequal to 0.1 s), after which a new cycle of ventricular activity begins.
The oscillation of the walls of the heart, caused by the reduction of the atria and the additional flow of blood in the ventricle, leads to the appearance of the IV of the heart.
With the usual listening of the heart, loud I and II tones are well heard, and the quiet III and IV tons are detected only during graphical registration of the tones of the heart.
A person has a number of heart abbreviations per minute can significantly fluctuate and depends on various external influences. While doing physical work Or a sports load heart can be reduced to 200 times per minute. At the same time, the duration of one cardiac cycle will be 0.3 s. The increase in the number of heart abbreviations is called Tachycardia, In this case, the cardiac cycle decreases. During sleep, the number of heart abbreviations decreases to 60-40 beats per minute. In this case, the duration of one cycle is 1.5 s. Reducing the number of heart abbreviations call BradycardiaAt the same time, the heart cycle increases.
Structure of the heart cycle
Heart cycles follow the frequency set by the driver of the rhythm. The duration of a single cardiac cycle depends on the frequency of heart cuts and, for example, at a frequency of 75 ° C / min, it is 0.8 s. The general structure of the heart cycle can be represented as a schema (Fig. 2).
As can be seen from fig. 1, with the duration of the cardiac cycle of 0.8 s (cutting frequency 75 ° C / min), the atrium is in a state of systole 0.1 s and in a diastole state of 0.7 s.
Systole - the phase of the heart cycle, including the reduction of myocardium and the exile of blood from the heart into the vascular system.
Diastole - Heart cycle phase, including the relaxation of myocardium and filling the heart cavities with blood.
Fig. 2. Scheme common Structure cardiac cycle. Dark squares showing systole atrial and ventricles, light - their diastoles
The ventricles are in a state of systole about 0.3 s and in a state of diastole about 0.5 s. At the same time in a state of atrium diastole and ventricles are about 0.4 s (general diastole heart). Systole and ventricular diastole are divided into periods and phases of the cardiac cycle (Table 1).
Table 1. Periods and phases of the heart cycle
Phase asynchronous cut - The initial stage of systole, in which the excitation wave applies to the myocardium of the ventricles, but the pressure in the ventricles is absent and the pressure in the ventricles is absent - from 6-8 to 9-10 mm RT. Art.
Phase isometric cut - The stage of systole, in which the closure of atrioventricular valves and the pressure in the ventricles is rapid up to 10-15 mm Hg. Art. In the right and up to 70-80 mm Hg. Art. in the left.
Fast Exile Phase - Stage systole, in which an increase in ventricular pressure is observed to maximum values \u200b\u200b- 20-25 mm Hg. Art. In the right and 120-130 mm Hg. Art. In the left and blood (about 70% of systolic emissions) enters the vascular system.
Phase slow expulsion - Stage systole, in which blood (the remaining 30% systolic ejection) continues to flow into the vascular system at a slower rate. The pressure is gradually decreasing in the left ventricle from 120-130 to 80-90 mm RT. Art., in the right - from 20-25 to 15-20 mm RT. Art.
Protodiastolic period - Transition period from systole to diastole, in which ventricles begin to relax. The pressure is reduced in the left ventricle to 60-70 mm Hg. Art., in the temper - up to 5-10 mm RT. Art. By virtue of greater pressure in the aorta and pulmonary artery, the semi-short valves close.
Period of isometric relaxation - The diastole stage, in which the gastric cavities are insulated with closed atrioventricular and semi-lounge valves, they areometrically relaxed, the pressure is approaching 0 mm RT. Art.
Fast Filling Phase - The diastole stage, in which the opening of atrioventricular valves and blood at high speed rushes into the ventricles.
Slow filling phase - The diastole stage in which the blood slowly enters the atrium and through the open atrioventricular valves in the ventricles. At the end of this phase, the ventricle is 75% filled with blood.
Presistic period - The stage of the diastole coinciding with the systreard systole.
