Final answer:
Single-unit muscles are smooth muscles controlled by autonomic nerves and hormones, capable of involuntary movements and sustained contractions.
Step-by-step explanation:
The smooth muscles that act like skeletal muscles but are controlled by autonomic nerves and hormones are known as single-unit muscles. These muscles are involved in movements that are involuntary and are found in the internal organs such as the blood vessels, digestive system, and more. Single-unit smooth muscle tissues contain gap junctions that allow the cells to synchronize depolarization and contractions, so the muscle contracts as a whole unit. These muscles are capable of sustained contractions due to latch-bridge mechanisms that do not require continuous ATP for maintenance.
Smooth muscles that act like skeletal muscles but are controlled by autonomic nerves and hormones are multiunit muscles. Multiunit smooth muscles do not possess gap junctions, and contraction does not spread from one cell to the next. They are found in structures like the walls of blood vessels, the iris of the eye, and the arrector pili muscles in the skin.