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Which of the following statements about ...

Which of the following statements about the striated muscles is ture ?
In the centre of each I-Band is an elastic fiber(Z-line ) which bisects it
M-line is a fibrous memebrane in the middle of A bonds
Thin filament are firmly attached to the M-line
A sarcomere comprises one full A - bonds

A

ii

B

iv

C

`i and iii`

D

`i and ii`

Text Solution

AI Generated Solution

The correct Answer is:
To determine which statements about striated muscles are true, let's analyze each statement step by step. ### Step 1: Analyze the First Statement **Statement:** In the center of each I-Band is an elastic fiber (Z-line) which bisects it. - **Explanation:** The I-band is the light band in striated muscle fibers, primarily composed of actin filaments. The Z-line (or Z-disc) is indeed located in the center of the I-band and serves as an anchor point for the thin filaments (actin). Therefore, this statement is **true**. ### Step 2: Analyze the Second Statement **Statement:** M-line is a fibrous membrane in the middle of A bands. - **Explanation:** The A-band is the dark band in striated muscle fibers, primarily composed of myosin filaments. The M-line is located in the center of the A-band and serves as an attachment point for the thick filaments (myosin). Thus, this statement is also **true**. ### Step 3: Analyze the Third Statement **Statement:** Thin filaments are firmly attached to the M-line. - **Explanation:** The thin filaments (actin) are not directly attached to the M-line. Instead, they are anchored at the Z-line and extend into the A-band, where they interact with the thick filaments (myosin). Therefore, this statement is **false**. ### Step 4: Analyze the Fourth Statement **Statement:** A sarcomere comprises one full A-band. - **Explanation:** A sarcomere is defined as the functional unit of muscle fibers and includes both the A-band (thick filaments) and the I-band (thin filaments). Therefore, a sarcomere does not consist of only the A-band; it also includes parts of the I-band. This statement is **false**. ### Conclusion From the analysis: - The first statement is true. - The second statement is true. - The third statement is false. - The fourth statement is false. Thus, the correct answer is that the first and second statements about striated muscles are true. ### Final Answer **The correct statements are:** 1. In the center of each I-Band is an elastic fiber (Z-line) which bisects it. 2. M-line is a fibrous membrane in the middle of A bands.
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