Skeletal muscles shorten and pull on bones to cause movement of body parts. Each muscle has three major parts. In addition, a muscle has two or more points of attachment to bones. The more fixed point of attachment is called the origin , and the point of attachment to the bone that moves when the muscle contracts is called the insertion. Tendons are fibrous bands of connective tissue that bind muscles to bones at their origin and insertion.
Tendons vary in length.
A wide, thin, sheetlike tendon is referred to as an aponeurosis. For a skeletal muscle to contract, it must be stimulated by a nervous impulse. The muscle receives this impulse from a motor nerve . One motor nerve may stimulate a few or many muscle fibers within a muscle. The nerve and muscle fibers work together as a motor unit .