SISTOMS OF SISTRADA - Reducing the muscles of atria, in which the pressure in the right atrium increases to 3-8 mm RT. Art., in the left - up to 8-15 mm Hg. Art. And about 25% of the diastolic volume of blood flows into each of the ventricles (15-20 ml).
Table 2. Cardiac phase characteristics
The abbreviation of the myocardium atrial and ventricles begins after their excitation and since the rhythm driver is located in the right of atrium, its potential is initially applied to myocardium right and then the left atrial. Consequently, myocardium right atrium responds with excitation and reduction of a little earlier than myocardium left atrium. IN normal conditions The heart cycle begins with the atrial systole, which continues 0.1 s. The ambulance with the excitation of the myocardium of the right and left atriality is reflected in the formation of the teeth into the ECG (Fig. 3).
Even before the atrium systole, the AV valves are in the open state and the cavity of the atrial and ventricles is already largely filled with blood. Degree of stretching the thin walls of the myocardium atrial blood is important for irritation of the mechanoreceptors and the production of the atriological sodium-eptic peptide.
Fig. 3. Changes in heart performance in various periods and heart cycle phases
During the atrial systole, the pressure in the left atrium can reach 10-12 mm Hg. Art., and in the right - up to 4-8 mm Hg. Art., Atrialia additionally fill the gastrics with blood volume, constituting about 5-15% of the volume by this time in the ventricles. The volume of blood entering the ventricles in the atrium systole, during exercise may increase and make up 25-40%. The volume of additional filling is able to increase to 40% and more people over 50 years old.
The flow of blood under pressure from the atria helps to stretch the myocardial of ventricles and creates conditions for their more effective subsequent reduction. Therefore, atrium plays the role of a peculiar amplifier of the contractile capacity of the ventricles. With this feature function (for example, clear arrhythmia) The efficiency of ventricular work decreases, the reduction of their functional reserves is developing and the transition to the insufficiency of the myocardial contractual function is accelerated.
At the time of the atrial systole, a-wave is recorded on the curve of the bullet, in some people when recording phonocardiograms, the 4th tone of the heart can be recorded.
The volume of blood, which is after the atrial systole in the cavity of the ventricles (at the end of their diastole), is called of course-diastolic.It consists of blood volume remaining in the ventricle after the previous systole ( of course systolic Volume), blood volume that filled the bustling of the ventricle during its diastole to the atrial systole, and the additional volume of blood entered into the ventricle in the atrodi systole. The magnitude of the finite-diastolic volume of blood depends on the size of the heart, the volume of blood flushed from the veins and a number of other factors. In healthy young man In a state of rest, it can be about 130-150 ml (depending on the age, gender and body weight can be fluent in 90 to 150 ml). This blood volume increases the pressure in the ventricular cavity, which during the atrium systole becomes equal to pressure in them and can fluctuate in the left ventricle within 10-12 mm Hg. Art., and in the right - 4-8 mm Hg. Art.
Over the interval of 0.12-0.2 s, the corresponding interval PQ.on the ECG, the action potential from the CA node is distributed to the top of the ventricles, in the myocardium of which the process of excitation begins, quickly propagating in directions from the top to the base of the heart and from the endocardial surface to epicardial. Following the excitation, a reduction in myocardium or ventricular systoles begins, the duration of which also depends on the frequency of heart cuts. In peace conditions, it is about 0.3 s. Stomach Systole consists of periods Voltage(0.08 s) and exile (0.25 s) blood.
Systole and diastole of both ventricles are carried out almost simultaneously, but flow in various hemodynamic conditions. Further, more detailed description Events flowing during systole will be treated with the example of the left ventricle. For comparison, some data for the right ventricle are given.
