Chapter 19 2.0.pdf

19.3 – Cardiac Cycle ▪ Begins at atrial contraction and ends with ventricular relaxation ▪ Systole – pumping blood into circulation ▪ Diastole – chambers are relaxed and filling with blood 19.3 – Cardiac Cycle Phases ▪ Start with atria and ventricles relaxed – blood flows into atria and through into...

19.3 – Cardiac Cycle ▪ Begins at atrial contraction and ends with ventricular relaxation ▪ Systole – pumping blood into circulation ▪ Diastole – chambers are relaxed and filling with blood 19.3 – Cardiac Cycle Phases ▪ Start with atria and ventricles relaxed – blood flows into atria and through into ventricles (70% - 80%), semilunar valves are closed ▪ Atrial systole – atria contract from superior portion following depolarization (P wave), known as “atrial kick” ▪ Atrial diastole – muscles relax as ventricles begin to contract ▪ Ventricular systole – blood in ventricles is the end diastolic volume (EDV) or preload, it flows toward the atria forcing the atrioventricular valves to close (isovolumic contraction), pressure increases and forces the semilunar valves open 19.3 - Cycle ▪ Stroke volume – amount of blood pushed out by ventricles, normally 70 80 mL ▪ End systolic volume (ESV) – amount of blood left in ventricles after stroke volume is pushed out Ventricular Diastole – relaxation (T wave), semilunar valves close and atrioventricular valves are closed too (isovolumic ventricular relaxation phase). Second phase the atrioventricular valves open