ABSTRACT

Although skeletal muscle comprises the bulk of muscle tissue in the body,

smooth muscle

is far more important in terms of homeostasis. Most smooth muscle is found in the walls of tubes and hollow organs. Contraction and relaxation of the smooth muscle in these tissues regulates the movement of substances within them. For example, contraction of the smooth muscle in the wall of a blood vessel narrows the diameter of the vessel and leads to a decrease in the flow of blood through it. Contraction of the smooth muscle in the wall of the stomach exerts pressure on its contents and pushes these substances forward into the small intestine. Smooth muscle functions at a subconscious level and is

involuntary

. It is innervated by the

autonomic nervous system

, which regulates its activity.