Final answer:
During ventricular diastole, blood flows into the heart while the ventricles are relaxed. During atrial systole, the atria contract and push blood into the ventricles.
Step-by-step explanation:
During ventricular diastole, the tricuspid and mitral (bicuspid) valves are open to allow blood to flow from the atria into the ventricles. The ventricles are in a relaxed state during this phase.
During atrial systole, the atria contract, pushing blood into the ventricles. At this stage, the tricuspid and mitral valves are open, facilitating the flow of blood from the atria to the ventricles.
It's important to note that the term "atrial systole" is somewhat unconventional, as systole typically refers to ventricular contraction. However, in this context, it is used to describe the contraction of the atria.