Muscle contraction

 

In a contracted striated muscle, the A and I bands completely disappear giving room for the contraction band made up of the actin and myosin filaments.   Also in the contracted muscle, the sarcomeres shortens leading to the shortening of the distance between the 2 discs.   The actin filaments become almost completely approximated.   This leads to the shortening of the length of the muscle fiber and the whole of the muscle itself.   The mechanism is explained by the sliding filament theory of muscle contraction.