The voltage period of the ventricles is divided into phases Asynchronous (0.05 s) and isometric (0.03 c) Reduction. The short-term phase of asynchronous reduction at the beginning of the systole of the myocardial of the ventricles is a consequence of non-use of the coverage of the excitation and reduction of various departments of myocardium. Excitation (corresponds to the teeth Q. On the ECG) and the reduction of myocardium arises initially in the area of \u200b\u200bthe papillary muscles, the top part of the interventricular partition and the tops of the ventricles and during about 0.03 s applies to the remaining myocardium. It coincides with time with registration on the ECG Q.and ascending part of the teeth R.up to its vertex (see Fig. 3).
The top of the heart is reduced before its base, therefore the top of the ventricles is pulled in the direction of the base and pushes the blood in the same direction. Involuted by the excitation area of \u200b\u200bthe myocardium of ventricles at this time may be slightly stretched, therefore the volume of the heart is practically not changed, blood pressure in the ventricles does not change significantly and remains lower than blood pressure in large vessels over the three-rolled valves. The blood pressure in the aorta and other arterial vessels continues to fall, approaching the value of the minimum, diastolic pressure. However, the three-grained vascular valves remain closed while.
Atrialia at this time relaxes and blood pressure in them decreases: for the left atrium, on average with 10 mm Hg. Art. (presets) up to 4 mm Hg. Art. By the end of the phase asynchronous reduction of the left ventricle, blood pressure in it increases to 9-10 mm Hg. Art. Blood, experiencing pressure from the cutting upper part of myocardial, picks up the flaps of the AV valves, they are closed, taking a position close to horizontal. In this position, the sash is held by tendon threads of nobble muscles. The shortening of the heart sizes from its top to the base, which, due to the invariabilities of the sizes of tendral threads, could lead to the turning out of the valve flaps in the atrium, is compensated by the reduction of the puffy muscles of the heart.
At the time of closing atrioventricular valves listens 1-y. systolic tone Hearts ends with an asynchronous phase and the isometric reduction phase begins, which is also called the phase of isoovolumenic (isoisolum) reduction. The duration of this phase is about 0.03 s, its implementation coincides with the time interval in which the downward part of the teeth is registered R. And the beginning of the priest S. on ECG (see Fig. 3).
From the moment of the closure of Av-valves under normal conditions, the cavity of both ventricles becomes hermetic. Blood, like any other liquid, is incompressible, therefore the reduction of myocardial fibers occurs with their unchanged length or in isometric mode. The volume of ventricular cavities remains constant and the reduction in myocardium occurs in isozyolum. The increase in the voltage and strength of the reduction of myocardium in such conditions is converted into a rapidly growing blood pressure in the cavities of the ventricles. Under the influence of blood pressure on the AB region, the partition occurs a short-term shift towards the atria, transmitted by flowing venous blood And it is reflected in the appearance on the curve of the Bureau of the C-wave. For a short period of time - about 0.04 with blood pressure in the left ventricle cavity reaches the value comparable to its value at this point in the aorta, which decreased to the minimum level - 70-80 mm RT. Art. Blood pressure in the right ventricle reaches 15-20 mm Hg. Art.
Exceeding blood pressure in the left ventricle over the size of the diastolic pressure of blood in the aorta is accompanied by the discovery of the aortic valves and the change in the myocardial voltage period by the blood expulsion period. The reason for the discovery of the semi-lunged vessel valves is the blood pressure gradient and the pocket feature of their structure. The flaps of the valves are pressed against the walls of the blood flow of the blood exhausted in them with ventricles.
