home Polyps Sympathetic and parasympathetic innervation of the heart. Innervation of the heart. Clinical anatomy of the heart. Monitoring the pumping function of the heart

Sympathetic and parasympathetic innervation of the heart. Innervation of the heart. Clinical anatomy of the heart. Monitoring the pumping function of the heart

Heart nerves

The heart receives sensitive, sympathetic and parasympathetic innervation. The sympathetic fibers that run as part of the heart nerves from the right and left sympathetic trunks carry impulses that accelerate the heart rate and expand the lumen of the coronary arteries, and parasympathetic fibers (a component of the cardiac branches of the vagus nerves) conduct impulses that slow down the heart rate and narrow the lumen of the coronary arteries ... Sensory fibers from the receptors of the walls of the heart and its vessels go as part of the heart nerves and cardiac branches to the corresponding centers of the spinal cord and brain.

The scheme of innervation of the heart (according to V.P. Vorobyov) can be represented as follows: sources of innervation of the heart are the heart nerves and branches, following to the heart; extraorganic cardiac plexuses (superficial and deep), located near the arch of the aorta and the pulmonary trunk; intraorgan cardiac plexus, which is located in the walls of the heart and is distributed in all their layers.

Cardiac nerves(upper, middle and lower cervical, as well. thoracic) start from the cervical and upper thoracic (II-V) nodes of the right and left sympathetic trunks (see "Autonomic nervous system"). Cardiac branches originate from the right and left vagus nerves (see "Vagus nerve").

Superficial extraorganic cardiac plexuslies on the anterior surface of the pulmonary trunk and on the concave semicircle of the aortic arch; deep extraorgan cardiac plexuslocated behind the aortic arch (in front of the tracheal bifurcation). The upper left cervical heart nerve (from the left upper cervical sympathetic node) and the upper left cardiac branch (from the left vagus nerve) enter the superficial extraorgan cardiac plexus. All the other cardiac nerves and cardiac branches named above enter into the deep extraorganic cardiac plexus.

The branches of the extraorganic cardiac plexuses pass into a single intraorgan cardiac plexus.Depending on which of the layers of the heart wall it is located in, this single intraorgan cardiac plexus is conditionally subdivided into closely related subepicardial, intramuscular and subendocardial plexus.The intraorganic cardiac plexus contains nerve cells andtheir clusters, forming small-sized nerve heart nodules, ganglia cardiaca. There are especially many nerve cells in the subepicardial heart plexus. According to V.P. Vorobiev, the nerves that make up the subepicardial cardiac plexus have a regular localization (in the form of nodal fields) and innervate certain parts of the heart. Accordingly, there are six subepicardial cardiac plexuses: 1) right frontand 2) left front.They are located in the thickness of the anterior and lateral walls of the right and left ventricles on both sides of the arterial cone; 3) anterior atrial plexus- in the anterior wall of the atria; 4) right posterior plexusdescends from the posterior wall of the right atrium to the posterior wall of the right ventricle (fibers go from it to the sinus-atrial node of the cardiac conduction system); five) left posterior plexusfrom the lateral wall of the left atrium continues down to the posterior wall of the left ventricle; 6) posterior plexus of the left atrium(Haller's sinus plexus) is located in the upper part of the posterior wall of the left atrium (between the orifices of the pulmonary veins).

The innervation of the heart is the supply of nerves to it, which ensures the connection of this organ with the central nervous system. It sounds simple, but everyone knows how amazing the human body is. Nerve supply to the heart is a real separate bioworld. And also a complex but interesting anatomical topic. And now I would like to pay a little attention to its consideration.

Parasympathetic innervation

It is worth talking about it first of all, since the heart receives not one, but several innervations - parasympathetic, sympathetic and sensitive. You should start with the first of these.

So, preganglionic nerve fibers (which are characterized by slow conduction of impulses) belong to the vagus nerves. They end in the intramural ganglia of the heart - nodes, which are a collection of special cells consisting of axons, dendrites and bodies.

In the ganglia are the second neurons with processes that go to the conducting system, coronary vessels and the myocardium - the middle layer of the heart, which makes up the main part of it. Also there are H-cholinergic receptors. These are fast-acting ionotropic receptors - membrane channels through which ions move.

On effector cells (those that destroy antibodies), in turn, M-cholinergic receptors are located, transmitting a signal through heterotrimeric G-proteins.

It is important to note that when the central nervous system is excited, various biologically active substances, peptides (amino acid chains), enter the synaptic cleft (the gap between the membrane of the axon and the body / dendrite). This is important to take into account, since they are characterized by a modulating function that allows you to change the magnitude and direction of the heart's reaction to the main mediator (a substance that transmits impulses from one cell to another).

It should also be mentioned that fibers from the right vagus nerve supply the sinus-atrial node (sinoatrial), as well as the myocardium of the right atrium. And from the left - atrioventricular.

Processes in progress

Continuing the theme of the parasympathetic innervation of the heart, we should talk about some important processes. It is important to know that the right vagus nerve affects heart rate, and the left one affects AV conduction. The innervation of the ventricles, by the way, is very weakly expressed, therefore, it has an indirect effect - only by inhibiting sympathetic effects.

