Final answer:
Increased pressure in the ventricles would close the atrioventricular valves, preventing blood from being forced back into the atria.
Step-by-step explanation:
Increased pressure in the ventricles would close the atrioventricular valves. When the ventricles begin to contract, the pressure within the ventricles rises and blood flows toward the area of lowest pressure, initially in the atria. This backflow causes the cusps of the tricuspid and mitral valves to close, preventing blood from being forced back into the atria.