CARDIAC ELECTRICAL ACTIVITY-SPREAD OF EXCITATION

SUMMARY

1. Depolarization initiated at the SA node spreads radially through the atria, the converges via internodal pathways (anterior, middle, posterior) on the AV node.

2. AV node ⟹ bundle of His ⟹ right & left bundle branches ⟹ Purkinje fibers ⟹ all parts of the ventricles.

3. The interventricular septum is activated from left to right.

4. Depolarization spreads from apex to base of heart to reach the end of the Purkinje system, then from endocardium to epicardium.

5. The last parts of the heart to depolarized are pulmonary conus, top part of interventricular septum, basal & posterior parts of LV.

Reference(s)

Barrett, K.E., Barman, S.M., Brooks, H.L., X, J. and Ganong, W.F. (2019). Ganong’s review of medical physiology. 26th ed. New York: Mcgraw-Hill Education