During muscular contraction which of the following events occur? Choose the correct answer from the options given below.
- B, D, E and A only
- A, C, D and E only
- A, B, C and D only
- B, C, D and E only
Answer
(2) A, C, D and E only
Solution
As per NCERT (sliding filament theory), during contraction the thin (actin) filaments slide over the thick (myosin) filaments towards the centre of the sarcomere.
A: Correct – the H zone disappears as the thin filaments slide into it.
B: Incorrect – the 'A' band retains its length.
C: Correct – the 'I' band gets reduced.
D: Correct – the myosin head hydrolyses ATP; releasing the ADP and Pi it goes back to its relaxed state.
E: Correct – the Z-lines attached to the actins are pulled inwards, shortening the sarcomere.
∴ Correct: A, C, D and E only.
Answer: (2)