All this was first studied in the middle of the 19th century by the Weber brothers. It was they who revealed that irritation of the vagus nerves (which all of the above applies to) inhibits the work of the main organ - up to a complete stop.

However, it is worth returning to the M-cholinergic receptors. They are influenced by acetylcholine, which is a mediator responsible for neuromuscular transmission. In this case, it activates the K + channels. They are pores filled with water and act as a catalyst for the transport of K + ions.

As a result of this complex process, in simple terms, the following can happen:

Exit K + from the cell. Consequences: a slowdown in the rhythm and conduction in the AV node, a decrease in excitability and strength of contractions, a decrease in the refractory period.
Decreased activity of protein kinase A, which is responsible for the activation and inactivation of enzymes in the body. As a consequence, a decrease in its conductivity.

By the way, it is also worth noting attention to such a concept as "the escape of the heart." This is a phenomenon in which its contractions stop due to the fact that the vagus nerve has been in an excited state for too long, but then immediately recover. A unique phenomenon ... In fact, this is how the body avoids the mortal danger - cardiac arrest.

Sympathetic innervation

It is also important to touch it with attention. Based on the foregoing, one can understand that it is difficult to describe the innervation of the heart briefly, especially in simple language. But it's easier to deal with the sympathetic. At least because her nerves, unlike the vagus ones, are evenly distributed throughout all parts of the heart.

So, there are the first neurons - pseudo-unipolar cells. They are located in the lateral horns of the upper 5 segments of the thoracic spinal cord. Their processes end in the upper and cervical nodes, where the second neurons begin, extending directly to the heart (as discussed above).

How sympathetic nerves affect the heart was studied in the 19th century by the Zion brothers, and then by Ivan Petrovich Pavlov. They found that as a result of this, there is a positive chronotropic effect. That is, an increase in the frequency of contractions.

Sensitive innervation

It can be both conscious and reflex. The first type of sensitive innervation of the heart is carried out:

The neurons of the spinal nodes (the first). Their receptor endings are formed by dendrites in the layers of the heart wall.
The second neurons of the sympathetic nervous system. They are located in the own nuclei of the posterior horns of the spinal cord.
Third neurons. Located in the ventrolateral nuclei. Their dendrites extend to the cells of the fourth and second layers of the postcentral gyrus.

What about reflex innervation? It is provided by the neurons of the lower and upper nodes of the vagus nerve, about which so much has been described above.

There is one more nuance that should be noted with attention. Sensitive innervation of the heart (this is usually not shown in the diagram) is carried out by the afferent cells of the second type of Dogel, which are located in the nodes of the cardiac plexus. It is thanks to their dendrites that receptors are formed in the heart wall, with which the axons that close on the effector neurons form an eccentral reflex arc. It is another complex system that provides instant regulation of blood supply to all local parts of the human heart.

Myocardium

This is the middle muscle layer of the heart. It makes up the bulk of its mass, as mentioned above. And since we are talking about the activity of the heart, then the myocardium cannot be ignored.

Its feature is the creation of rhythmic muscle movements (alternating contractions with relaxation). But in general, the myocardium has four properties - excitability, automatism, conductivity, and contractility. Each of them is briefly worth talking about.

Excitability. In fact, this is the "response" of the heart to a stimulus (chemical, mechanical, electrical). It is interesting that the muscle reacts only to strong influences. The stimulus of the subthreshold force is not perceived by it. This is all due to the special structure of the myocardium - excitement sweeps through it quickly. Therefore, for the muscle to respond, it must be pronounced.
Automatism and conductivity. This is the name of the ability of pacemaker cells (pacemakers) to initiate spontaneous excitation, which does not require the participation of neurohumoral control. It arises in the conducting system, after which it spreads to all parts of the myocardium.
Contractility. This property is the easiest to understand. And there are some peculiarities here. Few people know that the strength of the contractions depends on the length of the muscle fibers. The more blood flows to the heart, the more they stretch. And the more powerful the contractions become. This is important, since the strength depends on the complete emptying of the cardiac cavities, which, in turn, maintains the balance of the amount of flowing and flowing blood.

Muscle structure and blood flow

A lot has been said above about the sensitive, sympathetic and parasympathetic innervation of the heart. Now you can move on to the topic of his blood supply. Which is also very detailed, interesting and complex.

The heart muscle is the center of the blood circulation. It is her work that ensures the movement of the most important biological fluid through the vessels.

Everyone knows approximately how the heart works. This is a muscular organ located in the middle of the chest. It is divided into left and right compartments, each with a ventricle and an atrium. This is where it all begins. The blood that enters the organ first enters the atrium, then into the ventricle, and then into the large arteries. The direction in which the biofluid moves is set by the valves.

Interestingly, low-oxygen blood travels from the heart to the lungs. There it is purified from CO 2, followed by oxygenation. Then the blood enters the venules, and then into the larger veins. Then it goes back to the heart. Once in the vena cava, blood enters the right atrium.

This is how you can describe the systemic circulation in simple terms. Paying attention to the diagram shown below, you can roughly imagine how everything looks like. And, naturally, the blood supply to the heart also occurs according to the described principle.

