ATI Pathophysiology Practice Exam

Which muscle is affected when straightening the elbow by lowering the hand?

1. Biceps brachii

2. Triceps brachii

3. Deltoid

4. Pronator teres

The correct answer is: Triceps brachii

When straightening the elbow by lowering the hand, the muscle primarily involved is the triceps brachii. This muscle is responsible for extension at the elbow joint. During the action of straightening the elbow, the triceps contract, which allows the forearm to move outward and extend away from the upper arm. The biceps brachii, on the other hand, is mainly responsible for flexion at the elbow, acting when you bend the arm to bring the hand closer to the shoulder. The deltoid is primarily engaged in shoulder movements rather than elbow extension or flexion. Lastly, the pronator teres is involved in the pronation of the forearm rather than in the extension or straightening of the elbow. Thus, the triceps brachii’s role is crucial for the action of straightening the elbow effectively.