Gustatory system including taste buds, cranial nerves, and primary gustatory areas.

Gustatory system including taste buds, cranial nerves, and primary gustatory areas.

• A. Taste buds on the tongue and other areas are innervated by CN VII (anterior 2/3), CN IX (posterior 1/3), and CN X (vallate and epiglottis). Taste signals ascend to the nucleus of the solitary tract, project to the thalamus (ventral posteromedial nucleus), and reach the gustatory cortex (insula and frontal operculum).
• B. Taste buds innervated by CN III, IX, and XII; signals to spinal cord.
• C. Taste buds innervated by CN V only; signals to cerebellum.
• D. Taste buds innervated by CN VII and IX only; signals bypass thalamus to cortex.

Answer: (A)

Taste information starts at taste buds scattered on the tongue and in other areas, and is carried by three cranial nerves depending on the region. The anterior two-thirds of the tongue send taste signals via the chorda tympani branch of the facial nerve; the posterior one-third via the glossopharyngeal nerve; and taste from the vallate papillae and the epiglottis via the vagus nerve. These afferent signals first reach the nucleus of the solitary tract in the medulla. From there, second-order neurons project to the ventral posteromedial nucleus of the thalamus, and finally the information arrives at the primary gustatory cortex, located in the insula and frontal operculum. This pathway explains why the listed nerves and brain regions are involved in taste. Choices that assign other nerves (such as III, XII, or V) or propose signals going to the spinal cord or cerebellum, or bypassing the thalamus, don’t fit the known gustatory route.

Taste information starts at taste buds scattered on the tongue and in other areas, and is carried by three cranial nerves depending on the region. The anterior two-thirds of the tongue send taste signals via the chorda tympani branch of the facial nerve; the posterior one-third via the glossopharyngeal nerve; and taste from the vallate papillae and the epiglottis via the vagus nerve. These afferent signals first reach the nucleus of the solitary tract in the medulla. From there, second-order neurons project to the ventral posteromedial nucleus of the thalamus, and finally the information arrives at the primary gustatory cortex, located in the insula and frontal operculum. This pathway explains why the listed nerves and brain regions are involved in taste.

Choices that assign other nerves (such as III, XII, or V) or propose signals going to the spinal cord or cerebellum, or bypassing the thalamus, don’t fit the known gustatory route.