Structure of Skeletal Muscle Fiber - Guyton Notes
Muscle Fiber Muscle fibers range from 10 to 80 micrometers . Most fibers run the full length of muscle. About 98% are innervated by one nerve ending. Nerve endings are usually near the fiber middle. Sarcolemma : The sarcolemma encloses each skeletal muscle fiber. It consists of a plasma membrane and polysaccharide coat . The outer coat contains collagen fibrils. Sarcolemma fuses with tendon fibers at each end. Tendon fibers form bundles that attach to bone. Filaments and Myofibrils: Each fiber contains hundreds to thousands of myofibrils. Each myofibril has about 1,500 thick myosin filaments. Each myofibril has about 3,000 thin actin filaments. Actin and myosin proteins drive muscle contraction. Sarcomere and Z discs: Actin filament ends attach to the Z disc. Z discs connect adjacent myofibrils across the fiber. Filament alignment gives skeletal muscle its striated appearance. A sarcomere lies between two successive Z discs. The contracted sarcomere length is about 2 micro...