The muscular system is the body's network of tissues for both conscious and unconscious movement. Movement is generated through the contraction and relaxation of specific muscles. Some muscles, like those in the arms and legs, are involved in voluntary movements such as raising a hand or flexing the foot. Other muscles are involuntary and function without conscious effort. Voluntary muscles include skeletal muscles and total about 650 in the whole human body. Skeletal muscles are controlled by the somatic nervous system; whereas the autonomic nervous system controls involuntary muscles. Involuntary muscles include muscles that line internal organs. These smooth muscles are called visceral muscles, and they perform tasks not generally associated with voluntary activity throughout the body even when it is asleep. Smooth muscles control several automatic physiological responses such as pupil constriction when iris muscles contract in bright light and blood vessel dilation when smooth muscles...