7. ECG timing & scale

• ecg picture

  
• P wave:

  • atrial depolarisation, starting @ the SA node and reading through both artria
• PR interval:

  • the time the action potential takes to travel from the SA node through the AV node to the ventricles.
  • reflects atrial depolarisation and AV node delay
• QRS comple:

  • ventricular depolarisation, starting @ the bundle of his/atrioventricular bundle and spreads to the Purkinje fibres
• T wave:

  • ventricular repolarisation
• Atrial repolarisation:

  • occur during QRS complex but not visible due to its small amplitude and bing overshadowed by the QRA complex