Final answer:
The trochlear nerve (cranial nerve IV) is classified as a motor nerve, responsible for controlling the superior oblique muscle of the eye.
Step-by-step explanation:
The trochlear nerve (cranial nerve IV) is classified according to function as a motor nerve. This cranial nerve is specifically responsible for controlling the superior oblique muscle of the eye, which is one of the extraocular muscles involved in rotatory eye movements. It is one of the three cranial nerves that control eye movement; the others being the oculomotor (CNIII) and abducens (CNVI) nerves. As a motor nerve, the trochlear nerve conveys motor signals from the brain to muscles to create movement, in contrast to sensory nerves that transmit sensory information from the body to the brain.