Question

question 21

the pacemaker cells of the heart are located in the

a) purkinje fibers.
b) sa node.
c) av node.
d) wall of the left ventricle.
e) both the left and right ventricles.

Explanation:

Identify the primary pacemaker of the heart

The heart's electrical conduction system contains specialized cells that generate and propagate electrical impulses. The primary pacemaker cells, which establish the normal sinus rhythm of the heart, are located in the sinoatrial (SA) node.

Locate the sinoatrial (SA) node

The SA node is situated in the superior wall of the right atrium, near the opening of the superior vena cava. It spontaneously depolarizes at a faster rate than other components of the conduction system, thereby driving the heart rate.

Evaluate the other options

• Purkinje fibers and the AV node are parts of the conduction system but act as secondary or latent pacemakers, only taking over if the SA node fails.
• The ventricular walls consist of contractile myocardium rather than primary pacemaker cells.

Answer:

• (A) Purkinje fibers.
• (B) SA node. (Correct answer)
• (C) AV node.
• (D) wall of the left ventricle.
• (E) both the left and right ventricles.