MUSCLE PHYSIOLOGY

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: -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-3: -A sarcomere is the basic contractile unit of muscle fiber. Each sarcomere is composed of two main protein filaments-actin and myosin-which are the active structures responsible for muscular contraction.

Detailed explanation-4: -Skeletal and cardiac muscles are known as striated muscles, because the filaments of actin and myosin that power their contraction are organized into repeating arrays, called sarcomeres, that have a striated microscopic appearance.