As the skeletal muscles are of voluntary nature, their contraction requires a nervous stimulation. For this each muscle fibre is individually innervated by a nerve cell. The junction of nerve and muscle cell is known as ‘Motor end plate’. At motor end plate, neurotransmitter acetyl choline is released from nerve ending which stimulates sarcolemma. Sarcolemma then shows electrical depolarization that causes release of calcium ions from sarcoplastic reticulum and thus activation of myosin ATPase enzyme. This enzyme in sarcomeres splits ATP molecules and energy is released. The released energy helps in mechanical sliding of actin and myosin molecules over each other in boat and oar manner, resulting in shortening of sarcomeres length and contraction of muscle fibre and thus whole muscle. As the muscles are attached to bones, the movement of joints occurs and thus body movements.
Apart from providing body movements, the muscle also plays an important role in thermoregulation. Because of heavy mass, the muscle cell metabolism provides basal heat (basal metabolism) to the body even when they are not undergoing contraction (i.e. resting state). With the help of this heat the body temperature is maintained near normal. Paralysis of muscles during diseases leads to hypothermia (i.e. lower body temperature).
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