Final answer:
The cardiac cycle consists of periods of relaxation (diastole) and contraction (systole) of the heart chambers, facilitating blood circulation. Cardiac diastole involves the filling of relaxed chambers with blood, whereas atrial systole is when the atria contract to transfer blood to the ventricles.
Step-by-step explanation:
Cardiac Cycle: Diastole and Systole
The question pertains to the phases of the cardiac cycle, specifically cardiac diastole and atrial systole. The cardiac cycle includes periods of contraction (systole) and relaxation (diastole) of the heart chambers, ensuring efficient blood flow through the heart and entire body. Cardiac diastole is the phase when all heart chambers are relaxed, allowing blood to flow into the heart. Atrial systole follows, where the atria contract to push blood into the ventricles. Afterward, during ventricular systole, the ventricles contract and pump blood out of the heart.
During cardiac diastole, both atria and ventricles are in a relaxed state, the atrioventricular valves are open, permitting blood to move from the major veins into the relaxed atria and subsequently into the ventricles. As the pressure in the ventricles falls below that in the atria, blood naturally flows into the ventricles, prepping them for the next cycle. Then, atrial systole begins, with atrial contraction that leads to the pushing of blood into the ventricles, followed by ventricular systole, where the ventricles contract to eject blood from the heart to the lungs and the rest of the body. This carefully regulated process entails beats per minute, depending on the individual's heart rate.