What primary functions are associated with the glossopharyngeal nerve?

The glossopharyngeal nerve, also known as cranial nerve IX, is primarily responsible for several functions that are crucial for both taste and the mechanics of swallowing. It plays a vital role in the sensation of taste from the posterior one-third of the tongue. Additionally, this nerve is involved in the act of swallowing, as it innervates muscles in the pharynx, which are essential for this function. The gag reflex, an important protective mechanism, is also facilitated by the glossopharyngeal nerve, as it contributes to the sensation that triggers this reflex.

By understanding these specific roles of the glossopharyngeal nerve, it becomes clear why taste, swallowing, and gag reflex are accurately associated with its primary functions. The other options do not accurately represent the functions of the glossopharyngeal nerve, focusing instead on different cranial nerves or functions that are not its responsibility.