Question

When Skeletal muscle contracts an arrangement of the alternating light and dark bands traversing each skeletal muscle cell changes. Which of the following statements is not correct?(a) The dark A bands will remain a constant length(b) The space occupied by the H zone will not change(c) The light I bands will shorten(d) The z lines come closer together(e) The I band consists solely of thin actin filaments

Answer 1

Answer:

(b) The space occupied by the H zone will not change

Explanation:

• The sarcomere is the contractile unit in a skeletal muscle.

• Thick myosin myofilaments are located in the central region of the sarcomere, which corresponds to the A band.

• Thin filaments united to the Z lines, extends to the interior of the A band until they reach the border of the H band.

• I band is formed solely of thin actin filaments, belonging to two sarcomeres adjacent to a Z line. (option (e) is correct)

• When the muscle contracts, the muscular fiber gets shorter and thicker due to the reduction in length of the sarcomere. The H line and the I band get shorter (Option (b) is not correct, but option (c) is correct). The Z lines get closer to the A band, meaning that they get closer to each other (Option (d) is correct). A band keeps constant in length (Option (a) is correct)

• This change is produced by movement mechanisms that involve a change in the relative position of actin and myosin filaments.