Which statement best describes the sliding filament model of a sarcomere contraction?

• A. The A band and the H zone both become smaller.
• B. The I bands gets smaller but the H zone remains the same.
• C. The I bands gets smaller while the A band gets larger.
• D. The I bands and H zone get smaller while the A band remains the same size.

Answer: (D)

Verified step by step guidance

1. Understand the structure of a sarcomere: A sarcomere is the basic unit of a muscle's striated muscle tissue. It is composed of thick filaments (myosin) and thin filaments (actin). Key regions include the A band, I band, and H zone.
2. Identify the components involved in contraction: During muscle contraction, the actin and myosin filaments slide past each other, which leads to changes in the sarcomere's structure.
3. Analyze the changes in the sarcomere during contraction: The sliding filament model explains that the I bands and H zone decrease in size as the actin filaments slide over the myosin filaments. The A band, which corresponds to the length of the myosin filaments, remains unchanged.
4. Evaluate the options given: Compare each statement with the sliding filament model. The correct description should reflect the changes in the I bands and H zone while noting that the A band remains constant.
5. Select the correct statement: Based on the sliding filament model, the correct statement is that the I bands and H zone get smaller while the A band remains the same size.