Final answer:
The amount of blood that returns to the heart during diastole is referred to as preload, or end diastolic volume (EDV), which significantly impacts the stroke volume and cardiac output.
Step-by-step explanation:
The amount of blood that returns to the heart during diastole is called preload. Preload, also known as end diastolic volume (EDV), is the amount of blood in the ventricles at the end of atrial systole just prior to ventricular contraction.
It is a crucial factor for the ventricles as it affects the stroke volume (SV) and, consequently, the cardiac output (CO).
Preload increases with an increase in the amount of venous returning to the heart, and it decreases when there's a decline in venous return.
Afterload, on the other hand, refers to the resistance the ventricles must overcome to pump blood out of the heart.