Final answer:
The 9th cranial nerve, known as the glossopharyngeal nerve, is a mixed nerve with both motor and sensory functions related to swallowing, salivation, and taste. The cranial nerve exam assesses the functioning of this nerve through tests like the gag reflex and taste assessment on the posterior part of the tongue.
Step-by-step explanation:
The 9th Cranial Nerve - Glossopharyngeal Nerve
The 9th cranial nerve is known as the glossopharyngeal nerve. It is a mixed nerve that carries both motor and sensory fibers. This nerve is responsible for a variety of functions, including the motor control necessary for swallowing and salivation, as well as the sensory function associated with taste on the posterior third of the tongue. To test this nerve, a clinician may assess the gag reflex, the ability to swallow, and the sense of taste at the back of the tongue.
The cranial nerve exam is an essential part of a neurological assessment that evaluates the functions controlled by the cranial nerves, including special and general senses of the head and neck, and the movement of various muscles. This includes examining structures involved in the autonomic control of pupillary size, salivation, and the regulation of visceral functions in the thoracic and abdominal cavities.
Sensory cranial nerves, such as the olfactory (I), optic (II), and vestibulocochlear (VIII) nerves, are primarily dedicated to special senses like smell, vision, and hearing. The glossopharyngeal nerve (IX), along with the facial nerve, relays taste sensations to the brainstem. Moreover, the trigeminal (V) nerve transmits the general somatic senses from the head akin to spinal nerves carrying sensations from the rest of the body.