ANATOMY

Detailed explanation-1: -The myosin and actin filaments overlap in peripheral regions of the A band, whereas a middle region (called the H zone) contains only myosin. The actin filaments are attached at their plus ends to the Z disc, which includes the crosslinking protein -actinin.

Detailed explanation-2: -A-band contains both actin and myosin. M-line and Z-line are in the middle of thick and thin filaments, respectively.

Detailed explanation-3: -The A band contains thick filaments of myosin, which suggested that the myosin filaments remained central and constant in length while other regions of the sarcomere shortened.

Detailed explanation-4: -In physiology, isotropic bands (better known as I bands) are the lighter bands of skeletal muscle cells (a.k.a. muscle fibers). Isotropic bands contain only actin-containing thin filaments. The darker bands are called anisotropic bands (A bands).