Electrophysiology
| Structure | Function and Location |
|---|---|
| Sinoatrial (SA) node | This node is the dominant pacemaker of the heart, located in the upper portion of the right atrium. Intrinsic rate is 60–100 bpm. |
| Internodal pathways | These cells direct electrical impulses between the SA and AV nodes and spread them across the atrial muscle. |
| Atrioventricular (AV) node | This node is part of an area called AV junctional tissue, which includes some surrounding tissue plus the connected bundle of His. Although AV junctional tissue contains pacemaker cells, none are thought to exist in the AV node itself. The AV node slows conduction, creating a slight delay before electrical impulses are carried to the ventricles. Intrinsic rate is 40–60 bpm. |
| Bundle of His | Also known as the AV bundle, this specialized tissue is located at the top of the interventricular septum and fibers extend directly from the AV node and connect the atria and ventricles electrically. |
| Bundle branches | The bundle of His splits into two conduction paths called the right and left bundle branches. These bundles carry electrical impulses at high speed to the tissue of the interventricular septum, and to each ventricle simultaneously. |
| Purkinje system | The bundle branches terminate with this network of fibers, which spread electrical impulses rapidly throughout the ventricular walls. The intrinsic rate is 20–40 bpm. |
Electrophysiology
| Action | Effect |
|---|---|
| Depolarization | The electrical charge of a cell is altered by a shift of electrolytes on either side of the cell membrane. This change stimulates muscle fiber to contract. |
| Repolarization | Chemical pumps re-establish an internal negative charge as the cells return to their resting state. |
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