Physiology of the heart

The function of the heart is pumping blood from the veins in the artery and ensuring its constant movement. This is achieved by the rhythmic contractions of the heart. The contraction of the heart (systole) alternates with its relaxation (diastole). The heart is reduced automatically. In its conduction system agitation (pulse), which applies to attack and calls its reduction. Normally, these impulses arise in sinus node through an almost equal time intervals 60-80 times per 1 minute, where they are infarction fibrillation and cause them to fall. Systole fibrillation continues 0.1 sec. Next pulse passes through the site Asifa - Tavares, reaches the bundle of his, and his legs spread on the heart ventricles, causing them to fall.
Upon transfer of momentum to the ventricles, the speed of its spread is reduced, so atrial systole have time to finish before the end of stimulation of ventricles and begins their reduction. Systolic ventricular lasts about 0.3 seconds. and replaced them with diastole, the duration of which depends on the frequency of heart rhythm (on average about 0.5 seconds). Function automatic characteristic of almost all the conduction system, so in some diseases (see Arrhythmias) impulses to the reduction may occur in the beam Guisa and Purkinje fibers.
The sequence of the heart following. During ventricular systolic blood pressure in their cavities increases, resulting slam atrioventricular valves and opens the valve of aorta and pulmonary trunk; the ventricles cast contained in them blood to the aorta and the pulmonary trunk. With the beginning of the ventricular diastole pressure of blood in their cavities begins to fall, and when it is smaller than in the aorta and the pulmonary trunk, semilunar valves, the aorta and the pulmonary trunk closed, preventing the flow of the blood from the aorta and the pulmonary trunk back into the ventricles of the heart. At the same time open atrioventricular valves, and the blood of the Atria, diastole that begins shortly before ventricular diastole, and then from the venous system in, simply through relaxed atrium into the ventricles. Approximately 0,15 sec. until the next ventricular systolic begins systole fibrillation, which is pumped into the ventricles are in the Atria blood; then cardiac cycle starts again.
Since the pressure in the aorta is 4-5 times higher than in the pulmonary trunk, the left ventricle during systole have to develop a much greater voltage than the right. Intracardiac pressure in heart cavities also differ (for example, in the left ventricle during systole it reaches 110-130 mm RT. century, in the right ventricle - 25-30 mm RT. Art.). In heart disease pressure in the cavity may increase. In these cases, the myocardium of the Department of the heart, where the pressure is increased, it is necessary to contract with more force, which leads to a compensatory increase in muscle mass of the Department of the heart (compensatory hypertrophy of myocardium). During the beats of ventricular heart goeth not out about 70 ml of blood (drums, or systolic volume). 1 minute each ventricle throws from 3 to 5 liters of blood (minute volume). The intensive work the minute volume can exceed 25 L. Although the heart itself generates impulses to reduce, its activity is controlled by the nervous system. The increased influence at the heart of wandering nerve slows down the production of pulses in the sinus node, inhibits their conduct, reduces the number of heartbeats. The increased influence on the heart of the sympathetic nervous system increases anxiety attack, accelerates the production of pulses in the sinus node and increases the number of contractions of the heart.