🫀 The Car

Notes

🫀 The Cardiac Cycle: Mechanical Events The cardiac cycle represents all the mechanical events occurring during a single heartbeat. Understanding this cycle involves new terminology and the interplay of pressure and valve action. Key Terminology ● ● ● Systole: Contraction. For example, atrial systole refers to atrial contraction. Diastole: Relaxation. This is when the heart muscle returns to its resting state. Pressure Differential: Valves open when there is a greater pressure on one side of the valve compared to the other, allowing blood to flow in one direction. Valves prevent backflow, so blood cannot move against the intended direction even with a pressure differential. Four Steps of the Cardiac Cycle The cardiac cycle is a continuous, cyclical process. Although presented as four sequential steps, it's a dynamic continuum where one stage seamlessly transitions into the next, eventually bringing the heart back to the first step. 1. Ventricular Filling This is the initial step where the ventricles fill with blood. 1. Valve Status: ○ AV (Atrioventricular) Valves: Open. Blood flows freely from the atria to the ventricles. ○ Semilunar Valves: Closed. This prevents blood from enterin...