Taste Sensing and Processing

Sensing of Taste Signals

• Taste papillae are found on the tongue and parts of the palate
• There is no taste map, and all flavors are sensed in different areas, although there are differences in abundance

Taste Buds

• There are different types of taste cells:
  • Type I: supporting, glial-like cells (50%)
  • Type II: sweet, bitter, umami (33%), express 1 class GPCR
  • Type III: sour, no GPCR
  • Type IV: precursors?

Transduction of Gustative Signals

• There are 5 basic tastes: salty, sour, bitter, sweet, and umami
• Sour/salty signals are processed via activation of ion channels
• Umami/bitter/sweet signals are processed via GPCR activation and transporters
• Sweet/Bitter/Umami taste signals are mediated by GPCRs
• There are 2 taste receptor families: T1R (Sweet/umami) and T2R (Bitter)

Salt and Sour Taste Signals

• Salty taste signals are mediated by ion channels (Amiloride-sensitive receptors)
• Sour taste signals are mediated by ion channels (PKD2L1, Otopetrin 1)

Taste Cell Transduction Mechanisms

• Type II Cells: Sweet/umami/bitter taste sensing, no vesicles or voltage-gated Ca2+ channels
• Type III Cells: Sour taste sensing, contain synaptic vesicles, may use multiple neurotransmitters

Processing of Sweet Taste

• Type II taste cells detect natural and artificial sweet compounds using different receptor combinations
• Activation of transporters may provide nutritional value

Interaction Between Tastes

• Salty and sweet foods interact, with salt perceived as sweet
• There is a complex interaction between different taste cell types

Cellular Sensing of Tastes

• Taste cells respond to one taste modality
• One individual taste cell can express several T2R, responding to different bitter molecules
• Taste perception involves the interaction between somatosensory, gustative, and olfactive signals

Role of Chemoreceptors

• Chemosensory intestinal cells possess taste receptors and other chemoreceptors
• There is a relationship between taste and nutritional/toxic value

The Combinatorial Model of Taste Coding

• Taste is needed to detect food sources and avoid spoiled/toxic substances
• Taste signals are relayed to higher-order neurons (CNS)

Gustative Processing Pathways

• Information reaches the CNS through VII, IX, X cranial nerves
• Relay on the NTS, with divergent pathways ensuing
• Concious and emotional taste processing pathways exist

Cortical Gustotopic Map

• A cortical gustotopic map (insular gustative cortex) was suggested for different tastes (other than sour)
• There is conflicting evidence on the existence of this map

This quiz covers the sensing of taste signals, including the role of taste papillae and buds on the tongue and palate, and debunks the myth of the taste map.