The glossopharyngeal nerve is the ninth cranial nerve, primarily responsible for sensory and motor functions in the throat. It plays a key role in taste sensation from the posterior one-third of the tongue and helps regulate swallowing by controlling muscles in the pharynx. Additionally, the glossopharyngeal nerve contributes to the autonomic nervous system by influencing salivary gland secretion, particularly from the parotid gland. It also carries sensory information related to blood pressure and oxygen levels from the carotid body and sinus, aiding in cardiovascular regulation.