The cardiac conduction system: generation and conduction of the cardiac impulse

The normal cardiac-conduction-system is responsible for the contraction of the heart muscle. Damage or irregular function of the cardiac conduction system can lead to serious and, in some cases, fatal clinical events. Every cardiac myocyte has the potential of contracting when stimulated with an adequate impulse. Electrical impulses are generated through changes in electrolyte concentration inside and outside pacemaker cells (a concentration gradient). The normal cardiac conduction system allows for, not only, the generation of this impulse but, also, its automatic propagation of it throughout the atrial and ventricular myocardium allowing for complete contraction of the heart muscle. In this paper we outline the key components behind the automated generation of the cardiac impulses and the effect these impulses have on cardiac myocytes. Also, a description of the key components of the normal cardiac-conduction- system is provided including the sinoatrial node, the atrioventricular node, the His Bundle, the Bundle branches and the Purkinje network. Other principles, including depolarisation and repolarisation of the myocardium and autonomic nervous system regulation, are also included. Finally, an outline of how each stage of the cardiac conduction system is represented on the electrocardiogram is described, allowing the reader to translate background information about the normal-cardiac conduction system to everyday clinical practice