Blood pressure

A little worth talking about him. After all, pressure is directly related to the blood supply to the heart. It is created every time the next "portion" is thrown into the aorta and into the pulmonary artery. And it happens all the time.

The pressure becomes higher when the heart, making stronger and more frequent contractions, pumps blood into the aorta. And also with narrowing of arterioles. Pressure drops when the arteries expand. However, its value is also influenced by the amount of circulating blood, as well as how viscous it is.

An interesting nuance should be noted. The blood pressure gradually decreases with distance from the muscle. The minimum indicators are observed in the veins. And the difference between high pressure (aorta) and low (pulmonary, vena cava) is a factor that ensures continuous blood flow.

What about the indicators? Normal pressure is 120 to 70 (allowable 80) mm Hg. Art. It is stable up to about 40 years. Then, the older a person gets, the higher his pressure. For people aged 50 to 60, the norm is 144/85 mm Hg. Art. And for those over 80 - 150/80 mm Hg. Art.

Abnormalities have their own names, and most are familiar with them. Hypertension is a persistent increase in blood pressure seen in a person who is at rest. And hypotension is called lowering. Whatever of the two a person suffers, his blood supply to his organs will be disrupted to some extent.

Heart rate

Enough has been said about the innervation of the heart, intracardiac and extracardiac nerve plexuses - now it's worth talking about heart rate. Many people think that heart rate is just synonymous with pulse. Well, wrong.

This is the number of contractions performed by the heart muscle in a certain time unit. Usually in a minute. And the pulse is the number of artery dilations that occur when the heart ejects blood. Its value may coincide with the heart rate, but only in completely healthy people.

If, for example, the rhythms of the heart are violated, then the muscle contracts irregularly. It happens that two times in a row - then the left ventricle simply does not have time to fill with blood. In this case, the second contraction occurs when it is empty. This means that blood is not ejected from it into the aorta. Accordingly, the pulse in the arteries is not audible. But the reduction has occurred, which means that the heart rate is "counting".

At the same time, there is such a thing as a pulse deficit. Observed with atrial fibrillation. It is characterized by a discrepancy between the heart rate and the pulse rate. The frequency of contractions in such cases cannot be detected by measuring the pulse. To do this, you need to listen to the beats of the heart. With a phonendoscope, for example.

Heart rate norms

Every person who is not indifferent to his body should know them. Well, here is a generally accepted table of age norms for heart rate in healthy people.

Human age	Contraction frequency (minimum and maximum)	Mean

Up to 1 month
From 1 month to 1 year
1 to 2 years
4 to 6
6 to 8
8 to 10
10 to 12
12 to 15
Adults under 50

It should be noted that if a person has an increased frequency of contractions, then this is tachycardia. One has to worry when their number exceeds 80 per minute. If the frequency of contractions is less than 60, then there is also nothing good in this, since this phenomenon is a violation - bradycardia.

According to the table of heart rate norms by age, you can compare your indicators. But it is also worth remembering that the frequency depends on the fitness of the person, his gender and body size. In patients with good physical fitness, the heart rate is always below normal - about 50 per minute. In women, as a rule, it is 5-6 higher per unit of time than in men.

By the way, heart rate also depends on daily biorhythms, this should be taken into account. The highest rates are from 15:00 to 20:00.

Slight fluctuations in heart rate and heart rate are normal, but if they are observed too often, then there is cause for concern. This is often a symptom of vegetative-vascular dystonia, endocrine disorders and other diseases.

Heart volume

Another topic that should be noted with attention. There are such concepts - systolic and cardiac output. They are directly related to the innervation of the heart and its blood supply. And about this - a little more.

The amount of blood that the ventricle ejects in a certain unit of time (generally accepted - a minute) is called the minute volume of the heart. In a healthy adult, it is approximately 4.5-5 liters. By the way, the volume is the same for both the left and right ventricles.

If you divide the minute volume by the number of muscle contractions, you get the notorious systolic. The calculation is extremely simple. The heart of a healthy person performs approximately 70-75 contractions per minute. This means that the systolic volume is 65-70 milliliters of blood.

Although, of course, these are generalized indicators. Moving away from the topic of physiology and innervation of the heart, it is worth noting the so-called integral rheography method. This is a way by which you can very accurately determine the notorious volumes of a particular person. Naturally, it is not simple - the electrical resistance of tissues, blood resistance and many other data are recorded. There are also formulas for more complex calculations. But this is already a complex anatomy, and this topic does not directly concern the innervation of the heart.

Conclusion

So, above, the autonomic innervation of the heart, the structure of the muscle, the topic of blood supply, pressure and heart rate were considered in some detail, albeit briefly. Based on all of the above, we can draw a conclusion, which is already obvious: everything in our body is interconnected. One cannot exist without the other. Especially when it comes to the heart. After all, his work is the main source of mechanical energy for the movement of blood in the vessels, ensuring the continuity of metabolism and maintaining energy in the body.

This muscle is functional, and it has a well-developed multistage system of regulation, due to which its activity is adapted to the dynamically changing conditions of the functioning of the circulatory system, as well as to the needs of the body.

To consolidate knowledge concerning the topic under discussion, you should pay attention to the schemes presented above.

