Question

which of the following describes atrial systole? the atria contract, forcing any remaining atrial blood into the ventricles the ventricles contract, forcing any remaining ventricle blood into the atria the atria and ventricles contract, forcing blood into the aorta the atria and ventricles relax, allowing both to fill with blood

Explanation:

Atrial systole is the contraction phase of the atria. During this phase, the atria contract to force any remaining blood into the ventricles. The other options are incorrect: ventricles contracting to force blood into atria is not a normal process (valves prevent backflow); atria and ventricles don't contract simultaneously in a coordinated normal heartbeat for forcing blood into aorta (ventricles contract after atria); atria and ventricles relaxing is diastole (filling phase), not systole (contraction phase).

Answer:

the atria contract, forcing any remaining atrial blood into the ventricles