| Front | Describe the cardiac cycle |
|---|---|
| Back | 1. Ventricles relaxed, atria contract which leads to decreased volume and increased pressure. This causes blood to be flown into ventricles. There is increased ventricular pressure and chamber volume as ventricles receives ejected blood from contracting atria 2. Atria relax. Ventricles contract (volume decrease and pressure increases). Pressure in ventricles greater than atria so the atrioventricular valves shut. Pressure in ventricles greater than in the pulmonary artery and aorta which causes semi-lunar valves to open. 3.Ventricles and atria relax. Higher pressure in pulmonary artery and aorta closes the Semi-lunar valves to prevent back-flow of blood. Blood returns to heart and atria fill again due to higher pressure in vena cava and pulmonary vein. Increased pressure in atria. As ventricles relax the pressure falls below the pressure of atria so Atrioventricular valves open causing blood to flow passively into ventricles. |
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