Final answer:
The trochlear nerve is classified as a motor cranial nerve, involved in eye movement by controlling the superior oblique muscle. It is neither sensory nor mixed and is unrelated to the gustatory system.
Step-by-step explanation:
The trochlear nerve (cranial nerve IV) is classified by function as a motor nerve. It is responsible for the contraction of the superior oblique muscle, which is one of the extraocular muscles that controls eye movement. No cranial nerves are purely involved with the gustatory system, which is related to taste, although the facial and glossopharyngeal nerves have roles in taste sensation as part of their mixed sensory and motor functions.
Specifically, the trochlear nerve is among the three cranial nerves (oculomotor, trochlear, and abducens) that are strictly motor and each controls different extraocular muscles to coordinate eye movements. These motor nerves do not carry sensory fibers or contribute to the gustatory system.