Conduction system

• Sino Atrial (SA) node


  • Initiates cardiac cycle
  • Generates electrical impulse
  • Fires impulse through the atria walls causing atrial systole (atria contract) forcing remaining blood into ventricles
  • Sends impulse to AV node
• Atrio ventricular (AV) node


  • Receives impulse from SA node
  • Delays it for approx. 0.1 seconds to allow atria to finish contracting
  • Send impulse to bundles of His
• Bundles of His


  • Receives impulse from AV node
  • Carry impulse down the septum of the heart
• Bundle branches


  • Left and right bundle branches distribute the impulse to the base of each ventricle
• Purkinje fibres


  • Distribute impulse through ventricle walls causing ventricular systole (ventricles contract) forcing blood from ventricles into aorta + pulmonary artery
• Electrical impulse generation and transmission in the heart

  1. SA node creates/ fires/ generates an electrical impulse which passes through the atria walls

  2. This causes atrial systole/ contraction of atria

  3. AV node delays the electrical impulse which allows complete atrial systole

  4. Bundle of his/ Bundle branches/ Purkyne fibres pass the electrical impulse through the ventricle walls

  5. This causes ventricular systole/ contraction of ventricles

  6. No electrical impulse causes diastole/ relaxation of the heart/ cardiac muscle