What is the term for the pressure that ventricles must overcome to open the aortic and pulmonary valves?

The term that refers to the pressure the ventricles must overcome to open the aortic and pulmonary valves is afterload. Afterload represents the resistance that the ventricles face during systole, which is the phase of the heartbeat when the heart muscle contracts and pumps blood. Specifically, afterload involves the pressure in the aorta and pulmonary arteries that the ventricles must exert force against to eject blood during contraction.

Understanding afterload is crucial in the context of cardiac function because it significantly influences the heart's performance. An increase in afterload can make it more difficult for the heart to pump effectively, possibly leading to conditions like heart failure if the heart cannot compensate for this increased workload.

Preload, on the other hand, refers to the degree of stretching of the ventricular myocardium at the end of diastole, influenced by the volume of blood returning to the heart. Contractility is related to the intrinsic ability of the cardiac muscle to contract, independent of the preload and afterload. Venous return pertains to the passage of blood back to the heart and affects preload but does not directly refer to the pressure the ventricles need to overcome.