Final answer:
The statement is true; single-unit smooth muscle, found in the walls of hollow organs, contracts rhythmically as a coordinated unit through connections made by gap junctions.
Step-by-step explanation:
The statement that single unit smooth muscle contracts rhythmically as a unit is true. Single-unit smooth muscle, also known as visceral muscle, is made up of fibers that are connected by gap junctions. These junctions allow the muscle to contract in a coordinated and rhythmic manner, acting as a unit.
This type of smooth muscle is present in the walls of hollow organs such as the stomach and urinary bladder, and it is essential for processes like peristalsis, which moves substances through the body. Rather than being controlled by direct neural stimulation alone, single-unit smooth muscles can also be stimulated by the autonomic nervous system, by hormones, or can contract spontaneously or in response to stretching.