MCQ
During muscle contraction in humans, the
- Asarcomere does not shorten
- ✓A band remains same
- C$A, H$ and $I$ bands shorten
- Dactin filaments shorten.
✓
Answer
Correct option: B.
A band remains same
b
(b) : According to slidingfilament theory of muscle contraction, the actin and myosin filaments slide past each other with the help of crossbridge to reduce the length of the sarcomeres. The smallest unit of muscle contraction is a sarcomere (which is delineated by $Z$ lines). As a muscle contracts, the $Z$ lines come closer together (shortening sarcomere), the width ofthe $I$ bands decreases, the width of the $H$ zones decreases, but there is no change in the width of the $A$ band. During relaxation, crossbridges disappear and actin filaments slide back from Abands, the width of the $I$ bands and $H$ zones increases, but there is still no change in the width of the A band.
(b) : According to slidingfilament theory of muscle contraction, the actin and myosin filaments slide past each other with the help of crossbridge to reduce the length of the sarcomeres. The smallest unit of muscle contraction is a sarcomere (which is delineated by $Z$ lines). As a muscle contracts, the $Z$ lines come closer together (shortening sarcomere), the width ofthe $I$ bands decreases, the width of the $H$ zones decreases, but there is no change in the width of the $A$ band. During relaxation, crossbridges disappear and actin filaments slide back from Abands, the width of the $I$ bands and $H$ zones increases, but there is still no change in the width of the A band.
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