The cardiac cycle

• What are the three stages of the cardiac cycle?

  Atrial systole, ventricular systole, diastole.
• Atrial systole:

  • Atria fill up with blood, increasing pressure
  • The atrioventricular valves open and blood flows into ventricles
  • The atrial walls contract
• Ventricular systole:

  • Ventricles contract from the base upwards as they fill with blood
  • Pressure increases in ventricles
  • The semi-lunar valves open
  • The atrioventricular valves close
• Diastole:

  • Atria and ventricles relax
  • Pressure decreases
  • Atria fill with blood again
  • Blood in arteries flows toward ventricles again
  • Coronary artery fills, supplying the heart with oxygen