conduction system of the heart pdf basics

In the early embryonic heart tube, an ECG, similar to an adult ECG, can be recorded, indicating the presence of sequentially activated chambers.3 Given this observation, it is as confusing to accept the presence of a conduction system because it is functionally present as it is to deny its existence because it is not morphologically recognizable. The myocytes of the conduction system share with those of the ordinary working myocardium four basic elements: (1) contraction, (2) autorhythmicity, (3) intercellular conduction, and (4) electromechanical coupling. Classic reports cover the anatomy,1 pathology,1 and histology2 of the adult and developing conduction system. With a delay, the impulse is then rapidly transmitted from the AVN via the bundle branches and PPN to ensure a coordinated activation of the ventricular myocardium from apex to base. The impulse is subsequently conducted, via the atrial myocardium, which in this sense is part of the conduction pathway as well, toward the AVN. The SAN, which contains the leading pacemaker, generates the impulse. The conduction system comprises separate components with distinct functions. The atria contract a fraction of a second before the ventricles so their blood empties into the ventricles before the ventricles contract.In the formed heart, it is convention to distinguish working myocardium (the primary function of which is contraction) from the conduction system (the primary function of which is the generation and conduction of the electrical impulse). Normally at rest, as the electrical impulse moves through the heart, the heart contracts about 60 to 100 times a minute, depending on a person's age.Įach contraction of the ventricles represents one heartbeat. The bundle of His divides into right and left pathways, called bundle branches, to stimulate the right and left ventricles. There, impulses are slowed down for a very short period, then continue down the conduction pathway via the bundle of His into the ventricles. The electrical impulse travels from the sinus node to the atrioventricular node (also called AV node). The 2 upper chambers of the heart (atria) are stimulated first and contract for a short period of time before the 2 lower chambers of the heart (ventricles).

The electrical stimulus travels down through the conduction pathways and causes the heart's ventricles to contract and pump out blood. The sinus node generates an electrical stimulus regularly, 60 to 100 times per minute under normal conditions. This is a small mass of specialized tissue located in the right upper chamber (atria) of the heart. The heart's pumping action is regulated by an electrical conduction system that coordinates the contraction of the various chambers of the heart.Īn electrical stimulus is generated by the sinus node (also called the sinoatrial node, or SA node). Like all muscle, the heart needs a source of energy and oxygen to function. In the simplest terms, the heart is a pump made up of muscle tissue.

Conduction system of the heart pdf basics