Which of the following best describes smooth muscle?

Smooth muscle is best characterized as being nonstriated and involuntary. This type of muscle is found in the walls of hollow organs, such as the intestines, blood vessels, and the bladder, where it plays a crucial role in regulating processes like digestion and blood flow.

The term "nonstriated" refers to the absence of the banding pattern seen in skeletal muscle, which is composed of striated fibers. Instead, smooth muscle fibers have a smooth appearance and are typically spindle-shaped. The "involuntary" aspect indicates that smooth muscle operates without conscious control, meaning that its contractions are regulated by the autonomic nervous system and hormones rather than through voluntary actions.

Understanding the distinguishing features of smooth muscle helps to clarify its functional roles in the body compared to skeletal and cardiac muscle, which are striated and have varying levels of voluntary control.