The H-zone in the skeletal muscle fibre is due to

Question

Draw the diagram of a sarcomere of skeletal muscle showing different regions.

Answer 1

The question asks about the specific region within the skeletal muscle fiber known as the H-zone. To understand the H-zone, it is important to review the structure of the sarcomere, which is the functional unit of a muscle fiber.

The sarcomere consists of different bands and zones:

The A-band spans the length of the thick (myosin) filaments and is responsible for the dark band of the striated muscle appearance.
The I-band contains only thin (actin) filaments and appears as the light band.
The H-zone is the central region of the A-band where there are no overlapping actin filaments.

Let's analyze the options:

Option 1: "The absence of myofibrils in the central portion of A-band" – This is incorrect because myofibrils are still present, and this option misinterprets what constitutes the H-zone.
Option 2: "The central gap between myosin filaments in the A-band" – This is incorrect because myosin filaments extend throughout the A-band, including the H-zone.
Option 3: "The central gap between actin filaments extending through myosin filaments in the A-band" – This is correct. The H-zone is characterized by the absence of actin filaments in this central region, thus creating a gap.
Option 4: "Extension of myosin filaments in the central portion of the A-band" – This is incorrect because the myosin filaments span the entire A-band, not extending specifically in the H-zone.

Thus, the correct answer is the central gap between actin filaments extending through myosin filaments in the A-band, which corresponds to Option 3.

In conclusion, the key feature of the H-zone is its location within the A-band, where only myosin filaments are present, creating a central gap without actin filaments.

Answer 2

The question asks about the specific region within the skeletal muscle fiber known as the H-zone. To understand the H-zone, it is important to review the structure of the sarcomere, which is the functional unit of a muscle fiber.

The sarcomere consists of different bands and zones:

The A-band spans the length of the thick (myosin) filaments and is responsible for the dark band of the striated muscle appearance.
The I-band contains only thin (actin) filaments and appears as the light band.
The H-zone is the central region of the A-band where there are no overlapping actin filaments.

Let's analyze the options:

Option 1: "The absence of myofibrils in the central portion of A-band" – This is incorrect because myofibrils are still present, and this option misinterprets what constitutes the H-zone.
Option 2: "The central gap between myosin filaments in the A-band" – This is incorrect because myosin filaments extend throughout the A-band, including the H-zone.
Option 3: "The central gap between actin filaments extending through myosin filaments in the A-band" – This is correct. The H-zone is characterized by the absence of actin filaments in this central region, thus creating a gap.
Option 4: "Extension of myosin filaments in the central portion of the A-band" – This is incorrect because the myosin filaments span the entire A-band, not extending specifically in the H-zone.

Thus, the correct answer is the central gap between actin filaments extending through myosin filaments in the A-band, which corresponds to Option 3.

In conclusion, the key feature of the H-zone is its location within the A-band, where only myosin filaments are present, creating a central gap without actin filaments.

The H-zone in the skeletal muscle fibre is due to

The Correct Option is C

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