BIOL-242 Lecture Notes - Lecture 13: Heart Valve, Pulmonary Artery, Stroke Volume
6 May 2020
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Chapter 18 part 4 | cardiac cycle and stroke volume. Phases of the cardiac cycle: ventricular filling // takes place mid-to-late relaxation. End diastolic volume (edv) : volume of blood in each ventricle at end of ventricular diastole: ventricular systole // all valves closed, ventricle begins to contract, ejection. Rising ventricular pressure closing of av valves. Isovolumetric contraction phase (all valves are closed) In ejection phase, ventricular pressure exceeds pressure in large arteries, forcing sl valves open. End systolic volume (esv) : volume of blood remaining in each ventricle after systole: isovolumetric relaxation // early relaxation. Backflow of blood in aorta and pulmonary trunk closes sl valves. Causes dicrotic notch (brief rise in aortic pressure as blood rebounds off closed valve) When atrial pressure exceeds that in ventricles av valves open; cycle begins again at step 1. As soon as blood leaves the ventricle, the pressure goes down . Lub // closure of atrioventricular valve; beginning of systole.