Exile period blood lasts about 0.25 s and is divided into phases Quick Exile (0.12 s) and Slow Exile blood (0.13 s). During this period, the AV valves remain closed, durable - open. The rapid exile of blood at the beginning of the period is due to a number of reasons. From the beginning of the excitation of cardiomyocytes, about 0.1 ° C passed and the potential of action is in the plateau phase. Calcium continues to enter the cage through open slow calcium channels. Thus, the myocardial fibers of myocardium continues to increase the high voltage for the beginning of the exile. Myocardium with more power continues to squeeze the decreasing blood volume, which is accompanied by a further increase in the pressure of the ventricular cavity. The blood pressure gradient between the cavity of the ventricle and the aorta increases and the blood at high speed begins to be expelled in the aorta. In the phase of rapid exile in the aort, more than half of the impact volume of blood expedited from the ventricle for the entire expulsion period (about 70 ml) is ejected. By the end of the phase of the rapid exile of blood pressure in the left ventricle and in the aorta reaches its maximum - about 120 mm Hg. Art. In young people in a state of rest, and in the pulmonary trunk and right ventricle - about 30 mm Hg. Art. This pressure is called systolic. The phase of the rapid exile of blood is carried out in a period of time when the end of the teeth is recorded on the ECG S. and isoelectric part of the interval St. before the start of the priest T. (See Fig. 3).
Subject to rapid expulsion of even 50% of the impact volume of blood flow in the aorta for a short time will be about 300 ml / s (35 ml / 0.12 s). The average rate of blood outflow from the arterial part of the vascular system is about 90 ml / s (70 ml / 0.8 s). Thus, more than 35 ml of blood flows in the aort of 0.12 s, and during the same time it flows from about 11 ml of blood to the artery. Obviously, to accommodate for a short time of a flowing larger blood compared to the subject, it is necessary to increase the tank of the vessels taking this "excess" blood volume. Part of the kinetic energy of the cutting myocardium will be spent only on the exile of blood, but also on the stretching of the elastic fibers of the wall of the aorta and large arteries to increase their container.
At the beginning of the rapid range of blood, the stretching of the walls of the vessels is carried out relatively easily, but as it is exposed to more blood and an increasing stretch of vessels is growing with stretching. The limit of stretching elastic fibers and stretching is beginning to expose rigid collagen fibers of vessel walls. The blood pressure is preventing the resistance of peripheral vessels and blood itself. Myocardium must be spent on overcoming these resistances a large amount of energy. The potential energy of the muscular tissue and the elastic structures of the myocardium itself is exhausted and the strength of its reduction is calculated in the phase of isometric voltage.
The height of blood begins to decrease and the rapid expulsion phase is replaced by the phase of the slow expulsion of the blood, which is also called phase reduced expulsion. Its duration is about 0.13 s. The rate of reduction of ventricular volume decreases. The blood pressure in the ventricle and in the aorta at the beginning of this phase decreases with almost the same speed. By this time there is a slower closure calcium canals, Ends the phase of the potential of the action potential. Calcium input to cardiomyocytes decreases and the membrane of myocytes enters the phase 3 - finite repolarization. Systole is completed, the period of blood islaring and the diastole of the ventricles begins (corresponds to the time phase 4 of the action potential). The implementation of reduced expulsion occurs in a period of time when the ECG is registered T., and the completion of systole and the beginning of the diastole is at the time of the end of the teeth T..
In the Systole of the ventricles of the heart, more than half of the finite-diastolic blood volume (about 70 ml) are expelled. This volume was named Blood shock volume.The impact volume of blood may increase with an increase in the contraction of myocardium and, on the contrary, decrease with its insufficient contractility (see further the indicators of the pump function of the heart and the contraction of myocardium).
Blood pressure in the ventricles at the beginning of the diastole becomes lower than blood pressure in arterial vessels derived from the heart. Blood in these vessels is experiencing the action of the forces of stretched elastic fibers of the walls of the vessels. The lumen of the vessels is restored and some amount of blood outstanding. Part of the blood leaks at the periphery. Another part of the blood is displaced in the direction of the ventricles of the heart, it fills in the reverse movement of pockets of three-risk vascular valves, the edges of which are closed and held in this state the blood pressure drop.
The time interval (about 0.04 s) from the beginning of the diastole before the slamming of the vascular valves is named protodiastic interval.At the end of this interval, the 2nd diastolic head of the heart is recorded and listened. When synchronous ECG records and phonocardiograms, the beginning of the 2nd tone is recorded at the end of the TWE to the ECG.
