Control of the cardiac cycle

• label the diagram

  A) sinoatrial node (pacemaker)

  B) right atrium

  C) purkyne tissue (or fibres)

  D) bundle of his

  E) atrioventricular node

  F) atrio-ventricular septum

  
• what is the role of the sinoatrial node (SAN)?

  • also called the pacemaker
  • initiates the cardiac cycle by generating an electrical impulse called a 'wave of excitation'
• what is the role of the atrioventricular node (AVN)?

  • delays the wave of excitation to ensure the atria finish contracting, before passing it onto the Bundle of His
• what is the role of the Bundle of His/ Purkyne fibres?

  • specialised highly conductive fibres, which pass the wave of excitation down to the bottom of the ventricles
• what is the role of the atrioventricular septum?

  • a layer of non-conductive tissue between the atria and the ventricles, that blocks the wave of excitation
• what happens during the cardiac cycle?

  • SAN initiates WOE
  • WOE passes over both atria
  • WOE causes atria to contract
  • blood pumped from atria to ventricles
  • atria relax
  • non-conductive tissue stops electrical impulse
  • AVN delays wave to allow atria to contract
  • WOE passed from AVN to bundle of his to purkyne fibres - highly conductive
  • WOE passed from purkyne fibres to ventricles
  • WOE causes ventricles to contract
  • higher pressure in ventricles causes AV valve to close
  • blood pumped out of ventricles into arteries
  • ventricles relax
  • higher arterial pressure causes SL valve to close
• what is the apex?


  very bottom of heart