An increase in sympathetic stimulation of the heart would increase stroke volume by increasing View Available Hint(s) end systolic volume heart rate end diastolic volume contractility Submit

To determine how an increase in sympathetic stimulation of the heart affects stroke volume, let's analyze the options provided: 1. **End Systolic Volume (ESV)**: This is the volume of blood remaining in the ventricles after contraction. An increase in sympathetic stimulation typically decreases ESV because the heart contracts more forcefully, ejecting more blood. 2. **Heart Rate (HR)**: While sympathetic stimulation does increase heart rate, this does not directly increase stroke volume. Stroke volume is primarily influenced by the volume of blood ejected with each heartbeat. 3. **End Diastolic Volume (EDV)**: This is the volume of blood in the ventricles just before contraction. An increase in sympathetic stimulation can lead to increased venous return, which may increase EDV, but this is not the primary mechanism for increasing stroke volume. 4. **Contractility**: This refers to the strength of the heart's contraction. Increased sympathetic stimulation enhances contractility, leading to a more forceful contraction and thus increasing stroke volume. Given this analysis, the correct answer is: **Contractility** Increased sympathetic stimulation of the heart increases stroke volume primarily by increasing contractility.