Question

The heart ventricles begins to fill when

Answer 1

[AI-generated answer — Bot GPT 3.5]

the atria contract and push blood into the ventricles. This is known as ventricular diastole, the relaxation phase of the cardiac cycle. As the ventricles fill with blood, they become stretched and their pressure increases. This stretches the heart muscle fibers, allowing them to contract more forcefully during ventricular systole, the pumping phase of the cardiac cycle.