Heart - LO 10

10. Understand the basics of the electrical conduction system of the heart.

There are two main types of structures associated with the electrical conduction system of the heart: nodal tissue and conducting fibers. Nodal tissue is responsible for initiating impulses (autorhythmic) that lead to contraction of the heart. The nodal tissue may be controlled extrinsically by the cardiac plexuses, and can be stimulated or inhibited by the sympathetic and parasympathetic systems, respectively. Conducting fibers will conduct the impulses initiated by the nodal tissues rapidly throughout the different areas of the heart.

Sinu-atrial (SA) node

• Largest collection of nodal tissue

• Located deep to epicardial layer in the superior portion of the crista terminalis

• Supplied by the sinu-atrial nodal br.

• Initiates impulses that spread to both atria

Atrioventricular (AV) node

• Located in interatrial septum near the coronary sinus opening

• Supplied by the AV nodal br.

• Sends signals to the AV bundle (of His), which splits into the right and left bundles around the interventricular septum

  • The bundles will branch into Purkinje fibers which conduct impulses through the ventricular walls (myocardium) and papillary mm.