Question

upon contraction of sarcomere in skeletal muscle fibres , reduction is not observed in?

1. length of actin filaments

2. size of region enclosed by 2 z lines

3. h zone

4. i band

Answer 1

Upon muscle contraction, the A-bands do not change their length (1.85 micrometer in mammalian skeletal muscle), whereas the I-bands and the H-zone shorten. This causes the Z lines to come closer together. The protein tropomyosin covers the myosin binding sites of the actin molecules in the muscle cell.
so the answer is
1. length of actin filaments