Which of the Following Observations Confirms the Sliding Filament Mechanism

Question

Which of the following observations confirms the sliding filament mechanism for muscle contraction?
A) As the sarcomere shortens, the H zone becomes smaller.
B) As the sarcomere shortens, the width of the A band remains the same.
C) As the sarcomere shortens, the I band becomes smaller.
D) Two of these.
E) All of these.

Accepted Answer

All of these observations confirm the sliding filament mechanism for muscle contraction. The H zone and I band both become smaller as the sarcomere shortens, indicating that the actin filaments are sliding towards the center of the sarcomere, past the myosin filaments. The width of the A band remaining the same suggests that the length of the myosin filaments does not change, which is consistent with the sliding filament theory.