MUSCLE PHYSIOLOGY

Detailed explanation-1: -Sarcomere ends, called Z-lines, are marked by electron-dense structures that serve as anchor sites for actin-based thin filaments, while the sarcomere center, or M-line, is characterized by a similar anchoring structure for bipolar myosin-based thick filaments (Figure 1).

Detailed explanation-2: -Thin filaments attach to a protein in the Z disc called alpha-actinin and occur across the entire length of the I band and partway into the A band.

Detailed explanation-3: -In electron micrographs of cross-striated muscle, the Z-line (from the German “zwischen” meaning between) appears in between the I-bands as a dark line that anchors the actin myofilaments.

Detailed explanation-4: -“Sarcomeres are mainly made up of actin and myosin protein strands called filaments. Muscle shortening or contraction depends on these filaments sliding against each other, and requires that the actin filaments are anchored in planes, called Z-discs.