NURSING ANM AND GNM

Detailed explanation-1: -In cardiac physiology, isometric contraction is an event occurring in early systole during which the ventricles contract with no corresponding volume change (isometrically). This short-lasting portion of the cardiac cycle takes place while all heart valves are closed.

Detailed explanation-2: -Since blood is not being ejected from the ventricles at this early stage, the volume of blood within the chamber remains constant. Consequently, this initial phase of ventricular systole is known as isovolumic contraction, also called isovolumetric contraction (see image below).

Detailed explanation-3: -The first occurs during ventricular systole, when shortening of the ventricular muscle pulls the tricuspid valve ring toward the apex of the heart. This movement of the valve ring tends to increase atrial volume and decrease atrial pressure, thus increasing flow from the extracardiac veins into the atrium.

Detailed explanation-4: -The isovolumetric contraction causes left ventricular pressure to rise above atrial pressure, which closes the mitral valve and produces the first heart sound. The aortic valve opens at the end of isovolumetric contraction when left ventricular pressure exceeds aortic pressure.