MUSCLE PHYSIOLOGY

Detailed explanation-1: -In conclusion, the correct order of muscle structures is muscle, fascicles, fibers, myofibrils, and sarcomeres, from largest to smallest.

Detailed explanation-2: -The smallest contractile unit of skeletal muscle is the muscle fiber or myofiber, which is a long cylindrical cell that contains many nuclei, mitochondria, and sarcomeres (Figure 1) [58]. Each muscle fiber is surrounded by a thin layer of connective tissue called the endomysium.

Detailed explanation-3: -The smallest unit of muscle contraction is a sarcomere(which is delineated by Z-lines). As a muscle contracts, the Z Lines come closer together (shortening sarcomere), the width of the I bands decreases, the width of the H zones decreases but there is no change in the width of A band.

Detailed explanation-4: -The sarcomere is the smallest functional unit of a skeletal muscle fiber and is a highly organized arrangement of contractile, regulatory, and structural proteins. It is the shortening of these individual sarcomeres that lead to the contraction of individual skeletal muscle fibers (and ultimately the whole muscle).