Question

What happens when the pacemaker becomes non-functional?

• A. Only auricles contract rhythmically
• B. Only ventricles contract rhythmically
• C. Cardiac muscles do not undergo co-ordinated rhythmic movements
• D. Auricles and ventricles contract rhythmically

Answer 1

The correct option is C Cardiac muscles do not undergo co-ordinated rhythmic movements

C. Cardiac muscles do not undergo coordinated rhythmic movements

Reason: The contraction of atria is initiated and activated by the sinoatrial node (SA node – pacemaker). Which spreads waves of contraction across the walls of the atria via muscle fibers at regular intervals.

An artificial pacemaker has the function to send electrical impulses from the atrium for contraction and pumping action into the ventricles. SA node has maximum rhythmicity. So, if the pacemaker becomes non-functional then, cardiac muscles do not undergo coordinated rhythmic movement.