Question

which of the following is the correct sequential path of an action potential in the heart?
multiple choice
sinuatrial node, atrioventricular node, atrioventricular bundle, bundle branches, subendocardial branches (purkinje fibers)
atrioventricular node, sinuatrial node, atrioventricular bundle, bundle branches, subendocardial branches (purkinje fibers)
atrioventricular bundle, atrioventricular node, sinuatrial node, bundle branches, subendocardial branches (purkinje fibers)
subendocardial branches (purkinje fibers), atrioventricular bundle, atrioventricular node, sinuatrial node, bundle branches
atrioventricular node, sinuatrial bundle, atrioventricular node, bundle branches, subendocardial branches (purkinje fibers)

Explanation:

The sinoatrial (SA) node is the heart's natural pacemaker. It initiates the action potential. The impulse then travels to the atrioventricular (AV) node, which slows the signal slightly to allow the atria to contract fully before the ventricles. From the AV node, the action potential moves through the atrioventricular bundle (bundle of His), then into the bundle branches (right and left), and finally to the subendocardial branches (Purkinje fibers) which rapidly distribute the impulse throughout the ventricular myocardium, causing ventricular contraction. The other options have incorrect starting points (e.g., starting with AV node instead of SA node) or incorrect sequences.

Answer:

Sinuatrial node, atrioventricular node, atrioventricular bundle, bundle branches, subendocardial branches (Purkinje fibers)