Heart is abundant innervated organ... Among the sensitive formations of the heart, two populations of mechanoreceptors are of primary importance, concentrated mainly in the atria and the left ventricle: A-receptors respond to changes in the tension of the heart wall, and B-receptors are excited during its passive stretching. Afferent fibers associated with these receptors are part of the vagus nerves. Free sensory nerve endings, located directly under the endocardium, are the terminals of afferent fibers passing through the sympathetic nerves.

Efferent innervation of the heart carried out with the participation of both divisions of the autonomic nervous system. The bodies of sympathetic preganglionic neurons involved in the innervation of the heart are located in the gray matter of the lateral horns of the three upper thoracic segments of the spinal cord. Preganglionic fibers are directed to the neurons of the superior thoracic (stellate) sympathetic ganglion. The postganglionic fibers of these neurons, together with the parasympathetic fibers of the vagus nerve, form the upper, middle and lower cardiac nerves. Sympathetic fibers penetrate the entire organ and innervate not only the myocardium, but also the elements of the conducting system.

The bodies of parasympathetic preganglionic neurons involved in innervation of the heart... are located in the medulla oblongata. Their axons are part of the vagus nerves. After the vagus nerve enters the chest cavity, branches depart from it, which are included in the heart nerves.

The processes of the vagus nerve, which are part of the heart nerves, are parasympathetic preganglionic fibers... From them, excitation is transmitted to intramural neurons and then - mainly to the elements of the conducting system. The influences mediated by the right vagus nerve are mainly addressed to the cells of the sinoatrial, and the left - to the cells of the atrioventricular node. The vagus nerves do not have a direct effect on the ventricles of the heart.

Innervating the fabric of pacemakers... autonomic nerves are able to change their excitability, thereby causing changes in the frequency of generation of action potentials and heart contractions ( chronotropic effect). Nervous influences change the rate of electrotonic transmission of excitation and, consequently, the duration of the phases of the cardiac cycle. Such effects are called dromotropic.

Since the action of mediators of the autonomic nervous system is to change the level of cyclic nucleotides and energy metabolism, autonomic nerves in general are able to influence the strength of heart contractions ( inotropic effect). Under laboratory conditions, the effect of changing the value of the excitation threshold of cardiomyocytes under the action of neurotransmitters was obtained; it is designated as batmotropic.

The listed pathways of the nervous system on the contractile activity of the myocardium and the pumping function of the heart are, although extremely important, but secondary to myogenic mechanisms, modulating influences.

Innervation of the heart and blood vessels

The activity of the heart is regulated by two pairs of nerves: vagus and sympathetic (Fig. 32). The vagus nerves originate in the medulla oblongata, and the sympathetic nerves branch off from the cervical sympathetic node. The vagus nerves inhibit cardiac activity. If you start to irritate the vagus nerve with an electric current, then there is a slowdown and even arrest of heart contractions (Fig. 33). After the termination of irritation of the vagus nerve, the work of the heart is restored.

Figure: 32. Scheme of innervation of the heart

Figure: 33. Influence of irritation of the vagus nerve on the heart of the frog

Figure: 34. Effect of irritation of the sympathetic nerve on the frog heart

Under the influence of impulses coming to the heart through the sympathetic nerves, the rhythm of cardiac activity increases and each heartbeat intensifies (Fig. 34). In this case, the systolic, or stroke, blood volume increases.

If the dog is in a calm state, his heart beats 50 to 90 times in 1 minute. If you cut all the nerve fibers heading to the heart, the heart now contracts 120-140 times per minute. If only the vagus nerves of the heart are cut, the heart rate will increase to 200-250 beats per minute. This is due to the influence of the preserved sympathetic nerves. The heart of man and many animals is under the constant restraining influence of the vagus nerves.

The vagus and sympathetic nerves of the heart usually act in concert: if the excitability of the center of the vagus nerve increases, then the excitability of the center of the sympathetic nerve decreases accordingly.

During sleep, in a state of physical rest of the body, the heart slows down its rhythm due to an increase in the influence of the vagus nerve and some decrease: the influence of the sympathetic nerve. During physical work, the heart rate increases. In this case, there is an increase in the influence of the sympathetic nerve and a decrease in the influence of the vagus nerve on the heart. In this way, an economical mode of operation of the heart muscle is ensured.

The change in the lumen of blood vessels occurs under the influence of impulses transmitted to the walls of the vessels along vasoconstrictor nerves. The impulses coming along these nerves arise in the medulla oblongata in vasomotor center... The opening and description of the activities of this center belongs to F.V. Ovsyannikov.

Ovsyannikov Philip Vasilievich (1827-1906) - an outstanding Russian physiologist and histologist, full member of the Russian Academy of Sciences, teacher I.P. Pavlova. FV Ovsyannikov studied the issues of blood circulation regulation. In 1871 he discovered the vasomotor center in the medulla oblongata. Ovsyannikov studied the mechanisms of respiration regulation, the properties of nerve cells, and contributed to the development of the reflex theory in domestic medicine.

