Bundle is a group of nerve or muscle fibers.
atrioventricular b. A bundle of specialized muscular fibers located in the membranous interventricular septum of the heart; the only direct muscular connection between the atria and the ventricles; it originates at the atrioventricular node in the floor of the right atrium, extends downward in the septum, divides into right and left branches, and ends in numerous strands in the papillary and ventricular muscles. Also called bundle of His.
b. of His See atrioventricular bundle.
posterior longitudinal b. See medial longitudinal fasciculus, under fasciculus.