The Chemical Senses: Gustation (Taste)

Vocabulary flashcards covering gustation anatomy, receptors, transduction, and central processing based on lecture notes.

Gustation

The sense of taste; contact chemosensation on the tongue involving taste buds.

Papillae

Specialised invaginations on the tongue surface that house taste buds.

Fungiform papillae

Front (anterior) tongue papillae with about 3 taste buds each.

Circumvallate papillae

Large papillae at the back of the tongue with deep troughs and ~250 taste buds per papilla.

Folate (foliate) papillae

Parallel ridges on the sides of the tongue containing many taste buds (≈600).

Taste bud

Sensory organ within the tongue that contains taste receptor cells and a taste pore.

Taste receptor cell

Epithelial cells in taste buds that detect tastants via receptors.

Microvilli

Small projections on taste cells that increase surface area and host receptor proteins; extend into the taste pore.

Taste pore

Opening at the surface where tastants contact receptor proteins.

Transduction (gustation)

Process by which tastants are converted into electrical signals in taste cells.

Amiloride-sensitive Na+ channel

Ion channel mediating salt detection; Na+ influx causes depolarisation.

H+-sensitive TRP channel (PKD variant)

Proton-activated channel underlying sour taste; depolarises cells by blocking K+ efflux.

T1R2/T1R3

G-protein-coupled receptor heterodimer for sweet taste.

T1R1/T1R3

GPCR heterodimer for umami taste.

T2R

Family of GPCR bitter taste receptors with multiple subtypes.

Umami

Meaty taste elicited by glutamate; detected by T1R1/T1R3 and MSG.

Sweet

Taste elicited by sugars; detected by T1R2/T1R3.

Bitter

Taste detected by T2R receptors; diverse ligands and subtypes.

Salt and sour transduction

Salt: amiloride-sensitive Na+ channel depolarises the cell; Sour: H+-sensitive channels/TRP depolarise via K+ block and Ca2+ influx.

PLCβ2

Phospholipase C beta-2; key enzyme in GPCR-mediated taste signaling.

IP3

Inositol trisphosphate; second messenger that mobilises Ca2+ in taste cells.

TRPM5

Transient receptor potential channel essential for depolarisation and transmitter release in taste cells.

Basal cells

Progenitor cells that regenerate taste receptor cells.

Neurotransmitters in taste signaling

Serotonin and ATP released from taste cells to activate afferent nerves.

Chorda tympani

Branch of facial nerve (VII) carrying taste from the anterior two-thirds of the tongue.

Cranial nerves VII, IX, X

VII (facial): anterior tongue; IX (glossopharyngeal): posterior tongue; X (vagus): epiglottis/oesophagus—carry gustatory information.

Nucleus of the solitary tract

First central gustatory nucleus in the medulla where taste afferents terminate.

VPM (ventral posteromedial nucleus)

Thalamic nucleus that relays gustatory information to cortex (insula/operculum).

Insular cortex (gustatory cortex)

Primary cortical region for taste perception; part of gustatory processing.

Orbitofrontal cortex

Secondary taste center involved in integrating taste with olfaction and signaling satiety.

Labelled line coding

Coding model where each taste quality travels along a dedicated peripheral pathway.

PTC tasting and bitter perception

Phenylthiocarbamide tasting ability varies; linked to T2R bitter receptor genes.

T2R receptor gene

GPCR gene family encoding bitter taste receptors; many subtypes.

T1R2/T1R3 and T1R1/T1R3 heterodimers

Receptor combos for sweet (T1R2/T1R3) and umami (T1R1/T1R3) tastes.

MSG

Monosodium glutamate; a glutamate source that elicits umami taste.

Gustatory map in insular cortex

Functional mapping showing region-specific responses to tastants (evidence of gustatory representation).