The diastole of the myocardium of ventricles (about 0.47 (c) is also divided into periods of relaxation and filling, which, in turn, are divided into phases. Since the closure of the semi-short vascular valves of the ventricular cavity becomes 0.08 with closed, since the AV valves are still closed by this time. The relaxation of myocardium, due to the main properties of the elastic structures of its intra and extracellular matrix, is carried out under isometric conditions. In the cavities of the ventricles of the heart remains after systole less than 50% of blood from the finite-diastolic volume. The volume of cavities of the ventricles during this time does not change, the blood pressure in the ventricles begins to decrease quickly and tends to 0 mm Hg. Art. Recall that by this time the blood continued to return for about 0.3 s and the atrial pressure increases gradually. At the time when blood pressure in atrial races exceed the pressure in the ventricles, the opening of the AV valve occurs, the phase of isometric relaxation ends and the period of filling the blood of the ventricles.
The filling period lasts about 0.25 s and is divided into fast and slow filling phases. Immediately after the discovery of the AV valves, the blood according to the pressure gradient quickly comes from the atrium to the cavity of the ventricles. This is facilitated by a certain suction effect of relaxing ventricles associated with their fraud under the influence of the elastic forces arising from the compression of myocardium and its connective tissue frame. At the beginning of the rapid fill phase, sound oscillations in the form of the 3rd diastolic tone of the heart can be recorded on the 3rd diastolic tone of the heart, the reason for the discovery of AV valves and the rapid blood transition to the ventricles.
As the ventricles filling the blood pressure drop between the atria and ventricles decreases and approximately 0.08 from the rapid filling phase is replaced by the phase of slow filling of the ventricles with blood, which lasts about 0.17 p. The filling of the ventricles in the blood in this phase is carried out mainly due to the preservation of residual kinetic energy in moving along blood vessels, led by a previous reduction in the heart.
0.1 C. until the end of the phase of slow filling in the blood of the ventricles, the heart cycle is completed, a new action potential occurs in the rhythm driver, the next atrial systole and ventricles are carried out by filled with finished-diastolic blood volumes. This time period of 0.1 s, completing the heart cycle, is sometimes called yet Period Additional Fill ventricles during the systreard systole.
An integral indicator characterizing mechanical is the volume of blood pumped by the heart per minute, or a minute blood volume (IOC):
IOC \u003d heart rate. Uh,
where the heart rate is the frequency of heart cuts per minute; UO - shock volume of the heart. Normally, at rest, the IOC for a young man is about 5 liters. The regulation of the IOC is carried out by various mechanisms through a change in heart rate and (or) UO.
The effect on the heart rate can be rendered through the change in the properties of the cell rhythm driver. The impact on the UO is achieved through the impact on the reduction of myocardial cardiomyocytes and synchronization of its reduction.
The heart cycle, or the heart's work cycle, is called a sequence of events occurring during a single reduction in the heart. Its duration at 75 heart abbreviations per minute is 0.8 seconds. The heart cycle consists of three phases:
Systole atrial, which lasts 0.1C. During systole, I atrial pressure in them becomes more than in the ventricles, and, - | Because The ventricles at this time are in a relaxed state (in a state of diastole) blood is pushed into them.
Then there comes diastole atrial (0.7 s) and at the same time. Stomach Systole, which continues approximately 0.3 seconds. Pressure in the ventricles is rising, and the blood enters the aorta and the pulmonary artery. Then the diastole of the ventricles occurs, which continues 0.5 seconds.
The time of coincidence of the state of the atrial diastole and ventricles (about 0.4 s) is called a common pause.
Currently, it is believed that the stomach systoles not only contributes to the ejection of blood. When cutting the ventricles, the atrocarditricular partition is shifting to the top of the heart, which leads to suction of blood from large veins into the atrium. At the same time, atrium at this moment in a relaxed state is stretched. This effect is more pronounced while reducing the right ventricle.
