What happens in the heart?

So the heart is split in 4 main chambers. The Right Atrium, The Right Ventricle, The Left Atrium and The Left Ventricle. [Keep in mind, in a diagram the left of it is the right atrium, ventricle etc...] The Blood flows into the atriums via the Pulmonary vein or the Vena Cava [also a vein] The atriums contract, pushing the blood into the ventricles. The ventricles contract, forcing the blood to the Pulmonary artery or the Aorta. This keeps repeating itself again and again...