PHSI 208 Lecture Notes - Lecture 28: Heart Valve, Cardiac Cycle, Cardiac Muscle
Document Summary
Cardiac cycle = one complete contraction and relaxation. Two primary phases: diastole = the time during which cardiac muscle relaxes, systole = the time during which cardiac muscle contracts. Because the atria and ventricles do not contract and relax at the same time the events are discussed separately. The heart contracts and relaxes during a cardiac cycle. Pressure volume loop of cardiac cycle (systemic circuit) Wigger"s diagram = a comprehensive view at a single cardiac cycle. Looks at the ecg, the pressure in the outflow arteries, ventricles and atria, and the changes in volume. D: atria and ventricles relaxes, pressure in atria begins to exceed ventricle. Av valve opens and you get the passive filling of the ventricle (change in volume in ventricle seen from f on) Atria then contracts increasing the volume and pressure slightly (atria contraction only contributes 20% of blood) C: ventricle beings to contract, increasing pressure within ventricle causing the av valves to snap shut (s1)