The unidirectional current of blood from the atria in the ventricles contributes to the structure of the valves. During the atrial systole, the pressure in them becomes higher than the pressure in the ventricles, therefore the slad valves are open in the right and left atrial and ventricular holes. At this time, the ventricles are in a state of diastole, and the pressure in them is less than in the pressure in the aorta and the pulmonary artery. This leads to the closure of semi-lunut valves.
Next begins diastole atrial and stomach systoles. The pressure in the ventricles becomes greater than the pressure in the atrialists, in the aorta and the pulmonary artery. In this regard, the slad valves are closed, preventing the reverse current of blood from the ventricles in the atrium, and the semi-lunut valves open, contributing to throwing blood. Valve damage may result in the fact that they will not be able to fully open (and stenosis occurs), or it is tightly closed (and there is deficiency of treasures). As a result, myocardia is forced to develop greater strength and throw out a larger blood volume, which leads to myocardial hypertrophy and / or to expand the cavities of the heart - dilatation.
The left and right ventricles for each reduction are pushed respectively in the aorta and pulmonary trunk of about 60 - 80 ml of blood. The volume is the same for the left and right ventricles, if the body is at rest. This volume is called systolic or shock. Multiplying the systolic volume by the number of reductions in 1 minute, you can calculate a minute volume. It averages 4.5 - 5 liters.
Systolic and minute heart volumes are not constant. Their value, as well as heart rate (heart rate) depends on the age-related genital and individual characteristics of the person. For example, at a physically trained person in peace systolic and minute volumes more than the untouched, and the heart rate is less. CSS athletes are often within 50 - 60 ice / min. With the hard work of the heart, the parameters of its functioning change dramatically. A minute volume can reach 20-30 liters in an adult. In untranslated people, this increase in volume occurs mainly due to heart rate (which is very uneconomical), in trained - mainly as a result of an increase in the systolic volume of the heart.
In the vessels, the blood moves due to the pressure gradient in the direction from high to the low. The ventricle is the body that creates the specified gradient.
Changing the reduction states (systole) and relaxation (diastoles) of the heap departments, which is repeated cyclically, is called a cardiac cycle. At frequency (heart rate) 75 in 1 min, the duration of the entire cycle is 0.8 s.
The heart cycle is conveniently viewed, starting with the total atrial diastole and ventricles (heart pause). In this case, the heart is in such a state: the crescent valves are closed, and atrioventricular open. Blood from the veins comes out freely and completely fills the cavities of atrial and ventricles. The blood pressure in them, as in the veins lying nearby, is about 0 mm Hg. Art. In the right and left half of the heart of an adult, at the end of the general diastole, it is placed at about 180-200 mji blood.
Systole atrial. The excitation, originated in the sinus node, first forth in the myocardium atrial, is atrial systole (0.1 s). At the same time, due to the reduction of muscle fibers located around the vein holes, it overlaps their lumen. A peculiar closed atrioventricular cavity is formed. When the myocardial is reduced, the pressure in them increases to 3-8 mm Hg. Art. (0.4-1.1 kPa). As a consequence, some of the blood from the atria through the open atrioventricular holes turns into the ventricles, bringing the volume of blood in them to 130-140 ml (finite-diastolic volume of ventricles - KDO). After that, the diastole atrial (0.7 s) begins.
Systole ventricles. Currently, the leading excitation system is applied to ventricular cardiomyocytes and stomach systole begins, which lasts about 0.33 s. It is divided into two periods. Each periods respectively consists of phases.
The first voltage period continues until the crescent valves open. To open their pressure in the ventricles should rise to higher Levelthan in the respective arterial trunks. The diastolic pressure in the aorta is about 70-80 mm Hg. Art. (9.3-10.6 kPa), and in the pulmonary artery-10-15 mm Hg. Art. (1.3-2.0 kPa). The voltage period lasts about 0.08 s.
