Final answer:
During the cardiac cycle, the left ventricle's pressure drops and volume remains initially constant in early diastole, followed by volume increase as blood fills the ventricle. In systole, pressure rises, leading to ventricular contraction without volume change, followed by volume decrease as blood is ejected.
Step-by-step explanation:
At the beginning of ventricular diastole, the left ventricle's pressure drops as the ventricle relaxes, signifying the isovolumic ventricular relaxation phase. The end diastolic volume (EDV) remains unchanged initially because the atrioventricular valves are still closed, preventing blood from entering the ventricle. In the second phase or late ventricular diastole, ventricular pressure falls below atrial pressure. This difference in pressure causes the atrioventricular valves to open, allowing blood to flow into the ventricles, which increases the ventricular volume.
Conversely, during ventricular systole, the ventricular muscle contracts, increasing pressure inside the ventricle. This phase of the cardiac cycle has two stages: isovolumic contraction, where the ventricle contracts but does not eject blood, maintaining a constant volume, and the ventricular ejection phase, where the increased pressure forces the semilunar valves open, and blood is expelled into the arterial system, dropping the volume down to the end systolic volume (ESV). The left ventricle generates higher pressures than the right due to higher resistance in the systemic circulation compared to the pulmonary circuit. However, both ventricles eject an equal stroke volume of blood, approximately 70-80 mL per contraction.