During muscle contraction in humans, the
- sarcomere does not shorten
- A band remains same
- A, H and I bands shorten
- actin filaments shorten.
Answer
(2) A band remains same
Solution
As per NCERT (sliding filament theory), contraction of a muscle fibre takes place by the sliding of the thin (actin) filaments over the thick (myosin) filaments.
⇒ The Z-lines attached to the actin filaments are pulled inwards, so the sarcomere shortens.
⇒ The I-bands get reduced (and the H-zone narrows), whereas the A-bands retain their length.
⇒ The actin and myosin filaments themselves do not shorten; they only slide past each other.
∴ During muscle contraction, the A band remains the same.
Answer: (2)