Read the following statements regarding the events occurring during the maximal contraction of a skeletal muscle: (A) The Z-lines attached to the actins are pulled inwards. (B) The I-bands get reduced. (C) The A-bands retain their length. (D) The H-zone disappears. How many of the above statements are correct?

Step-by-step solution

According to the sliding filament theory, during muscle contraction, the thin (actin) filaments slide over the thick (myosin) filaments. This pulls the Z-lines attached to the actins inwards, causing a shortening of the sarcomere. As the thin filaments slide inwards, the I-bands get reduced. The thick filaments do not change their length, so the A-bands retain their length. During maximal contraction, the thin filaments from opposite ends of the sarcomere overlap each other in the centre, causing the H-zone to disa