Final answer:
The third cranial nerve, the oculomotor nerve, is predominantly a motor nerve that controls eye movements, pupil constriction, and eyelid opening. Tests for this nerve check eye movements and pupillary response, which are part of the cranial nerve exam.
Step-by-step explanation:
Cranial Nerve III: Motor or Sensory?
The third cranial nerve, also known as the oculomotor nerve, is primarily a motor nerve. It is responsible for controlling most of the eye movements, the constriction of the pupil, and maintaining an open eyelid. A common test for the oculomotor nerve includes assessing the movements of the eye and the pupillary response to light. The cranial nerve exam evaluates the function of the oculomotor nerve along with the other cranial nerves to provide insights into potential damage to brainstem structures and forebrain areas. For assessing sensory nerves like the olfactory, optic, and vestibulocochlear nerves, which are dedicated to smell, vision, equilibrium, and hearing respectively, different tests are conducted that check the specific senses each nerve is responsible for.