How is blood pumped by the heart?

There are 3 main phases in the cardiac cycle: Diastole, Atrial systole, Ventricular systole 1.Diastole: -The heart fills with blood as the atria and ventricles relax. -Blood flows from the major veins(vena cava to the right side and pulmonary vein to left) into the atria and into the ventricles via the open atrioventricular valves. -AV valves are open because of the pressure gradient. The pressure is higher in the atria than in ventricules. The semi lunar valves are closed because pressure in the ventricles is lower than in the arties leading away from the heart. 2.Atrial systole: -The begninning of muscles contraction. As the atria contract , more blood is pushed into the ventricles. 3.Ventricular systole -Ventricles contact, increasing ventricular pressure. Blood pushes against AV valves and since pressure is now higher in the ventricles than in the atria, the AV valves shut, preventing blood from flowing back to atria (also known as the 'lub' in the 'lub-dub' sound of the heart). -The pressure in the ventricles continues to increses until it is greater than the pressure in the main arties leading from heart. The semin lunar vavlves then open and blood rushed out of ventricles and into the artieties. -After the ventricles have finished contracting, muscles relax and are pulled back by elastic tissue. The decrease in pressure in the ventricles causes the semi lunar valves to shur and the AV valves to open so the diastole phase takes place again. The process of a heartbeat 1.A heart beat begins at the Sino atrial node which is located above the right atrium. Its role is to generate electrical pulse in a regular manner, which spreads throughout heart. 2. Once an electrical excitation has been generated by the sinoatrial node, it spreads throughout the atrial muscles, which then contact as part of atrial systole. 3.The wave of excitation is stopped however by a non-conducting disc of tissue at the base of the atria. This prevents the wave from causing the ventricles to contract too early. The only path to the ventricles is through another node called the Atrioventricular Node. 4.At the atrioventricular node, the electrical pulse is delayed to allow theatria to fully contract. Then the wave travels down the inter-ventricular wall through special conducting tissue known as the Purkyne, towards the apex (base) and the ventricular muscles. 5.As the wave reaches the muscles, it initiates the contraction. The wave then moves up the ventricles from the apex causing further contraction. In this manner the contraction of the ventricles starts at the bottom and moves upwards, so that blood is forced upwards into the arteries during ventricular systole.