Heart - Pump and Crossing Paths

The heart can be considered a real crossroads of highways, a regulator of the “movement” of blood, since veins and arteries converge in it, and it continuously acts as a pump. The heart works in two types of movements: systolic, or contraction movement, and diastolic, or relaxation movement. The cycle of heart activity, what we usually call a beat, consists of three phases:

1. Atrial systole and ventricular diastole. When the atria contract, the mitral and tricuspid valves open and blood flows into the ventricles.

2. Ventricular systole. The ventricles contract, causing blood pressure to rise. The semilunar valves of the aorta and pulmonary artery open and the stomachs empty through the arteries.

3. Total diastole. After emptying, the ventricles relax and the heart remains in the resting phase until blood filling the atrium presses on the atrioventricular valves.

Excitation of the heart occurs due to muscle nodular tissue, more precisely, muscle cells specialized in excitation of the heart muscle. This tissue consists of the sinoatrial node and the atrioventricular node, located in the right atrium. In the first of these nodes, electrical impulses arise that cause the heart to contract (70-80 contractions per minute), and then the second node is excited, which can independently force the heart to beat (40-60 contractions per minute). Through the His bundle and Purkinje fibers, excitation spreads to both ventricles.