Ques. 1AIPMT 2001
Which statement is correct for muscle contraction?
- Length of H-zone decreases
- Length of A-band remains constant
- Length of I-band increases
- Length of two Z-line increases
Answer
(1) Length of H-zone decreases, (2) Length of A-band remains constant
Solution
As per NCERT (sliding filament theory), during contraction the thin filaments slide over the thick filaments towards the centre of the A-band.
⇒ The Z-lines are pulled inwards, so the sarcomere shortens; the I-bands get reduced and the H-zone decreases, while the A-band retains its length.
∴ (1) and (2) are correct; (3) and (4) are wrong.
Answer: (1), (2)