Z line or Krause membrane is present in the

Options

A. I band
B. A band
C. H band
D. Both (1) & (2)

Answer

**Step-by-Step Solution:**

1. **Understanding the Z line (Krause membrane)**: The Z line, also known as the Krause membrane, is a structure found in muscle fibers. It serves as a boundary that separates adjacent sarcomeres, which are the basic contractile units of striated muscle.

2. **Identifying the types of muscle fibers**: The Z line is specifically found in striated muscle fibers, which include skeletal and cardiac muscles. These muscles have a distinct banding pattern due to the arrangement of actin and myosin filaments.

3. **Recognizing the bands in muscle fibers**: Muscle fibers are organized into alternating bands:
- **I-band**: This is the isotropic band, which appears lighter under a microscope and contains only thin filaments (actin).
- **A-band**: This is the anisotropic band, which appears darker and contains both thick (myosin) and thin (actin) filaments.
- **H-band**: This is a lighter region in the A-band where there are only thick filaments.

4. **Determining the location of the Z line**: The Z line is located at the center of the I-band. It bisects the I-band and connects to the thin filaments.

5. **Evaluating the options**:
- **Option 1 (I-band)**: Correct, as the Z line is located in the I-band.
- **Option 2 (A-band)**: Incorrect, as the Z line is not found in the A-band.
- **Option 3 (H-band)**: Incorrect, as the Z line is not found in the H-band.
- **Option 4 (Both 1 and 2)**: Incorrect, since the Z line is only present in the I-band.

6. **Conclusion**: The correct answer to the question is that the Z line (Krause membrane) is present in the I-band.

**Final Answer**: The Z line or Krause membrane is present in the I-band.

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