<prompt> An increase in contractility is demonstrated on a Frank-Starling diagram byIncreased cardiac output for a given end-diastolic volumeIncreased cardiac output for a given end-systolic volumeDecreased cardiac output for a given end-diastolic volumeDecreased cardiac output for a given end-systolic volume  <response>: The frank-starling law of the hea states that when increased quantities of blood flow into the hea, the increased blood stretches the walls of the hea chambers. As a result of the stretch, the cardiac muscle contracts with increased force, and this action empties the extra blood that has entered from the systemic circulation. For the hea, the length of the muscle fibers ie, the extent of the preload is propoional to the end-diastolic volume. 