What does afterload refer to in relation to cardiac function?

Correct answer: False

Preload refers to the degree of stretch of the ventricular myocardial fibers at the end of diastole, just before ventricular contraction. It is influenced by the volume of blood returning to the heart (venous return) and the compliance of the ventricular walls. End-diastolic volume (EDV) is the actual volume of blood present in the ventricle at the end of diastole. While preload is closely related to EDV, it is a functional measure of myocardial fiber stretch rather than a direct measurement of blood volume. Thus, preload describes the mechanical tension on the myocardium, whereas EDV quantifies the volume of blood in the chamber.

Correct answer: True

The sinoatrial (SA) node, located in the upper wall of the right atrium near the entrance of the superior vena cava, serves as the heart’s natural pacemaker by generating electrical impulses. These impulses spread through specialized internodal pathways across the atrial walls, causing atrial depolarization and contraction. The impulses then converge at the atrioventricular (AV) node, situated in the lower interatrial septum near the tricuspid valve, which briefly delays the signal to allow the atria to empty completely into the ventricles. This pathway ensures coordinated atrial and ventricular contraction, maintaining efficient cardiac output.