electrical activity in heart]

• control of basic heartbeat is myogenic- heart will beat without stimulus
• summary- heart contraction

  1. sinoatrial node(SAN) sends out a wave of excitation
  2. atria contracts
  3. atrioventricular node sends out wave of excitation
  4. purkyne tissue conducts wave is excitation
  5. ventricles contract
• complex stages

  1.SAN initiates a wave of depolarisation causing atria to contract

  • there is a region of non-conducting tissue which prevents depolarisation spreading straight to ventricles

  2. depolarisation then carried to atrioventricular node(AVN)

  3.after a slight delay, AVN is stimulated and passes stimulation along bundle of HIS

  • delay= ventricles contract after atria

  4.bundle of HIS:2 branches to either ventricles- Purkinje tissue/fibres spread around ventricles and initiates depolarisation of ventricles from bottom of heart= means ventricles contract bottom upwards-blood forced out
• SAN=a group of cells in the wall of the right atrium

  AVN= region of conducting tissue between atria and ventricles

  bundle of HIS=collection of conducting tissue in septum of the heart