Final answer:
The tenth cranial nerve, the vagus nerve, is a combination of motor and sensory functions. Cranial nerve exams help test the nerve's control over sensory and motor functions, highlighting potential damage or deficits in brainstem function.
Step-by-step explanation:
The tenth cranial nerve, also known as the vagus nerve (cranial nerve X), is both a motor and sensory nerve. It is responsible for autonomic functions in the thoracic and superior abdominal cavities, including heart rate, digestion, and respiratory rate. Almost solely motor cranial nerves, like the oculomotor nerve, control eyelid movement and some eye movements, while others, such as the glossopharyngeal nerve, have mixed sensory (like taste) and motor functions (such as swallowing).
To test the vagus nerve, a clinician may observe the palate when a person says "ahh" or perform a gag reflex test. Sensory cranial nerves like the olfactory (I), optic (II), and vestibulocochlear (VIII) nerves are primarily concerned with smell, vision, and hearing, respectively. Cranial nerve exams are pursuits to assess damage or deficits in brainstem function that control these various functions.