Lecture on Taste Perception

5 Main Tastes

• Bitter, Salty, Sweet, Sour, Umami (glutamate)
• Depend on specific receptors localized on the tongue

Distribution of Taste Buds

• Taste buds sprinkled throughout the tongue
• Highly localized in the anterior aspect
• 3 Types of Taste Buds:
  • Fungiform: Mostly in anterior part
  • Foliate: Found on the sides
  • Circumvallate: Located in the back

Structure of Taste Buds

• Each taste bud contains a mix of cells, each for a specific taste
• Cells detect bitter, salty, sweet, sour, and umami compounds
• Every taste bud can detect all 5 tastes
• Taste perception is not region-specific

Labelled Lines Model

• Each taste cell projects an axon to the brain
• Axons remain separate and synapse on different parts in the gustatory cortex
• Different taste regions in gustatory cortex (e.g., sweet, bitter)

Taste Cell Function

• Case study for a Sweet taste cell:
  • Sweet cell with receptors for glucose
  • Binding of glucose triggers signal, causing depolarization and action potential to the brain
• G-Protein Coupled Receptors (GPCR)
  • Receptors for sweet, umami, and bitter
  • GPCR triggers a cascade that depolarizes the cell
• Sour and Salty rely on ion channels
  • NaCl binds, opens receptor, allows positive ions in, depolarizes the cell

Experiment: Salty Receptor in Sweet Cell

• Sweet cell recognizes glucose
• Inserting a salty receptor (ion channel) makes the sweet cell react to NaCl
• Brain can't differentiate; interprets NaCl as sweet
• Demonstrates how labeled lines model keeps taste perception specific, despite receptor swaps

Key Terminology

• Gustation: Sense of taste
• Gustatory Cortex: Brain region for taste