Reflex influences on the activity of the heart and blood vessels

The rhythm and strength of the heartbeats change depending on the emotional state of the person, the work he does. The human condition also affects the blood vessels, changing their lumen. You often see how with fear, anger, physical stress, a person either turns pale or, on the contrary, blushes.

The work of the heart and the lumen of the blood vessels are associated with the needs of the body, its organs and tissues in providing them with oxygen and nutrients. The adaptation of the activity of the cardiovascular system to the conditions in which the body is located is carried out by nervous and humoral regulatory mechanisms, which usually function in an interconnected manner. Nerve influences that regulate the activity of the heart and blood vessels are transmitted to them from the central nervous system along the centrifugal nerves. By irritation of any sensitive endings, you can reflexively cause a decrease or increase in heart rate. Heat, cold, an injection and other irritations cause excitement at the endings of the centripetal nerves, which is transmitted to the central nervous system and from there, along the vagus or sympathetic nerve, reaches the heart.

Test 15

Immobilize the frog so that it retains the medulla oblongata. Do not destroy the spinal cord! Pin the frog to the board, belly up. Bare your heart. Count the number of heartbeats in 1 min. Then use tweezers or scissors to hit the frog's abdomen. Count the number of heartbeats in 1 min. The activity of the heart after a blow to the abdomen slows down or even temporarily stops. This happens reflexively. A blow to the abdomen causes excitation in the centripetal nerves, which reaches the center of the vagus nerves through the spinal cord. Hence, excitation along the centrifugal fibers of the vagus nerve reaches the heart and inhibits or stops its contraction.

Explain why the frog's spinal cord cannot be destroyed in this experiment.

Is it possible to cause cardiac arrest of a frog when it strikes its abdomen if the medulla oblongata is removed?

The centrifugal nerves of the heart receive impulses not only from the medulla oblongata and spinal cord, but also from the overlying parts of the central nervous system, including from the cerebral cortex. Pain is known to cause the heart to beat faster. If a child was given injections during treatment, then only the appearance of a white coat will cause an increase in heart rate. This is evidenced by the change in cardiac activity in athletes before the start, in pupils and students - before exams.

Fig. 35. The structure of the adrenal glands: 1 - the outer, or cortical, layer in which hydrocortisone, corticosterone, aldosterone and other hormones are produced; 2 - the inner layer, or medulla, in which adrenaline and norepinephrine are formed

Impulses from the central nervous system are transmitted simultaneously along nerves to the heart and from the vasomotor center along other nerves to the blood vessels. Therefore, usually the heart and blood vessels reflexively respond to irritation from the external or internal environment of the body.

Humoral regulation of blood circulation

The activity of the heart and blood vessels is influenced by chemicals in the blood. So, in the endocrine glands - the adrenal glands - a hormone is produced adrenalin (fig. 35). It speeds up and enhances the activity of the heart and narrows the lumen of the blood vessels.

In the nerve endings of the parasympathetic nerves is formed, acetylcholine... which expands the lumen of blood vessels and slows down and weakens cardiac activity. Some salts also affect the work of the heart. An increase in the concentration of potassium ions inhibits the work of the heart, and an increase in the concentration of calcium ions causes an increase in the activity of the heart.

Humoral influences are closely related to the nervous regulation of the circulatory system. The release of chemicals into the bloodstream and the maintenance of certain concentrations in the blood are regulated by the nervous system.

The activity of the entire circulatory system is aimed at providing the body in different conditions with the necessary amount of oxygen and nutrients, removing metabolic products from cells and organs, and maintaining a constant level of blood pressure. This creates conditions for maintaining the constancy of the internal environment of the body.

Innervation of the heart

The sympathetic innervation of the heart is carried out from the centers located in the lateral horns of the three upper thoracic segments of the spinal cord. The preganglionic nerve fibers emanating from these centers go to the cervical sympathetic ganglia and transmit excitation there to neurons, the postganglionic fibers from which innervate all parts of the heart. These fibers transmit their effect on the structures of the heart through the mediator of norepinephrine and through the p-adrenergic receptors. Pi receptors predominate on the membranes of the contractile myocardium and the conducting system. There are about 4 times more of them than P2 receptors.

The sympathetic centers that regulate the work of the heart, in contrast to the parasympathetic ones, do not have a pronounced tone. An increase in impulses from the sympathetic nerve centers to the heart occurs periodically. For example, when these centers are activated, caused by reflex or downward influences from the centers of the trunk, hypothalamus, limbic system and cerebral cortex.

Reflex influences on the work of the heart are carried out from many reflexogenic zones, including from the receptors of the heart itself. In particular, an increase in myocardial tension and an increase in atrial pressure are an adequate stimulus for the so-called A-receptors of the atria. In the atria and ventricles there are B-receptors that are activated when the myocardium is stretched. There are also pain receptors that initiate severe pain when there is insufficient oxygen delivery to the myocardium (heart attack pain). Impulses from these receptors are transmitted to the nervous system along fibers passing in the vagus and branches of the sympathetic nerves.

The innervation of the heart and its physiological characteristics are information, without which it will be difficult to clearly imagine all the facets of the work of this important organ in the human body. It is interesting enough to know about how the brain communicates with the center of the circulatory system in our body. In addition, the structure and principles of cardiac functioning are also noteworthy.

