Question

Place the muscle under the appropriate action: Extension vs Flexion?

1) Extension: Biceps brachii, Flexion: Triceps brachii
2) Extension: Triceps brachii, Flexion: Biceps brachii
3) Extension: Hamstrings, Flexion: Quadriceps
4) Extension: Quadriceps, Flexion: Hamstrings

Answer 1

Option 2) and 4). The correct placement of muscles under extension and flexion is that the triceps brachii extends the elbow, the biceps brachii flexes it, the quadriceps extend the knee, and the hamstrings flex it.

Step-by-step explanation:

Understanding that muscles function in pairs and can only contract, not extend, is necessary to properly place the muscle under the appropriate action of either flexion or extension. The biceps brachii and triceps brachii are two muscles in the human arm that work against each other to regulate the movement of the elbow joint. While the triceps brachii contracts as an extensor to straighten the elbow and open the limb, the biceps brachii contracts as a flexor to bend the elbow and close the limb. When it comes to the leg, the opposing muscle groups that cause knee movements are the quadriceps and hamstrings. The hamstrings serve as the flexor of the knee joint, contracting to bend the knee, and the quadriceps function as the extensor, contracting to straighten the knee. Therefore, the correct placements for the actions described are:

1. Extension: Triceps brachii, Flexion: Biceps brachii
2. Extension: Quadriceps, Flexion: Hamstrings.