Multiple choice

If the pace maker is absent,

  1. only auricles will contract

  2. only ventricles will contract

  3. cardiac muscles will contract in a coordinated manner

  4. cardiac muscles will not contract in a coordinated manner
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The pacemaker (sinoatrial node or SA node) generates rhythmic electrical impulses that coordinate cardiac muscle contraction. Without the SA node, cardiac muscle cells would contract independently and asynchronously, leading to uncoordinated, ineffective heart pumping. The heart would lose its rhythmic, synchronized beating pattern.

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