Final answer:
The left ventricle does not empty completely during contraction; it ejects most of the blood but retains a volume known as the end systolic volume.
Step-by-step explanation:
The direct answer to when the left ventricle contracts is: b) No, it does not empty completely. During the cardiac cycle, ventricular systole refers to the phase where the ventricles contract and eject blood out of the heart. Specifically, during the ventricular ejection phase, the left ventricle does not empty fully. The volume of blood that remains in the ventricle after it has contracted is known as the end systolic volume (ESV).
Normally, the stroke volume—the amount of blood pumped by the left ventricle during a single beat—is around 70-80 mL, yet the ventricle begins with an end diastolic volume (EDV) of about 130 mL. Thus, an estimated 50-60 mL of blood, which is the ESV, still resides in the left ventricle post-contraction. This contraction allows for the complete emptying of blood from the left ventricle, ensuring efficient circulation throughout the body.