Concept:Geometric changes in the sarcomere during sliding.
Formula:N/A (Conceptual)
Solution:- During the power stroke, thick myosin filaments act like ratchets, dragging the thin actin filaments inward toward the M-line.
- Because the thin filaments are physically anchored to the Z-lines, pulling them inward forces the two Z-lines to move closer together, shortening the entire sarcomere.
- Simultaneously, the region containing only isolated thin filaments (the I-band) is pulled into the overlap zone, causing it to visually shorten and nearly disappear.
Why other options are incorrect:Z-lines never move further apart (distant/enlarged) during an active concentric contraction. The I-band physically must shorten as it slides into the A-band.
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