Describe Gustation

Gustation

• sense of taste, detection of tastants

• gustatory cells = chemoreceptors in taste buds

Papillae

• epithelium and CT elevations on tongue

• filiform: short and spiked, no taste buds (no role in gustation), manipulate food, anterior two-thirds of tongue surface

• fungiform: mushroom-shaped, contain few taste buds, tip and sides of tongue

• foliate: leaflike ridges, not well developed, few taste buds in early childhood, posterior lateral tongue

• vallate (circumvallate): largest, least numerous, most of taste buds, in row of 10-12 posterior dorsal tongue surface, inverted V shaped

Gustatory cells

• neuroepithelial chemoreceptive cells of taste buds

• gustatory microvillus (taste hairs) dendritic ending → extend through taste pore (tongue surface)

• tastants (tasty molecules) dissolve in saliva and stimulate microvillus

Gustatory pathways

• sensory neurons connect to multiple gustatory cells in tongue + project to medulla

• CN VII (facial nerve): anterior 2/3 tongue

• CN IX (glossopharyngeal): posterior 1/3

• secondary medullary neurons: to thalamus

• tertiary thalamic neurons: to gustatory cortex in insula

Pathway of Gustatory

1. primary neuron in CN signals to nucleus solitarius in medulla → triggers salivation and stomach secretions → thalmus → primary gustatory cortex for conscious taste

   • nauseating stimuli → trigger gag or vomiting

   • taste integrated with temp, texture and smell (food = less taste if olfaction is blocked i.e. sick/congested)