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The role of the electrical system of the heart is:

  • To maintain an adequate heart rate (proportional to the energy expenditure of the body)
  • To coordinate the contraction of the atria and the ventricles in series
  • To coordinate the simultaneous contraction of the two atria and subsequently the two ventricles (especially the ventricles)

Components of the electrical system in the heart

The Sino-Atrial (SA) Node:
  • It is the command center for the coordination of all electrical activity
  • The cells of the SA node have the property of automaticity (depolarizing spontaneously)
  • These cells are under the influence of the autonomic nervous system
    • The sympathetic system (beta-adrenergic stimulation) increases the firing rate of the SA node
    • The parasympathetic system (acetylcholine stimulation) decreases the firing rate of the SA node
The Atrio-Ventricular (AV) Node:
  • It serves as the gateway for electrical transmission between the atria and the ventricles
  • It serves to insert an appropriate delay between atrial and ventricular contraction
  • It prevents the ventricles from being activated too rapidly in cases of excessively rapid atrial activation
Bundle of His:
  • A short segment of “electrical highway” connecting the AV node and the bundle branches
Bundle Branches:
  • Left and right bundle branches deliver the electrical current from the bundle of His to the left and right ventricle, respectively
Purkinje Fibers:
  • The bundle branches terminate in the myocardial tissue along the endocardium in Purkinje fibers