tion:Hello..what is cardiac cycle❓The cardiac cycle is the sequence of events that occurs when the heart beats. As the heart beats, it circulates blood through pulmonary and systemic circuits of the body. There are two phases of the cardiac cycle. In the diastole phase, the heart ventricles are relaxed and the heart fills with blood. In the systole phase, the ventricles contract and pump blood out of the heart and to arteries. One cardiac cycle is completed when the heart chambers fill with blood and blood is then pumped out of the heart.Cardiac Cycle Phases :The events of the cardiac cycle described below trace the path of blood as it enters the heart, pumps to the lungs, travels back to the heart and is pumped out to the rest of the body. It is important to note that the events that occur in the first and second diastole periods actually happen at the same time. The same is also true for the events of the first and second systole periods.During the first diastole period, the atria and ventricles are relaxed and the atrioventricular valves are open. Oxygen-depleted blood returning to the heart from the body passes through the superior and inferior VENA cavae and flows to the right atrium. The open atrioventricular valves (TRICUSPID and mitral valves) allow blood to pass through the atria to the ventricles. Impulses from the sinoatrial (SA) node travel to the atrioventricular (AV) node and the AV node send signals that trigger both atria to contract. As a result of the contraction, the right atrium empties its contents into the right VENTRICLE. The tricuspid valve, located between the right atrium and right ventricle, PREVENTS blood from flowing back into the right atrium.