How is smooth muscle primarily characterized?

Smooth muscle is primarily characterized by its involuntary control. This means that the contractions of smooth muscle are not consciously controlled, unlike skeletal muscle, which is voluntary. Smooth muscle is found in various tissues throughout the body, including the walls of hollow organs such as the intestines, blood vessels, and the bladder.

Involuntary control allows smooth muscle to function automatically, responding to various physiological signals without the need for conscious thought. This is crucial for processes such as digestion and the regulation of blood flow, where continuous, rhythmic contractions are necessary for the body’s functioning.

While smooth muscle does have high endurance due to its ability to sustain contractions over long periods and is found in places where constant tension is required, the defining characteristic that distinguishes it from other muscle types is indeed its involuntary nature.