3.4.2.2 Cardiac Cycle

• Systole = the contraction of the heart, when the heart pumps blood out of the ventricles
• Diastole = relaxation of the heart, when the heart relaxes and fills with blood
• Overview of Steps of Cardiac Cycle

  1. Cardiac Diastole
  2. Atrial Systole & Ventricular Diastole
  3. Ventricular Systole
• 1. Blood enters atrium via the vena cava
  2. Some blood "trickles" down into ventricle
  3. Atrial Systole (atrial wall muscle contracts) decreasing the volume & increasing the pressure
  4. Ventricular Systole (ventricle wall muscle contracts) forcing atrioventricular valves to close increasing pressure in ventricle
  5. Blood is forced up & out of arteries
  6. Diastole occurs increasing the chamber vomune & decreasing the pressure
  7. Semilunar valves close