Question

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

• A. Length of actin filaments
• B. Size of region enclosed by two Z lines
• C. H zone
• D. I band

Answer 1

The correct option is A Length of actin filaments

Sarcomeres are composed of long, fibrous proteins as filaments that slide past each other when a muscle contractor relaxes. Two of the important proteins are myosin, which forms the thick filament, and actin, which forms the thin filament. Upon muscle contraction, the A-bands do not change their length (1.85 micrometers in mammalian skeletal muscle), whereas the I-bands and the H-zone shorten. This causes the Z lines to come closer together.

So the correct option is 'Length of actin filament'.