BIOLOGY 20 Lecture Notes - Lecture 21: Stroke Volume, Coronary Artery Disease, Cardiac Cycle
Document Summary
Cardiac cycle the period between the start of one heartbeat and the beginning of the next. Steps in the cardiac cycle: atrial systole. Right and left av valves are opens: atria eject blood into ventricles. Known as end-diastolic volume (edv: ventricular systole. Isovolumetric contraction all 4 valves are shut for a very brief period of time. Blood flows into pulmonary and aortic trunks. Stroke volume (sv) + 60% of end-diastolic volume: ventricular pressure falls. Ventricles contain end systolic volume (esv), about 40% of end diastolic volume: ventricular diastole. Ventricular pressure is higher than atrial pressure. Ventricles relax (isovolumetric relaxation) all 4 valves are shut for a very brief period of time: atrial pressure is higher than ventricular pressure. Caused by a sudden deceleration of blood flow into the lv from the la. Occurs early in diastole and normal phenomenon in young people and athletes.
