Explain sliding filament theory of muscl | Class 11 Biology Chapter Locomotion and Movement, Locomotion and Movement NCERT Solutions

The sliding filament theory states that contraction of muscle fibre occurs through the sliding of thin filaments over the thick filaments. Actin is a thin filament and myosin is the thick filament. A – bands are the anisotrophic bands of the sarcomere. A- bands appears as dark bands under the microscope. I- bands are the isotropic bands of sarcomere. I- bands appears as light bands under the microscope. Light and dark bands has contractile protein actin and myosin. A Z line elastic fibre is present in the fibre which is attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e. contraction. The I- band contains only thin filaments and also shortens. The A- band does not shorten, it remains the same length but A bands of different sarcomere move closer together during contraction.

The above diagram shows the contraction of muscles fibres according to sliding filament theory by sliding of the thin filaments over thick filaments.