An important characteristic of the work of the heart muscle is the automatism of contractions. The coordinated work of the heart, which is based on successive contractions and relaxations of the muscle tissue of the atria and ventricles, is regulated by a nerve impulse-conducting cellular structure with a complex structure.
The conduction system of the heart is the most important mechanism for ensuring the vital activity of the human body, consisting of a pulse generator (pacemaker) and individual complex formations designed to innervate the myocardial work cycles. Consisting of a cell structure, which is based on the work of P-cells and T-cells, it is designed to initiate a heartbeat and coordinate the contraction of the heart chambers. The first type of cells has an important physiological function of automation - the ability to rhythmic contraction without a pronounced connection with the influence of any external stimuli.
T cells, in turn, have the ability to transmit contractile impulses generated by P cells to the myocardium, which ensures its uninterrupted operation. Thus, the conducting system of the heart, the physiology of which is based on the coordinated interaction of these two groups of cells, is a single biological mechanism structurally entering the cardiac apparatus.
The conduction system of the human heart consists of several functional components: the sinoatrial and atrioventricular nodes, as well as the His bundle with right and left legs ending in Purkinje fibers. The sinoatrial (sinus) node, located in the region of the right atrium, is a small mass of muscle fibers of an ellipsoidal shape. It is in this component, from which the conduction system of the heart begins, that nerve impulses arise, causing contractile reactions of the whole heart. Normal automation of the sinoatrial node is considered to be from fifty to eighty pulses per minute.
The atrioventricular component, located below the endocardium in the posterior segment of the atrial septum, performs an important function of delaying, filtering and redistributing the incoming impulses generated and sent by the sinoatrial node. The conduction system of the heart also performs regulatory and distribution functions assigned to its structural component - the atrioventricular node.
The need for such functions is due to the fact that a wave of nerve impulses, instantly propagating through the atrial system and causing their contractile response, is not able to immediately penetrate the ventricles of the heart, since the atrial myocardium is separated from the ventricles by fibrous tissue that does not allow nerve impulses to pass through. And only in the area of the atrioventricular node is such an insurmountable barrier absent. This makes the wave of impulses in search of an outlet rush to this important component, where they are uniformly distributed throughout the cardiac apparatus.
The conduction system of the heart also contains in its structure a His bundle connecting the atrial and ventricular myocards, and Purkinje fibers that form synapses on cardiomyocyte cells and provide the necessary combination of muscle contraction and nervous excitement. At its core, these fibers are the final branching of the His bundle attached to the subendocardial plexuses of the ventricles of the heart.