ABSTRACT
Skeletal muscle cells are of mesodermal origin. Many muscle fibres grouped together are termed fascicles. The major contractile proteins in skeletal muscle are actin and myosin. Actin is a globular protein that is a chief constituent of the thin filaments of the sarcomere. Myosin molecules have six distinct subunits: two heavy chains and four light chains. Surrounding each myofibril is an intracytoplasmic membranous sac called the sarcoplasmic reticulum. Voltage-sensitive membrane proteins in the T-tubule, known as modified dihydropyridinereceptors, are mechanically coupled with ryanodine receptors of the sarcoplasmic reticulum. The myotendinous junction is the area where insertion of every skeletal muscle fibre into its tendon occurs. Control of muscle contraction is by recruitment of motor units. Muscle cell damage by, for example, physical trauma leads to release of inflammatory mediators and damaged cellular components. Electromyography (EMG) is the recording of electrical activity in skeletal muscle.
