Mark the following statements as true or false. If the statement is false, correct it to make a true statement.
The pectoralis major and coracobrachialis muscles are antagonists.

Verified step by step guidance

1. Step 1: Understand the concept of antagonistic muscles. Antagonistic muscles are pairs of muscles that perform opposite actions. For example, one muscle contracts to move a joint in one direction, while the other muscle contracts to move the joint in the opposite direction.
2. Step 2: Identify the actions of the pectoralis major muscle. The pectoralis major is a large chest muscle responsible for actions such as flexion, adduction, and medial rotation of the humerus at the shoulder joint.
3. Step 3: Identify the actions of the coracobrachialis muscle. The coracobrachialis is a smaller muscle located in the upper arm that assists in flexion and adduction of the humerus at the shoulder joint.
4. Step 4: Compare the actions of the two muscles. Since both the pectoralis major and coracobrachialis contribute to flexion and adduction of the humerus, they perform similar actions rather than opposing actions.
5. Step 5: Conclude that the statement is false and correct it. The pectoralis major and coracobrachialis muscles are not antagonists; they are synergists because they work together to perform similar actions at the shoulder joint.

Key Concepts

Antagonistic Muscles

Antagonistic muscles are pairs of muscles that work against each other to create movement. When one muscle contracts, the other relaxes, allowing for controlled motion. For example, the biceps and triceps are antagonists; when the biceps contract to flex the elbow, the triceps relax.

Pectoralis Major

The pectoralis major is a large, fan-shaped muscle located in the upper chest. It is primarily responsible for movements such as shoulder flexion, adduction, and internal rotation. Understanding its function is crucial for identifying its role in arm movements and its relationship with other muscles.

Coracobrachialis

The coracobrachialis is a small muscle located in the upper arm, originating from the coracoid process of the scapula. It assists in flexing and adducting the arm at the shoulder joint. Recognizing its function helps clarify its relationship with the pectoralis major and why they are not antagonists.