Understanding Cardiac Cycle & Function: Phases, Pressure-Volume Loops, Regulation - Prof. , Study notes of Biology

Download Understanding Cardiac Cycle & Function: Phases, Pressure-Volume Loops, Regulation - Prof. and more Study notes Biology in PDF only on Docsity! 24 February Lecture Objectives/Study Guide Learn the phases of the cardiac cycle Understand how pressure-volume loops are generated, how they describe cardiac function, and why this is important Understand how cardiac output is regulated The Cardiac Cycle Coordinated activity of the chambers and valves of the heart Atrial systole → isovolumetric contraction→ ventricular systole → ventricular diastole Phases of the Cardiac Cycle Inflow Isovolumetric contraction Outflow Isovolumetric relaxation Stroke volume = end-diastolic volume – end-systolic volume Ejection fraction = SV/EDV Same things happen on left and right side of heart, but right side is lower pressure Contractility of the heart = cardiac performance How to evaluate in the clinic? The end-systolic pressure-volume relationship (ESPVR) is used most frequently to describe cardiac contractility Afterload – pressure against which heart has to pump (aorta) Cardiac Pressure-Volume (PV) Loops LV volume (mL) vs LVP (mmHg) on graph Makes a loop – Left side isovolumteric relaxation, bottom ventricular filling, right side isovolumetric contraction, top ejection 1. P and V at the end of ventricular filling As the ventricle begins to contract but before the aortic valve opens, LVP increases by LV volume remains the same. Isovolumetric contraction 2. When LVP exceeds aortic diastolic pressure, the aortic valve opens and ejection of blood occurs. 3. The aortic valve closes, ejection ceases Isovolumetric relaxation 4. When the LVP falls below left atrial pressure, the mitral valve opens and the ventricle begins to fill. Once the ventricle is fully relaxed, the LVP gradually increases as the LV volume increases. Key Points The width of the loop represents the difference between EDV and ESV = SV Systole/diastole? Ejection fraction? Regulation of Cardiac Function