<unk>  are otherwise known as atrioventricular bypass fibers that connect the atrial fibers to bundle of His by penetrating through the AV node.  These fibers are categorized as fibers that bypass through the normal conducting system.
James fibers
Mahaim fibers
Association fiber
Reticular fiber
Climbing fiber
Brechenmacher fibers
Purkinje fibers
Muscle fascicle