Heart work

The key, one might even say, the central organ of the circulatory system of the human body is the heart. It is hollow, cone-shaped and located in the chest cavity. If we describe its function using extremely simple images, then we can say that the heart works like a pump, due to which the blood flow necessary for the full functioning of the body is preserved in the complex system of arteries, vessels and veins.

An interesting fact is that the heart is capable of producing its own electrical activity. Determined by such quality as automation. This feature allows even an isolated cell of the heart muscle to contract by itself. This quality is extremely important for the stable operation of this body.

Features of the structure

Initially, the diagram of the heart makes you pay attention to where this organ is located. It is located, as written above, in the chest cavity, and so that the smaller part of it is localized on the right, and the larger, respectively, on the left. So it is wrong to think that the whole heart is in the left side of the chest.

But more precisely, the place where the heart is located is the mediastinum, in which there are two so-called floors - lower and upper.

The size of the heart is on average equal to the volume of the hand, which is clenched into a fist. It is worth knowing that the heart is divided by a special partition into two halves - left and right. In turn, each of these parts has such sections as the ventricle and atrium, between which there is an opening. It closes by means The peculiarity of this valve is its structure: on its right side, it has three leaves, and on the left - two.

Right ventricle

In this case, we are talking about a cavity, on the inner side of which there are many muscle bars. The papillary muscles are also located here. It is from them that the tendon filaments extend to the valve that closes the opening between the right ventricle and the right atrium.

As for the valve mentioned, its structure includes three leaflets built from the endocardium. Once the right ventricle contracts, this valve closes the opening, eventually blocking the return flow of blood. By the way, it is from this part of the heart that goes to the respiratory system. Venous blood moves along it.

Left ventricle

If we compare it with the right one, then it should be noted that in this case the wall is noticeably thicker. Paying attention to the inner surface of its wall, you can see the muscle bars and papillary muscles. It is from them that the tendon threads depart, which are fixed at the edges of the left atrioventricular valve.

The heart is also where the largest arterial trunk, called the aorta, emerges. It is above the valve of this trunk that the holes are located, leading to the coronary arteries that feed the heart.

It is important to know that all arterial blood enters the left atrium and from there it enters the left ventricle, which was discussed above. As you can see, all the elements of the heart are closely related and if one of them malfunctions, this will affect the entire organ.

Vessels

Speaking of the vessels through which the blood supply to the heart is carried out, it is worth noting that they pass along the outside of the organ in special grooves. Moreover, there are those that enter the heart, and those that come out of it.

There are also longitudinal interventricular grooves on the inferior and anterior ventricular surfaces. There are two such grooves in total - the posterior and the anterior, but both of them are directed to the apex of the organ.

Do not forget about the coronal groove, which is located between the lower and upper chambers. The right and left coronary arteries of the heart, or rather, their branches, are located in it. Their mission is to nourish this organ with blood. That is why, if a cholesterol plaque forms in this area or a blood clot gets there, a person's life is at risk.

At the same time, there are also other large arteries of the heart, as well as the venous trunks that exit from this organ.

Valves

These elements are attached to the so-called skeleton of the heart, which consists of two fibrous rings. Those, in turn, are located between the upper and lower chambers.

There are only 4 valves in the human heart.

The first (conventionally) is called the right atrioventricular, or tricuspid. Its main function is to block the possibility of reverse blood flow from the right ventricle.

The next, left valve, has only two leaves, which is why it got the corresponding name - bivalve. It can also be called the mitral valve. It is required to form a flap that prevents blood from flowing from the left atrium to the left ventricle of the heart.

The third valve - without it, the opening of the pulmonary column would remain open. This would cause blood to flow back into the ventricle.

The heart diagram also includes a fourth valve, which is located where the aortic outlet is located. It prevents blood flow from flowing back to the heart.

What you need to know about the conduction system

The blood supply to the heart is not the only function on which the stable functioning of this organ depends. The formation of the heartbeat is also extremely important. It is thanks to the conducting system that a contraction of the muscle layer is created, which serves as the beginning of the work of the main organ of the circulatory system.

At the same time, it is important to note the fact that the sinus-atrial node is the place where the impulse is generated, giving the command to contract the heart muscle. As for its location, it is located where the vena cava passes into the right atrium.

The structures described above have such an effect on the heart, thanks to which the following processes become possible:

Coordination of ventricular and atrial contractions;

Rhythmic pulse generation;

Synchronous involvement of all cells of the muscle layer of the ventricles in the contractile process (without this, increasing the efficiency of contractions would be an extremely difficult task).

Innervation of the heart

Initially, it is worth understanding what this terminology implies. So, innervation is nothing more than the saturation of a specific part of the body with nerves for a stable and full-fledged connection with the central nervous system. In other words, it is the neural network through which the brain controls muscles and organs. A similar feature of the body cannot be ignored by studying such a topic as the structure and work of the heart.

A more detailed study of this topic can begin with the following fact: the process of contraction of the heart muscle is controlled by both the endocrine and nervous systems. In this case, the changes in the rhythm of contractions are most directly influenced by the autonomic innervation of the heart. These are sympathetic and parasympathetic stimulation. The first increases the frequency of contractions, the second, accordingly, decreases it.

