GENERAL HISTOLOGY

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: -Each myofibril consists of a series of contractile units (sarcomeres) connected at a protein border (the Z line). Thin filaments(actin) of adjacent sarcomeres are present in the Z line between the thin filaments are thick filaments(myosin).