The bulk of muscle tissue in the body is comprised of striated muscle fibers, which are mostly attached to the skeleton. All muscle fibers are comprised of excitable tissue that can be stimulated mechanically, chemically, or electrically. The two other types of muscle (cardiac and smooth) are comprised of specialized tissues that initiate contractions without requiring stimulation from other sources. Skeletal muscle, however, must receive stimulation from the nervous system in order to contract and is supplied which abundant nervous tissues. Because most skeletal muscle movement is under conscious control, it is also commonly referred to as voluntary muscle.