The glossopharyngeal nerve (CN IX) is responsible for sensations in which areas?

The glossopharyngeal nerve (CN IX) is primarily responsible for sensations from the posterior part of the tongue and the pharynx, including taste. This cranial nerve plays a crucial role in the sensory function by innervating taste buds located on the posterior one-third of the tongue and contributing to the sensation of touch and temperature in that area. Additionally, it provides sensory innervation to the pharynx, which is essential for the gag reflex and swallowing.

The second aspect of its function involves the baroreceptor and chemoreceptor inputs from the carotid body and sinus, which are crucial for monitoring blood pressure and gas levels. The other options do not accurately represent the specific areas serviced by the glossopharyngeal nerve. For instance, taste from the anterior tongue is associated with the facial nerve (CN VII), and mouth sensations and taste involve contributions from multiple nerves including the facial nerve and the trigeminal nerve (CN V). Thus, the correct choice highlights the specific area of the posterior tongue and pharynx that is innervated by the glossopharyngeal nerve, making it the most accurate answer.