When a skeletal muscles shortens during contraction, which of these statements is false?

Options

A. The I-bands shorten
B. The A-bands shorten
C. The H-bands shorten
D. The sarcomeres shorten

Answer

To determine which statement is false regarding skeletal muscle contraction, we need to understand the structure of a sarcomere and the changes that occur during contraction.

### Step-by-Step Solution:

1. **Understand Muscle Contraction**: When a skeletal muscle contracts, the sarcomeres, which are the basic units of muscle fibers, shorten. This is a key aspect of muscle contraction.

2. **Identify Sarcomere Components**: The sarcomere consists of various bands and zones:
- **A Band**: The dark band that contains thick filaments (myosin).
- **I Band**: The light band that contains thin filaments (actin).
- **H Zone**: The area within the A band where there are only thick filaments.

3. **Analyze the Statements**:
- **Statement 1**: "The I band is shortened." This is true because during contraction, the I band decreases in size.
- **Statement 2**: "The I band remains the same." This is false because the I band does not remain the same; it shortens during contraction.
- **Statement 3**: "The H zone is shortened." This is true as well; the H zone decreases in size during contraction.
- **Statement 4**: "The sarcomere is shortened." This is also true since the entire sarcomere shortens during contraction.

4. **Conclusion**: The false statement among the options is that "the I band remains the same." This statement contradicts the physiological changes that occur during muscle contraction.

### Final Answer:
The false statement is: **"The I band remains the same."**

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