MUSCLE PHYSIOLOGY

Detailed explanation-1: -A sarcomere is defined as the distance between the Z-lines. The Z-lines are pulled closer together during contraction and move further apart during relaxation. The Z-lines are closer during contraction because actin and myosin interaction generates cross-bridges, which slide the myofilaments over each other.

Detailed explanation-2: -– Z-lines define the boundaries of each sarcomere. – The M-line runs down the center of the sarcomere, through the middle of the myosin filaments. – The I-band is the region containing only thin filaments. – The H-zone contains only thick filaments.

Detailed explanation-3: -Two successive Z lines mark the boundary of each sarcomere. The A bands, labeled here with the letter Z, are the regions of the sarcomere that do contain the thicker, darker myosin filaments. And so they are sometimes called the dark bands.