It begins with the asynchronous reduction phase (0.05 seconds), as evidenced by the unlimited reduction of all the fibers of the ventricles. The first cardiomyocytes that are located near the fiber conductive system are reduced.
The next phase of isometric reduction (0.03 C) is characterized by involving in the process of reducing all ventricular fibers. The beginning of the reduction of ventricles leads to the fact that with closed-even crescent valves, the blood rushes to the site of no pressure - towards the atrium. Atrioventricular valves lying on its path, blood current is closed. Incending them in atrium prevent tendon threads, and papillary muscles, shrinking, make them even more stable. As a result, closed cavities of the ventricles are created for a while. And so far, due to the reduction in the ventricles, blood pressure is not raised above the level required to open the crescent valves, no significant fiber reduction occurs. Only their internal stress increases. Thus, in the phase of isometric reduction, all the heart valves are closed.
The period of expulsion of blood begins with the opening of the aorta valves and the pulmonary artery. It lasts 0.25 ° C and consists of a phase of fast (0.12 seconds) and slow (0.13 (c) blood expulsion. Aortic valves Opened at blood pressure of about 80mirt. Art. (10.6 kPa), and pulmonary - 15 mm Hg. in (2.0 kPa). The relatively narrow holes of the arteries can immediately skip the entire volume of blood pushing (70 ml), therefore the reduction in myocardium leads to a further increase in blood pressure in the ventricles. In the left, it increases to 120-130 mm Hg. Art. (16.0-17.3 kPa), and in the right-to 20-25 mm RT. Art. (2.6-3.3 kPa). The high pressure gradient created between the ventricle and the aorta (pulmonary artery) contributes to the rapid ejection of the part of the blood into the vessel.
However, due to a relatively small throughput The vessel in which there was still blood overwhelmed. Now the pressure is growing already in vessels. The pressure gradient between ventricles and vessels gradually decreases, and the blood flow rate slows down.
Due to the fact that diastolic pressure In the pulmonary artery below, the discovery of the exile valves from the right ventricle begins somewhat earlier than with the left. And through a low gradient, the expulsion of blood ends later. Therefore, the diastolic right ventricle goes to 10-30 ms longer than the left.
Diastole. At the end, when the pressure in the vessels increases to the level of pressure in the cavities of the ventricles, the height of the blood stops. Their diastole begins, which lasts about 0.47 s. The end time of the systolic expulsion of blood coincides with the time of stopping the reduction of ventricles. Usually 60-70 ml of blood remains in the ventricles (of course-systolic volume - CSR). The cessation of expulsion leads to the fact that the blood that is contained in the vessels, the reverse current closes the crescent valves. This period is called protodiastolic (0.04 seconds). After that, the voltage is falling, and is the isometric period of relaxation (0.08 (C), after which the ventricles under the influence of blood entering begin to straighten.
At present, the atrium after systole is already completely filled with blood. Atrial diastole lasts about 0.7 s. Atrium is filled mainly by blood, passively follows from the veins. But you can select and "active" component, which is manifested in connection with the partial coincidence of its diastole from systolic ventricles. When reducing the latter, the plane of the atrioventricular partition is shifted in the direction of the heart of the heart; As a result, the successive effect is formed.
When the stress of the ventricular wall falls, the atrioventricular valves of blood flow open. Blood filling the ventricle, gradually spreads them.
The period of filling the ventricles with blood is divided into the phases of the rapid (with atrial diastole) and slow (under systolic atrial) filling. Before the start of the new cycle (atrial systole), the ventricles, like atrium, manage to fully fill in blood. Therefore, due to blood flow during the atrial systole, the intragastric volume increases about only 20-30%. But this indicator significantly increases with the intensification of the work of the heart when the total diastole is reduced and blood does not have time to fill the ventricles.
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