Questions: Cardiac action potentials usually originate in cells. A chordae tendinae (B) Purkinje (C) pacemaker (D) septal

The answer is (C) pacemaker.

Explanation for each option:

A) Chordae tendinae: These are tendinous cords that connect the papillary muscles to the tricuspid and mitral valves in the heart. They do not generate action potentials.

B) Purkinje: These are specialized conducting fibers in the heart that help propagate action potentials quickly throughout the ventricles, but they do not originate the action potentials.

C) Pacemaker: The pacemaker cells, primarily located in the sinoatrial (SA) node, are responsible for initiating cardiac action potentials. These cells generate spontaneous electrical impulses that set the rhythm for the heart.

D) Septal: This term refers to the septum, which is the wall dividing the left and right sides of the heart. While it contains conducting pathways, it is not the origin of cardiac action potentials.

In summary, cardiac action potentials usually originate in pacemaker cells, specifically in the sinoatrial node.