End diastolic volume would increase with which physiological change?

End diastolic volume would increase with which physiological change?

• A. Increased venous return
• B. Decreased venous return
• C. Decreased blood volume
• D. Increased heart rate

Answer: (A)

End diastolic volume is set by how much blood returns to and fills the ventricles during relaxation (the preload). When venous return increases, more blood flows into the heart during diastole, so the ventricles fill more and end up with a larger volume at the end of filling. This is why EDV rises with higher venous return. Think of the preload as the stretch on the heart before it contracts: more fill means more stretch and a stronger next contraction (the Frank-Starling mechanism). Conversely, lowering venous return—or reducing overall blood volume—reduces filling and lowers EDV. A faster heart rate can shorten diastole and limit filling time, which can decrease EDV, not increase it. So the best choice is increased venous return.

End diastolic volume is set by how much blood returns to and fills the ventricles during relaxation (the preload). When venous return increases, more blood flows into the heart during diastole, so the ventricles fill more and end up with a larger volume at the end of filling. This is why EDV rises with higher venous return.

Think of the preload as the stretch on the heart before it contracts: more fill means more stretch and a stronger next contraction (the Frank-Starling mechanism). Conversely, lowering venous return—or reducing overall blood volume—reduces filling and lowers EDV. A faster heart rate can shorten diastole and limit filling time, which can decrease EDV, not increase it.

So the best choice is increased venous return.