Cardiac Conduction System
Electrical conduction system coordinating rhythmic heart contraction.
Overview
The cardiac conduction system generates and propagates electrical impulses for coordinated heart contraction. The SA node (pacemaker) spontaneously depolarizes via HCN channels (funny current, If) and T-type/L-type Ca²⁺ channels. Impulses propagate through atrial myocytes to the AV node (which introduces a delay), then rapidly through the His bundle, bundle branches, and Purkinje fibers to the ventricular myocardium. Gap junctions (connexin 43) enable rapid cell-to-cell conduction.
Cellular Location
SA node → AV node → His bundle → Purkinje fibers → Ventricular myocardium
Clinical Significance
Ion channel mutations cause long QT syndrome, Brugada syndrome, and familial AF; antiarrhythmic drugs classified by channel targets (Vaughan-Williams); pacemakers replace SA node dysfunction.