What is the heart's activity during diastole?

During diastole, the heart undergoes a relaxation phase, which is crucial for the filling of the ventricles with blood. This phase begins after the heart has contracted and pumped blood out during systole. As the heart relaxes, the chambers—particularly the atria and ventricles—fill with blood from the veins. The pressure in the ventricles decreases, allowing the atrioventricular valves (the mitral and tricuspid valves) to open, thereby facilitating blood flow from the atria into the ventricles. This process is essential for ensuring that an adequate volume of blood is available for the next contraction, thus maintaining efficient circulation throughout the body.

The other processes mentioned in the other options occur at different times during the cardiac cycle. For example, vigorous contraction and ejection of blood take place during systole, while the generation of electrical signals primarily occurs in relation to the heart's own intrinsic conduction system and affects both phases, but isn’t a defining characteristic of diastole. Understanding these phases is critical in cardiology and for interpreting EKG findings correctly.