KIN 292 1nd Edition Lecture 23 Outline of Last Lecture I 13 1 overview of the cardiovascular system II 13 2 pathway of blood flow through the heart III 13 3 anatomy of the heart IV 13 4 electrical activity of the heart Outline of Current Lecture I 13 4 Electrical Activity of the Heart continued II 13 5 The Cardiac Cycle Current Lecture 13 5 Cardiac cycle Events associated with the flow of blood through the heart during a single complete heartbeat Two main periods of cardiac cycle Systole ventricle contraction Diastole ventricle relaxation Valves open passively due to pressure gradients AV valves open when atrial pressure ventricular pressure Semilunar valves aortic and pulmonary open when ventricular pressure arterial pressure Know o Phases of the cardiac cycle o Atrial and ventricular pressure o Aortic pressure o Ventricular volume o Heart sounds o ECG EKG from lab Phase One These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Ventricular filling o Middle of ventricular diastole o Venous return o AV valve opens o Blood moves from atria to ventricle o Pulmonary and aortic valves are closed o Passive until atrium contracts Phase Two Isovolumetric ventricular contraction o Start of systole o Ventricle contracts increases pressure o AV and semilunar valves closed o No blood entering or exiting ventricle Phase Three Ventricular ejection Remainder of systole Pressure in ventricles pressure in arteries Semilunar valves open Ventricular pressure aortic pressure Semilunar valves close Phase Four Isovolumetric ventricular relaxation Onset of diastole Ventricle relaxes decreases pressure AV and semilunar valves closed No blood entering or exiting ventricle Atrial and Ventricular Pressure Phase 1 Atrial pressure rises slowly with filling of blood Ventricular pressure is low Small rise in VP at end due to atrial contraction Phase 2 Rapid rise in ventricular pressure Atrial pressure falls Phase 3 Ventricular pressure falls Atrial pressure falls further until late systole Aortic Pressure Diastole Starts when Aortic valve closes Backflow of blood in aorta causes slight increase dicrotic notch Blood is still leaving aorta so pressure falls Lowest point diastolic pressure Systole Aortic valve opens Pressure rises rapidly with ejection Highest point systolic pressure Aortic valve closes Pulsatile flow from heart to large arteries is converted to continuous flow by artery properties Aorta and large arteries elastic Pressure reservoir Stores energy during systole as walls expand Releases energy during diastole as walls recoil inward Aortic pressure maintains blood flow through the entire cardiac cycle Ejection fraction EF fraction of end diastolic volume ejected during a heartbeat EF stroke volume end diastolic volume EF 70 mL 130 mL 0 54 i e 54 at rest First heart sound Soft lubb AV valves close simultaneously at isovolumetric contraction Second heart sound Louder dupp Semilunar valves close simultaneously at isovolumetric relaxation
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