As the volume of blood in the ventricles of the heart increases, with all other factors constant, stroke volume increases till a point. Explain why. (5)

Define stroke volume as the volume of blood expelled by the left ventricle into the aorta per contraction of the heart.Idea that as blood volume in the ventricle increases, this stretches the sarcomeres of cardiac muscle.Idea this increased sarcomere stretch removes mechanical interference and/or allows more actin-myosin cross bridges to form.Each cross-bridge generates a unit force; with more cross-bridges, a greater force is generated per contraction of the ventricle.A greater force of contraction leads to a greater volume of blood being expelled per contraction (hence the increased stroke volume).