Heart sounds: Phonocardiogram



Cardiac cycle

 The impulse for heart beat originates in the SA node and causes the atria to contract first, atrial systole followed by the ventricles, ventricular systole. After contraction the chambers go into diastole, which is the period of relaxation and blood fills the chambers during this period.

Courtsey: Mariana Ruiz Villarreal


Normal ECG wave: Animation

 The heartbeat originates in a specialized cardiac conduction system and spreads via this system to all parts of the heart muscle. The structures that form the conducting system are the sinoatrial node (SA node); anterior, middle and posterior internodal tracts; the atrioventricular node (AV node); the bundle of His; right and left bundle branches; anterior-superior and posterior-inferior brances of the left bundle; and the Purkinje network. Conduction speeds in cardiac tissue

  • SA node - 0.05 m/s
  • Atrial pathways - 1 m/s
  • AV node - 0.05 m/s
  • Bundle of His - 1 m/s
  • Purkinje system - 4 m/s
  • Ventricular muscle - 1 m/s 
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