thaler chapter 1

1   The Basics

24

2. Anterior fascicle , which runs along the anterior wall of the left ventricle 3. Posterior fascicle , which sweeps over the posterior wall of the left ventricle The right bundle branch and the left bundle branch and its fascicles terminate in countless tiny Purkinje fibers, which resemble little twigs coming off the branches of a tree. These fibers deliver the electrical current into the ventricular myocardium.

Bundle of His AV node

Left bundle branch

Right bundle branch

Left anterior fascicle Septal fascicle

Left posterior fascicle

Purkinje fibers

Ventricular myocardial depolarization causes ventricular contraction. It is marked by a large deflection on the EKG called the QRS complex . The amplitude of the QRS complex is much greater than that of the atrial P wave because the ventricles have so much more muscle mass than the atria. The QRS complex is also more complicated and variable in shape than the P wave, reflecting the greater intricacy of the pathway of ventricular depolarization. The ventricular conduction system, shown in detail. Below the bundle of His, the conduction system divides into right and left bundle branches. The right bundle branch remains intact, whereas the left divides into three separate fascicles.