The function of the heart is a rhythmic pumping in the artery blood flowing to him from the veins. This function is performed through alternate rhythmic contractions and relaxation of muscle fibres that make up the wall of the Atria and ventricles. Myocardial contractility of these parts of the heart called them systole and relaxation - diastole.
Systole and diastole the Atria and ventricles in normal physiological conditions in a certain way agreed between themselves and make up the cycle of work of heart. The beginning of each cycle believe the systole fibrillation. Reduction begins in the part of the right atrium, which houses the mouth hollow vein. Then wave reduction covers both Atria, which are General muscles. Systole fibrillation, the heart rate 75 per minute, continues 0.1 second. At the end of atrial systole begins ventricular systole, the Atria same time are in a state of ongoing 0.7 seconds diastole. Both ventricles contract simultaneously, and their systole lasts about 0.3 seconds. After that begins ventricular diastole, continued for about 0.5 seconds. At the end of diastole ventricles, for 0.1 seconds before the end, there comes a new atrial systole and begins a new cycle of cardiac activity.
Interplay and consistency of the reductions of the Atria and ventricles depend on where and how it is distributed agitation in the heart.