What defines the end-diastolic volume in cardiac function?

The end-diastolic volume is defined as the volume of blood in the ventricles at the end of diastole, right before the heart contracts. This measurement reflects the total amount of blood that has filled the ventricles during the relaxation phase of the cardiac cycle. It is crucial in understanding cardiac output and overall heart function, as a higher end-diastolic volume often contributes to a greater stroke volume during the subsequent contraction, provided the heart is functioning normally.

Other options do not directly define end-diastolic volume. The amount of blood ejected from the left ventricle pertains to stroke volume, which is determined after contraction has occurred. Contraction strength relates to how effectively the heart can pump blood but does not specify the volume present before the heart's contraction. The frequency of heartbeats, or heart rate, affects how often the heart cycles through its phases but does not define the volume present in the heart at any given time.