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Question

Difficulty: EasySupport Structures and Locomotion

During the bending (flexion) of the human forearm at the elbow joint, which of the following muscular actions occurs?

  1. The biceps muscle contracts while the triceps muscle relaxesAnswer
  2. B
    The triceps muscle contracts while the biceps muscle relaxes
  3. C
    Both the biceps and triceps muscles contract simultaneously
  4. D
    Both the biceps and triceps muscles relax simultaneously

Answer

The biceps muscle contracts while the triceps muscle relaxes.
Skeletal movement at joints is produced by antagonistic muscle pairs. During flexion (bending) of the forearm at the elbow joint, the biceps muscle (flexor) contracts to pull the bone forward, while the triceps muscle (extensor) relaxes to allow the movement to take place.

Step-by-Step Solution

1
Identify the movement described in the stem
The movement is forearm flexion (bending the elbow joint).
Flexion decreases the angle between the upper arm and forearm.
2
Determine the role of the antagonistic muscle pair involved
The biceps acts as the flexor (agonist) and the triceps acts as the extensor (antagonist).
Muscles can only pull when contracting; movement requires paired opposing actions.
3
Match muscle states required for flexion
Contraction of the biceps produces the upward pull, while relaxation of the triceps permits motion.
Antagonistic coordination ensures smooth directional movement across synovial joints.

Key Concept

Antagonistic Muscle Action in Locomotion
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Topics

Support Structures and Locomotion

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