Heart

• What does myogenic mean?

  • The muscle will contract and relax on its own accord however the rate it contracts is controlled by a wave of electricity from the nervous system 
• What is the sionatrial node (SAN)?

  • A pace maker located in the right atrium
• What is the atrioventricular node (AVN)?

  • Pace maker cell located between right atrium and left ventricle
• What is the bundle of hiss?

  • Tissue that runs down the septum
• What are purkyne fibers?

  • In the walls of the ventricles
• Can you explain the control of heart rate?

  • SAN releases a wave of depolarisation (electricity) causing the atria to contract
  • Reaches AVN and releases a wave of depolarisation
  • Non conductive layer between the atria and ventricle which prevents the wave of depolarisation reaching the ventricle
  • Instead, bundle of hiss conducts the wave down the septum and purkyne fibers
  • This causes a delay between the atria contraction and apex ventricle contraction
  • This allows time for all the blood to enter the ventricles
  • Cells repolarise and cardiac muscle relaxes
• How does the brain control heart rate?

  • Sinoatrial node increases heart rate via sympathetic nervous system
  • Decreases heart rate by parasympathetix nervous system