The general activity of this organ is controlled by the heart centers and the medulla oblongata. From these centers, with the help of sympathetic and parasympathetic nerve fibers, impulses are transmitted that affect the strength of contractions, their frequency and the speed of trioventricular conduction. As for the scheme of transmission of nerve influences on the heart, here this role, as in any other organs, is played by mediators. In the sympathetic system, this is norepinephrine, and acetylcholine in the parasympathetic, respectively.

Characteristic features of cardiac innervation

The intraorgan nervous apparatus of the heart is rather complicated. It is represented by nerves that start their way from the thoracic aortic plexus and only then enter the main organ of the circulatory system, as well as the ganglia. The latter are nothing more than an accumulation of cells located in the center of the above apparatus. Nerve fibers are also part of this system. They take their origin from the cardiac ganglia. Effectors and receptors make this structure complete.

The innervation of the heart also implies the presence of sensory fibers. They consist of the spinal nodes and the vagus nerve. This group also includes autonomic motor fibers.

Sympathetic fibers

So, if you pay attention to such a facet of the topic under consideration as the sympathetic innervation of the heart, then initially you should pay attention to the source of these fibers. In other words, determine where they come from to the central organ of the circulatory system. The answer is quite simple: the lateral horns of the upper thoracic segments of the spinal cord.

The essence of the effect of sympathetic stimulation is reduced to the effect on the force of contraction of the ventricles and atria, which is expressed in its increase. In fact, we are talking about the positive. But that's not all - the heart rate increases. In this case, it makes sense to talk about a positive chronotropic effect. And the last effect of sympathetic innervation, which is worth paying attention to, is a dromotropic effect, namely, the effect on the interval between contractions of the ventricles and atria.

Parasympathetic part of the system

The innervation of the heart also includes these processes. This type of fiber comes to the heart as part of the vagus nerve, and from both sides.

If we talk about the "right" fibers, then their function is reduced to the innervation, respectively, of the right atrium. In the area of \u200b\u200bthe sinus-atrial node, they form a dense plexus. As for the left vagus nerve, the fibers that come with it come to the atrioventricular node.

Speaking about the effect that the parasympathetic innervation of the heart produces, it is worth mentioning a decrease in the force of atrial contraction and a decrease in heart rate. But the atrioventricular delay increases. It is easy to conclude that the work of nerve fibers plays more than a significant role in the work of the circulatory system.

Prevention

Against the backdrop of possibly complex information about what the heart is, it makes sense to pay a little attention to simple actions that will help keep it in working order for many years.

So, given what features the structure and work of the heart has, we can conclude that the health of this organ depends on the state of three elements: muscle tissue, blood vessels and blood flow.

In order for everything to be good with the heart muscle, you need to give it a moderate load. This mission is perfectly accomplished by jogging (without fanaticism) or walking. Such exercises temper the main organ of the circulatory system.

Now a little about the vessels. To keep them in shape, you need to eat right. This means that you will have to say goodbye to large and stable portions of fatty foods forever and correctly build your diet. The body must receive all the necessary nutrients and vitamins, then everything will be fine.

And the last guarantee of a long work of the heart, and of the whole body, is good blood flow. Here one simple secret will come to the rescue: all people have a thickening blood in the evening. And if we are talking about representatives of the middle age group, then such its consistency in some cases becomes dangerous, causing the risk of heart attack or stroke. Evening walks in the bosom of nature will help correct the situation. Where there are trees, lakes, sea, mountains or waterfalls, there is a high concentration of ionized air, which noticeably improves blood flow.

Conclusion

Based on all the information presented above, one can come to the obvious result: the innervation of the heart, the physiology of this organ and its work in general will always be important topics that do not lose their relevance. Indeed, without this knowledge, the level of which is constantly deepening, it is difficult to imagine an effective diagnosis and competent treatment of the heart.

The innervation of the heart is the supply of nerves that provide a connection between the organ and the central nervous system. While it sounds simple, it really isn't.

The main organ of the human circulatory system is the heart. It is hollow, resembles a cone, the location is the chest. If we describe its functions in simple words, then we can say that it works like a pump.

The peculiarity of the organ is that it can produce electrical activity on its own. This quality is defined called automation. Even a completely isolated heart muscle cell can contract on its own. In order for the body to work fully, this quality is necessary.

As mentioned above, the heart is located in the chest, the smaller part is localized on the right, and the larger on the left. So it is not worth thinking that the whole heart is located on the left, as this is wrong.

From childhood, children are told that the size of the heart is equal to the size of the hand, which is clenched into a fist, and this is actually the case. You should also be aware that the organ is divided into two halves, left and right. Each part has an atrium, a ventricle, and there is an opening between them.

Parasympathetic innervation

The heart receives not one, but several innervations at once - parasympathetic, sympathetic, sensitive. You should start with the first of all of the above.

Preganglionic nerve fibers can be classified as vagus nerves. They end in the intramural ganglia of the heart - these are nodes, which are a whole set of cells. The second neurons with processes are in the ganglia, they go to the conducting system, the myocardium and coronary vessels.

