In cardiac histology, the conduction system of the heart is composed of specialized cardiac muscle cells — the sinoatrial node, atrioventricular node, atrioventricular bundle, and Purkinje fibers — rather than nervous tissue, and these cells are distinguished histologically by pale cytoplasmic staining (due to reduced contractile protein content) and, in Purkinje fibers, binucleation. The sinoatrial node functions as the heart's intrinsic pacemaker, generating rhythmic contraction autonomously, while its firing rate can be modulated externally by the autonomic nervous system and other factors. This concept belongs to cardiac histology/physiology and relates to the broader discipline by explaining the structural basis for the heart's autonomous, modulable electrical activity.
In cardiac histology, the conduction system of the heart is composed of specialized cardiac muscle cells — the sinoatrial node, atrioventricular node, atrioventricular bundle, and Purkinje fibers — r…