A drug that decreases peristalsis would primarily affect which type of muscle?

Peristalsis is the coordinated, wave-like contraction of muscles that occurs in the digestive tract, primarily responsible for moving food through the intestines. This process is primarily driven by smooth muscle, which is found throughout the walls of the gastrointestinal tract. Smooth muscle operates involuntarily, meaning it is not under conscious control, and its contractions are essential for the rhythmic movement of contents through the digestive system.

The other types of muscle listed have different functions that do not relate to peristalsis. Skeletal muscle is responsible for voluntary movements and is under conscious control, while cardiac muscle makes up the heart and is involved in pumping blood, functioning involuntarily but distinctly different from the actions of smooth muscle in the digestive system. Striated muscle is a broader term that includes both skeletal and cardiac muscles, and since it is not specific to peristalsis, it does not pertain to the question asked. Thus, the significant role of smooth muscle in peristalsis justifies why a drug that decreases peristalsis would primarily affect this type of muscle.