Which of the following are not antagonistic muscles?

Options

A. Flexor and extensor
B. Pronator and supinator
C. Abductor and adductor
D. Protractor and supinator

Answer

To determine which of the following are not antagonistic muscles, we need to understand the concept of antagonistic muscles. Antagonistic muscles are pairs of muscles that produce opposite movements at the same joint. Let's analyze the options step by step.

### Step-by-Step Solution:

1. **Understand Antagonistic Muscles**:
- Antagonistic muscles are those that work in opposition to each other. For example, when one muscle contracts, the other muscle relaxes to allow movement.

2. **Evaluate the First Option - Flexor and Extensor**:
- **Flexor**: This muscle type bends a limb (e.g., biceps).
- **Extensor**: This muscle type straightens a limb (e.g., triceps).
- **Conclusion**: Flexors and extensors are antagonistic muscles.

3. **Evaluate the Second Option - Pronator and Supinator**:
- **Pronator**: This muscle turns the palm downward (e.g., pronator teres).
- **Supinator**: This muscle turns the palm upward (e.g., supinator).
- **Conclusion**: Pronators and supinators are also antagonistic muscles.

4. **Evaluate the Third Option - Abductor and Adductor**:
- **Abductor**: This muscle pulls a limb away from the midline (e.g., deltoid).
- **Adductor**: This muscle brings a limb towards the midline (e.g., latissimus dorsi).
- **Conclusion**: Abductors and adductors are antagonistic muscles.

5. **Evaluate the Fourth Option - Protractor and Supinator**:
- **Protractor**: There is no recognized muscle classification as "protractor" in functional muscle classification.
- **Supinator**: As previously mentioned, this muscle turns the palm upward.
- **Conclusion**: Since "protractor" is not a recognized muscle type and does not have an opposing action to the supinator, this pair does not represent antagonistic muscles.

### Final Answer:
The correct answer is **the fourth option: Protractor and Supinator** are not antagonistic muscles.

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