After excitation of the central nervous system, biologically active substances, as well as peptides, enter the synaptic cleft. This must be taken into account, since they have a modulating function.

Processes in progress

If we talk about the parasympathetic innervation of the heart further, then we cannot fail to note some important processes. You should know that the right vagus nerve affects heart rate, and the left one affects AV conduction. The innervation of the ventricles is poorly expressed, which is why the influence is indirect.

As a result of many complex processes, the following can occur:

Exit K + from the cell. The rhythm slows down, the refractory period decreases.
Protein kinase A activity is reduced. As a result, conductivity also decreases.

Attention should be paid to such a concept as the escape of the heart. This is a phenomenon in which the contraction stops due to the fact that the vagus nerve is excited for a long time. The phenomenon is considered unique, because this is how it is possible to avoid cardiac arrest.

Sympathetic innervation

It is almost impossible to describe the innervation of the heart briefly, all the more in language accessible to ordinary people. But dealing with the sympathetic is not so difficult, because the nerves are evenly distributed throughout the heart.

There are the first neurons called pseudo-unipolar cells. They are located on the lateral horns of the 5 upper segments of the thoracic spinal cord. The processes end in the cervical and upper nodes, the beginning of the second begins there, which in turn depart into the heart.

Sensitive innervation

It can be of two types - reflex and conscious.

Sensitive innervation of the first type is carried out as follows:

Nerve neurons of the spinal nodes... In the layers of the walls of the heart, receptor endings are formed by dendrites.
Second neurons... They are located in their own nuclei.
Third neurons... The site of localization is the ventrolateral nuclei.

Reflex innervation is provided by the neurons of the lower and upper nodes of the vagus nerves. Sensitive innervation is carried out with the help of Dogel's second type afferent cells.

Myocardium

The middle muscle layer of the heart is called the myocardium. This is the bulk of its mass. The main feature is contraction and relaxation. However, in general, the myocardium has four properties - conduction, contractility, excitability and automatism.

Each property should be considered in more detail:

Excitability... In simple terms, this is the heart's response to a stimulus. A muscle can only react to a strong stimulus; other forces will not be perceived. All this is because the myocardium has a special structure.
Conductivity and automatism... This is a unique feature of pacemaker cells to initiate spontaneous excitation. It appears in the conducting system, and then goes to the rest of the myocardium.
Contractility. This property is the easiest to understand, but there are some peculiarities here as well. Not many people know that the length of muscle fibers affects the strength of contraction. It is believed that the more blood flows to the heart, the more they stretch, respectively, the more powerful the contraction.

The health and condition of each person depends on the correctness of such a complexly arranged organ.

Muscle structure and blood flow

Above it was talked about what the parasympathetic, sympathetic and sensitive innervation of the heart is. The next point that is also important to consider is blood supply. It is not only difficult, but also interesting.

The human heart muscle is the very center of the blood supply process. Many people know at least approximately how the heart works. After the blood enters the organ, it passes into the atrium, then into the ventricle and large arteries. The biofluid movement is controlled by valves.

Interesting! Blood with low oxygen from the heart is sent to the lungs, where it is purified, and then saturated with oxygen.

After oxygenation, the blood flows into the venules, and then into the large veins. Through them, she goes back to the heart. In such a simple language, you can describe how the systemic circulation is organized.

Heart volume

There is cardiac output and systolytic volume. Concepts are directly related to blood supply and innervation. The amount of blood ejected by the stomach over a certain amount of time is called the minute volume of the heart. In an adult and completely healthy person, this is about five liters.

Important! The volume for the left and right ventricles is equal.

If the minute volume is divided by the number of muscle contractions, then a new name will be obtained - the notorious systolytic. The calculation is actually extremely simple.

The heart of a healthy person contracts up to 75 times per minute. This means that the systolytic volume will be equal to 70 milliliters of blood. But it is worth noting that the indicators are generalized.

Prevention

Against the background of the complex topic of the innervation of the heart, a little attention should be paid to what actions can preserve the functioning of the organ for long years.

Given the structural and operational features, it can be concluded that heart health depends on several main elements:

blood flow;
vessels;
muscle tissue.

In order for the heart muscle to be in order, a moderate load must be placed on it. Walking or jogging will help you accomplish this mission. Simple exercises can temper the main organ of the body.

In order for the vessels to be normal, it is important to normalize your diet. You will have to say goodbye to portions of fatty foods forever. The body must receive the necessary micronutrients and vitamins, only then everything will be fine.

If we are talking about representatives of the age group, then in some cases the consistency can be so dangerous that it can provoke a stroke or heart attack. In order to somehow correct the situation, it is useful to walk in the evening, breathe fresh air.

Based on the foregoing, we can conclude that everything in the human body is interconnected, one cannot exist without the other. The longer the heart is healthy, the longer a person can live and enjoy life.

Frequently asked questions to the doctor

Heart health

What are the most effective ways to keep your heart healthy?

In order for your heart to please you with its work for many years and not let you down, you need to follow a few simple rules:

proper nutrition;
rejection of bad habits;
preventive examinations;
movement, even if there is no strength at all.

If throughout your life you follow simple recommendations, you will hardly complain about the work of the organ.