Final answer:
The glossopharyngeal nerve is responsible for innervating the posterior one-third of the tongue and conveying the sense of taste from that region to the brain.
Step-by-step explanation:
The nerve that innervates the posterior one-third of the tongue and is responsible for the sense of taste in that area is the glossopharyngeal nerve. This nerve connects the taste buds in the posterior two thirds of the tongue, which includes the posterior one-third, to the brain. In addition to taste, the glossopharyngeal nerve carries information regarding general sensations from the pharyngeal walls, contributes to the salivation process, and is involved in the gag reflex, which is mediated by both the glossopharyngeal and vague nerves. When gustatory cells are activated by taste molecules, they trigger these nerves to send the taste information to the brain, with the solitary nucleus in the medulla oblongata serving as a primary relay point for the sensory information.