During muscle contraction in humans, the:
Correct answer: B. A band remains same
- A. Sarcomere does not shorten
- B. A band remains same
- C. A, I bands and H-zone shorten
- D. Actin filaments shorten.
Explanation
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 Zlines). As a muscle contracts, the Z lines come closer together (shortening sarcomere), the width of the I bands decreases, H -zone disappears ,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. A. Sarcomere does shorten. During contraction about 35% of sarcomere reduces in length. C. I bands shorten , H zone disappears but A bands donot change in length. D. Actin and myosin slide past each other but donot reduce.
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About Support and Movement
Support and movement covers the axial and appendicular skeleton, bone structure, joints and the arrangement of skeletal muscles. Muscle contraction is explained through actin, myosin, sliding filaments, calcium ions and ATP, while arthritis is distinguished as a disorder of joints rather than a normal part of movement.
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