The cardiac cycle

• What does the cardiac cycle refer to?

  Events during a single heartbeat
• How long does the cardiac cycle last?

  About 0.8 seconds
• What are the three main stages of the cardiac cycle?

  1. Atrial Systole
  2. Ventricular Systole
  3. Diastole
• What happens during atrial systole?

  Atria contract, forcing blood into ventricles
• How long does atrial systole last?

  Around 0.1 seconds
• What is the final stage of ventricular filling?

  Atrial contraction
• What valves are involved in atrial systole?

  Atrioventricular valves: tricuspid and bicuspid
• What happens during ventricular systole?

  Ventricles contract, increasing pressure
• How long does ventricular systole last?

  Around 0.3 seconds
• What prevents backflow of blood into the atria during ventricular systole?

  Closure of the AV valves
• What do the semilunar valves do during ventricular systole?

  They open to allow blood flow
• What does the pulmonary artery carry?

  Deoxygenated blood to the lungs
• What does the aorta carry?

  Oxygenated blood to the body
• How long does diastole last?

  Around 0.4 seconds
• What happens during diastole?

  Atria and ventricles relax
• What causes the semilunar valves to close during diastole?

  Pressure in ventricles falls below aorta
• What happens to the AV valves during diastole?

  They open as atria fill with blood
• What are the key points to remember about the cardiac cycle?

  • Atrial systole: Atria contract → blood moves to ventricles
  • Ventricular systole: Ventricles contract → blood moves to lungs & body
  • Diastole: Relaxation → heart fills with blood (no contraction)
• How can you visualize the cardiac cycle?

  • Atrial Systole: Atria contract → blood flows into ventricles
  • Ventricular Systole: Ventricles contract → blood pumped into aorta and pulmonary artery
  • Diastole: Heart relaxes → blood fills atria
• What is the function of the AV valves and semilunar valves?

  • AV valves: Prevent backflow into atria during ventricular systole
  • Semilunar valves: Prevent backflow into ventricles after blood is pumped out
• What is the total duration of the cardiac cycle?

  0.8 seconds per beat
• What is the duration of atrial systole?

  0.1 seconds
• What is the duration of ventricular systole?

  0.3 seconds
• What is the duration of diastole?

  0.4 seconds
• What mnemonic can help remember the cardiac cycle stages?

  • A → Atria contract = Atrial systole
  • V → Ventricles contract = Ventricular systole
  • D → Diastole = Don’t pump, relax