Where does ventricular depolarization start within the heart structure?

Where does ventricular depolarization start within the heart structure?

• A. The epicardium
• B. The endocardial surface
• C. The myocardial layer
• D. The atrial surface

Answer: (B)

Ventricular depolarization primarily begins at the endocardial surface of the ventricles. The endocardium is the inner lining of the heart chambers and is where the electrical impulses trigger the contraction of the heart muscle cells. These impulses travel through the conduction pathways, specifically originating from the Purkinje fibers that are located close to the endocardial surface. The electrical signal then spreads through the myocardial layer, causing the ventricular myocardium to contract.

Understanding this mechanism is crucial for interpreting EKGs effectively, as the waves and intervals on an EKG directly represent the electrical activity associated with depolarization and repolarization within the heart. Specifying the endocardial surface highlights the initiation point of ventricular depolarization in relation to the entire heart structure.