Atrioventricular node

The atrioventricular node is specialized cardiac tissue that conducts electrical impulses from the atria to the ventricles with a brief delay. This delay allows the ventricles to fill before they contract.

Cardiac conduction system: The network of specialized heart tissue that generates and conducts electrical impulses to coordinate cardiac contraction. The atrioventricular node is the pathway’s only normal electrical bridge between atria and ventricles.
Sinoatrial node: A group of cardiac cells that normally initiates each heartbeat and sets the heart’s rhythm. Its impulses activate the atria and normally arrive at the atrioventricular node.
PR interval: The electrocardiographic interval from the start of atrial depolarization to the start of ventricular depolarization. It reflects conduction through the atria, atrioventricular node, and His-Purkinje system.
Wolff–Parkinson–White syndrome: A pre-excitation syndrome in which an accessory pathway conducts impulses between atria and ventricles, bypassing the normal delay. Its accessory pathway can transmit atrial impulses without the node’s usual filtering delay.
Atrioventricular delay: The interval between atrial electrical activation and ventricular electrical activation. Slow conduction through the node creates this interval, allowing ventricular filling before contraction.
Atrial depolarization: The electrical activation of the atrial muscle that precedes atrial contraction. The atrioventricular node receives the impulse after it spreads through the atria.
Atrioventricular block: A delay or failure of electrical impulses to conduct from the atria to the ventricles. Impaired conduction through the node can produce several forms of atrioventricular block.
Accessory pathway: An abnormal electrical connection between cardiac chambers that bypasses part of the normal conduction system. Unlike the atrioventricular node, an accessory pathway can directly connect atrial and ventricular tissue.
Refractory period: A period after excitation when excitable tissue cannot, or is less able to, respond to another stimulus. The node’s refractoriness limits how many rapid atrial impulses reach the ventricles.
Atrioventricular junction: The region connecting atrial tissue to the His bundle, including the atrioventricular node and adjacent transitional tissue. The node is one part of this broader junctional region.

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