Glossopharyngeal

The abdominal vagus and sympathetic nerves are the most important afferent inputs involved in vomiting induced by chemotherapy and radiation [31]. The input from vestibular nerves and the cerebellum plays an important role in the motion disease [52]. The afferent inputs from vagal, trigeminal and glossopharyngeal nerves terminate eventually in the nucleus solitarius tract located in the medulla oblongata which has neuronal connections with other medullary areas involved in emesis, for example, area postrema [53]. 

Because of sensory neuropathy, deep pain is often experienced by patients given vincristine. Through involvement of the glossopharyngeal nerve, throat pain may occur, as may deep pain of almost any other area of the body (31,32). Neuropathic changes are not always peripheral. Hallucinations and overall mental status changes, such as depression and/or psychosis, are also rarely reported (31,32). Another CNS effect is the syndrome of inappropriate antidiuretic hormone secretion, which is a well-characterized side effect of vincristine (31,32). 

By contrast, bony fish have their olfactory organs on the dorsal side of the snout at some distance from the mouth. The olfactory system in fish involves the first (olfactory) cranial nerve, while the ninth (glossopharyngeal) and other nerves serve the sense of taste. 

Not surprisingly, much research in sharks, skates and rays has focused on the responses of sharks to human body odors. Human blood attracts sharks, while sweat does not, and urine was even slightly repellent (Tester, 1963). Practitioners use whale meat and mixtures of fish meal and fish oils as shark attrac-tants. In both carnivorous and herbivorous bony fish (Osteichthyes) smell deals with prey odors, social odors, and chemical stimuli in homing, and it is mediated by the first cranial nerve, the olfactory nerve. By contrast, taste serves in detection and selection of food and avoidance of toxic food, and it employs the facial, glossopharyngeal, vagal, and hypoglossal nerves. 

The metallic sensation arises from stimulation with certain metallic salts, such as silver nitrate, and is also associated with l-octen-3-one (30). Metallic taste sensations may also arise with pathologies of the glossopharyngeal nerve. 

G. Hellekant, V. Danilova, Y. Ninomiya. Primate sense of taste behavioral and single chorda tympani and glossopharyngeal nerve fiber recordings in the rhesus monkey, Macaca mulatto. J Neuropihysial, Tl (2), 978-993, 1997. 

Four cranial nerves subserve the sense of taste, three of these (facial, glossopharyngeal and vagus) innervate taste bud systems (Fig. 1) and one (trigeminal) supplies free nerve ending receptors. Both of these types of receptors respond to chemical stimuli. Only the taste bud systems of the facial and glossopharyngeal nerves have been studied in sufficient detail with many food compounds. 

Figure 1. Diagram of the three cranial nerves and associated sensory ganglia that innervate taste buds. As illustrated, electrical recordings were taken from single neurons in the ganglia. Geniculate ganglion in facial nerve petrosal in glossopharyngeal nodose in vagus.

Geniculate Ganglion (Facial Nerve) GG. Petrosal Ganglion (Glossopharyngeal Nerve) PG... 

Formaker BK, Hill DL. Lack of amiloride sensitivity in SHR and WKY glossopharyngeal taste responses to NaCl. Physiol. Behav. 

Excessive volumes of local anesthetic in a confined space can lead to life-threatening upper airway obstruction. When glossopharyngeal nerve blocks are used for tonsillectomy, children under 15 kg should be given 1 ml or less of 0.25% bupivacaine per tonsil (350). 

Sher MH, Laing Dl, Brands E. Life-threatening upper airway obstruction after glossopharyngeal nerve block possibly due to an inappropriately large dose of bupivacaine Anesth Analg 1998 86(3) 678. 

Taste receptors reside within taste buds on the tongue, the larynx, and the palate. There are four primary taste sensations sour, sweet, bitter, and salty. By mixing these primary taste sensations, the brain can identify many specific tastes (analogous to primary color mixing). Impulses from the taste buds are carried through the facial, glossopharyngeal, and vagus nerves (cranial nerves VII, IX, and X, respectively) to the brain. Taste is modified by the presence of odor, and in the absence of olfactory ability, taste is virtually eliminated. 

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