Question: 151: According to the sliding filament theory:
(1) Actin and myosin filaments slide over each other to increase the length of the sarcomere.
(2) Length of A-band does not change.
(3) I-band increases in length
(4) The actin filaments slide away from A-band resulting in shortening of sarcomere.
Answer: Option (2)
Explanation:
According to the sliding filament theory, muscle contraction occurs due to sliding of actin filaments over myosin filaments without any change in their individual lengths.
The A-band represents the length of the myosin filament. Since myosin filaments do not shorten or lengthen during contraction, the length of the A-band remains constant.
During contraction, actin filaments slide towards the center of the sarcomere, causing shortening of the sarcomere.
As a result, the I-band decreases in length and the H-zone may disappear, but the A-band remains unchanged.
Therefore, the correct statement according to the sliding filament theory is that the length of the A-band does not change.