MUSCLE PHYSIOLOGY

Detailed explanation-1: -The Sarcomere. A sarcomere is defined as the region of a myofibril contained between two cytoskeletal structures called Z-discs (also called Z-lines or Z-bands), and the striated appearance of skeletal muscle fibers is due to the arrangement of the thick and thin myofilaments within each sarcomere (Figure 10.2.

Detailed explanation-2: –The dark band is known as ‘A’ or Anisotropic band which carries Myosin whereas the light bands which carry actin and are called I-band or Isotropic band. Hence called striped muscles thanks to the presence of striations.-Hence Myofibrils show dark and lightweight bands in Cardiac muscles and striated muscles.

Detailed explanation-3: -The striated appearance of skeletal muscle tissue is a result of repeating bands of the proteins actin and myosin that are present along the length of myofibrils. Dark A bands and light I bands repeat along myofibrils, and the alignment of myofibrils in the cell causes the entire cell to appear striated or banded.

Detailed explanation-4: -The arrangement of the thick myosin filaments across the myofibrils and the cell causes them to refract light and produce a dark band known as the A Band. In between the A bands is a light area where there are no thick myofilaments, only thin actin filaments. These are called the I Bands.