In which category of muscle of muscle contraction the filament that move to shorten a muscle are

Options

A. Skeletal muscle fibre
B. Cardiac muscle fibre
C. Smooth muscle fibres
D. All of these

Answer

To answer the question regarding the category of muscle contraction in which the filaments move to shorten a muscle, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Types of Muscle Fibers**: There are three main types of muscle fibers: skeletal muscle fibers, cardiac muscle fibers, and smooth muscle fibers.

2. **Understand Muscle Contraction**: Muscle contraction involves the shortening of muscle fibers, which is primarily achieved through the interaction of two types of filaments: actin (thin filament) and myosin (thick filament).

3. **Apply the Sliding Filament Theory**: According to the sliding filament theory, during muscle contraction, the actin and myosin filaments slide past each other. This sliding action leads to the shortening of the muscle fiber.

4. **Focus on Skeletal Muscle Fibers**: Skeletal muscle fibers are responsible for voluntary movements, such as walking and running. The contraction of these fibers results in movement at the joints.

5. **Conclusion**: Based on the sliding filament theory and the role of skeletal muscle fibers in producing movement, we can conclude that the category of muscle contraction where the filaments move to shorten a muscle is **skeletal muscle fibers**.

### Final Answer:
The correct answer is **skeletal muscle fibers**.

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