Basics of Cardiac Arrythmias
- The Atrioventicular Node
- Location and activity
- Atrioventicular node (AV node) is located on the interatrial septum close to the tricuspid valve. It receives impulses from the SA node and conducts them to the bundle of His. Conduction through the AV node is slow providing a deliberate delay that allows the ventricles you fill up (after atrial contraction) before the ventricles contract.
- The electric impulse from the SA must be conducted though the AV node
because the atria and ventricles are separated by a fibrous connective tissue septum that
has poor conductivity. The AV node provides the path of least resistance for the impulse
to proceed to the ventricles.
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- AV rhythm
- The AV node together with the bundle of His make up the AV junctional tissue. The AV junctional tissue has its own intrinsic pacemaker activity at of 40-60 beast per minute. If the SA nodes are injured AV junctional tissue can take over control of heart rate and rhythm.
- Why must the electric impulse be conducted though the AV node
- The electric impulse from the SA node is conducted though the AV node because the atria and ventricles are separated by a fibrous connective tissue ring that has poor conductivity. The AV node provides a path for the impulses to proceed from the atria to the ventricles.
- Potential role of the AV node in protecting the ventricles
- In pathological circumstances involving atrial fibrillation, the impulses arrive at the AV node at a very high rate (up to 300 impulses a minute). Since the AV node has a long refractory period, some of these impulses find the AV node refractory and are not conducted to the ventricles. Therefore, the AV node functions in a protective role, preventing ventricular fibrillation which can be quickly fatal.
- Last Updated: 01/03/00.
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