Conductive system of the heart. Innervation of the heart.
The so-called cardiac conduction system plays an important role in the rhythmic work of the heart and in the coordination of the muscles of the individual chambers of the heart. Although the muscles of the atria are separated from the muscles of the ventricles by fibrous rings, however, there is a connection between them by means of the conduction system, which is a complex neuromuscular formation. The muscle fibers that make up it (conductive fibers) have a special structure: their cells are poor in myofibers and rich in sarcoplasm, therefore lighter. They are sometimes visible to the naked eye in the form of light colored threads and represent a less differentiated part of the original syncytium, although they are larger in size than the ordinary muscle fibers of the heart. In the conducting system there are knots and bundles.
1. The sinoatrial node, nodus sinuatrialis, is located in the wall section of the right atrium corresponding to the cold-blooded sinus venosus (in sulcus terminalis, between the superior vena cava and the right ear). It is associated with atrial musculature and is important for their rhythmic contraction.
2. The atrioventricular node, nodus atrioventricularis, is located in the wall of the right atrium, near the tricuspid cuspis septalis. Fibers of the node, directly connected with the muscles of the atrium, continue into the septum between the ventricles in the form of the atrioventricular bundle, fasciculus atrioventricularis (His bundle). In the septum of the ventricles, the bundle is divided into two legs – crus dextrum et sinistrum, which go into the walls of the co-named ventricles and branch under the endocardium in their muscles. The atrioventricular bundle is very important for the functioning of the heart, since it transmits a wave of contraction from the atria to the ventricles, thereby establishing regulation of the rhythm of systole — the atria and ventricles.
Consequently, the atria are interconnected by the sinoatrial node, and the atria and the ventricles are connected by the atrioventricular bundle. Usually, irritation from the right atrium is transmitted from the sinus node to the atrioventricular node, and from it through the atrioventricular bundle to both ventricles.