In skeletal muscle, the distance between the ends of the thin filaments within a sarcomere is known as which of the following?

• A. A band
• B. H zone
• C. I band
• D. Z disc

Answer: (B)

Verified step by step guidance

1. Understand the structure of a sarcomere, which is the functional unit of skeletal muscle. It is composed of thick filaments (myosin) and thin filaments (actin) arranged in a repeating pattern.
2. Learn the key regions of the sarcomere: the A band (contains the entire length of thick filaments), the I band (contains only thin filaments), the Z disc (marks the boundary between adjacent sarcomeres), and the H zone (the central region of the A band where there are only thick filaments and no overlap with thin filaments).
3. Focus on the H zone, which is the area within the A band where the thin filaments do not extend. This is the region where the distance between the ends of the thin filaments is measured.
4. Compare the definitions of the options provided: A band includes the thick filaments, I band includes only thin filaments, Z disc is the boundary, and H zone is the gap between thin filaments within the A band.
5. Conclude that the correct answer is the H zone, as it specifically refers to the distance between the ends of the thin filaments within the sarcomere.