Final answer:
Single-unit smooth muscle contracts as a single unit due to gap junctions, while multiunit smooth muscle contraction is confined to the stimulated cell. Single-unit smooth muscle is found in most visceral organs and has a stress-relaxation response, while multiunit smooth muscle is found around blood vessels, respiratory airways, and eyes.
Step-by-step explanation:
Single-unit smooth muscle is a type of smooth muscle that contracts as a single unit due to the presence of gap junctions. This type of muscle is found in the walls of most visceral organs except the heart, and it is often referred to as visceral muscle. It has a stress-relaxation response that allows it to stretch, contract, and relax to accommodate the expansion and contraction of the organ.
Multiunit smooth muscle, on the other hand, does not have gap junctions and contraction is confined to the cell that was originally stimulated. This type of muscle is found around large blood vessels, in the respiratory airways, and in the eyes. It is stimulated by autonomic nerves or hormones, but not by stretching.