Cardiac conduction system

The cardiac conduction system is specialized heart tissue that generates and conducts electrical impulses, coordinating the timing of atrial and ventricular contractions.

Sinoatrial node: A cluster of pacemaker cells in the right atrium that normally initiates each heartbeat. Its spontaneous electrical activity starts the impulse that spreads through the conduction system.
Cardiomyocyte: A contractile muscle cell of the heart that generates force in response to electrical activation. Conduction ultimately coordinates these cells' contractions.
Electrocardiography: The recording of the heart's electrical activity from electrodes placed on the body surface. An electrocardiogram displays electrical events produced as impulses travel through the heart.
Ectopic pacemaker: A site outside the sinoatrial node that generates impulses capable of activating the heart. It can take over when impulses arise from an abnormal location instead of the usual origin.
Atrioventricular node: Specialized tissue between the atria and ventricles that slows electrical conduction before ventricular activation. Its delay gives the ventricles time to fill after the atria contract.
Intercalated disc: A specialized junction between cardiac muscle cells that provides mechanical attachment and electrical coupling. Electrical coupling lets activation spread from one cardiac cell to another.
Electrocardiogram: A tracing of voltage changes recorded from the heart over time using surface electrodes. Its waves and intervals provide a surface view of conduction timing.
Atrioventricular reentrant tachycardia: A rapid heart rhythm sustained by an electrical reentry circuit involving the atrioventricular node or nearby pathways. Reentry turns conduction into a self-sustaining loop rather than a one-way sequence.
Bundle of His: A conducting tract that carries impulses from the atrioventricular node into the interventricular septum. It provides the normal electrical route from atria to ventricles.
Gap junction: A channel between adjacent cells that permits ions and small molecules to pass directly between them. Gap junctions enable rapid electrical communication within cardiac tissue.

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