Smaknervenes

Smaknervenes, or the taste nerves, are the cranial nerves responsible for conveying gustatory information from taste receptor cells to the brain. In humans, the principal contributors are the facial nerve (cranial nerve VII), the glossopharyngeal nerve (cranial nerve IX), and the vagus nerve (cranial nerve X). Taste signals from the anterior two-thirds of the tongue travel via the chorda tympani, a branch of CN VII; those from the posterior one-third travel via CN IX; and taste from the epiglottis and lower pharynx is carried by CN X.

Taste buds are located on the tongue's circumvallate and fungiform papillae, as well as in the epiglottis and some pharyngeal regions. The chorda tympani carries taste fibers from the anterior tongue, while the lingual nerve (a branch of CN V for general sensation) transmits somatic sensation but not taste from the same area. The distinct pathways for taste ensure that different regions of the tongue can convey gustatory information to the brain.

The pathway for taste begins with the first-order neurons in the respective sensory ganglia—geniculate (VII), petrosal or inferior (IX), and nodose (X)—which send information to the nucleus of the solitary tract in the medulla. From there, signals ascend to the ventral posterior medial nucleus of the thalamus and are finally projected to the gustatory cortex in the insula and frontal operculum.

Clinical notes include ageusia (loss of taste) and dysgeusia (distorted taste), which can result from injury or disease affecting these nerves. Taste perception often declines with age and can be influenced by illness, medications, and olfactory function.

See also: gustation, taste buds, insular cortex.