An increase in venous return will _______.

An increase in venous return will _______.

• A. Decrease EDV
• B. Increase EDV and therefore increase stroke volume
• C. No change to EDV or stroke volume
• D. Increase heart rate but not stroke volume

Answer: (B)

The question tests how venous return affects ventricular filling and the subsequent pumping strength of the heart. When more blood returns to the heart, more fills the ventricles during diastole, raising the end-diastolic volume (EDV). This extra stretch of the ventricular muscle fibers increases the force of contraction according to the Frank-Starling mechanism, so the stroke volume rises. That’s why increasing venous return leads to a higher EDV and a higher stroke volume. The other possibilities don’t fit this sequence: increasing venous return does not decrease EDV; it does change EDV and does change stroke volume rather than leaving them unchanged; and while heart rate can be modulated by autonomic reflexes, the immediate effect of greater venous return is on filling and contraction, not a standalone increase in heart rate without changing stroke volume.

The question tests how venous return affects ventricular filling and the subsequent pumping strength of the heart. When more blood returns to the heart, more fills the ventricles during diastole, raising the end-diastolic volume (EDV). This extra stretch of the ventricular muscle fibers increases the force of contraction according to the Frank-Starling mechanism, so the stroke volume rises. That’s why increasing venous return leads to a higher EDV and a higher stroke volume.

The other possibilities don’t fit this sequence: increasing venous return does not decrease EDV; it does change EDV and does change stroke volume rather than leaving them unchanged; and while heart rate can be modulated by autonomic reflexes, the immediate effect of greater venous return is on filling and contraction, not a standalone increase in heart rate without changing stroke volume.