What is the primary function of smooth muscle?

The primary function of smooth muscle is to control involuntary organ contractions. Smooth muscle is a type of non-striated muscle that is found in the walls of internal organs such as the gastrointestinal tract, blood vessels, bladder, and respiratory passages. Unlike skeletal muscle, which is responsible for voluntary movements, smooth muscle operates automatically, responding to signals from the autonomic nervous system and hormones. This allows smooth muscle to regulate functions such as the movement of food through the digestive tract, the constriction and dilation of blood vessels, and the contraction of the bladder during urination, illustrating its essential role in maintaining vital bodily functions without conscious control.

The other choices reflect functions associated with different types of muscle. Cardiac muscle, for example, is responsible for contracting the heart, while skeletal muscle is involved in voluntary movements and supporting skeletal activity.