Multiple choice

What constitutes a heartbeat?

  1. Rhythmic relaxation only

  2. Rhythmic contraction only

  3. Rhythmic contraction and relaxation

  4. None of the above

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The walls of the chambers of the heart are made up of muscles. These muscles contract and relax rhythmically. This rhythmic contraction followed by its relaxation constitute a heartbeat.