The functional unit of the contractile system in the striped muscle is_____

Answer

**Step-by-Step Solution:**

1. **Understanding Striped Muscles**: Striped muscles are characterized by the presence of striations. These muscles include skeletal muscles and cardiac muscles, while smooth muscles do not have striations.

2. **Function of Muscles**: The primary function of muscles is contraction and relaxation, which allows movement.

3. **Composition of Muscle Fibers**: Muscle fibers are made up of smaller units known as sarcomeres.

4. **Structure of Sarcomeres**: Sarcomeres consist of two main types of proteins:
- **Actin**: This is a thin filament that includes two actin filaments, along with tropomyosin and troponin proteins. These proteins play a role in muscle contraction by binding with myosin.
- **Myosin**: This is a thick filament characterized by its globular head, which has two important binding sites: one for actin and one for ATP (adenosine triphosphate), which provides energy for muscle contraction.

5. **Function of Sarcomeres**: When sarcomeres come together, they form muscle fibers, which are responsible for the contractile function of striped muscles.

6. **Conclusion**: Therefore, the functional unit of the contractile system in striped muscle is the **sarcomere**.

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