Taste (Gustation)

Taste in Survival

• Identify Nutritious Food

• Avoid Poisonous Foods (typically bitter)

Five Tase Modalities

1. Sweet (Sugars → caloric energy)

2. Salty (sodium → mineral balance)

3. Umami (glutamate → protein/amino acids)

4. Sour (acids → potential toxicity)

5. Bitter (alkaloids → poison warning)

Taste pore & microvilli

Exposed to saliva. Receptor proteins on microvilli bind dissolved tastants.

Taste receptor cells (TRCs)

NOT neurons; release glutamate onto gustatory nerve fibers

Gustatory stem cells

Renew TRCs every ~10 days. Constant turnover because the oral environment is harsh.

Gustatory Nerves

First neuron in pathway. Carries signals from tongue → nucleus of the solitary tract in brainstem

SALTY ion channel — ENaC channel

→ Tastant: NaCl (Na⁺ ions)

→ High [Na⁺] in saliva opens the channel

→ Na⁺ flows in → depolarization → neurotransmitter release

SOUR — Acid-sensing channel

→ Tastant: H⁺ ions (acidity)

→ Low pH opens a proton-sensitive ion channel

→ H⁺ and Na⁺ flow in → depolarization

Spicy Hot & Minty Cool

not tastes — they're thermosensation via TRP ion channels, not taste receptor cells.

• Capsaicin → TRPV1 (heat-sentive Ca²⁺ channel)

• Menthol → TRPM8 (the cold receptor)

Gustatory Pathway

Toungue → Brainstem → Thalamus → Cortex

Brainstem → Amygdala/Hypothalamus

• Fast, reflexive responses to taste

• Regulating emotional responses (disgust, etc.)

• Regulating physiological responses (salivation, etc.)

Brainstem → Thalamus → Cortex

• Conscious perception and evaluation Recognition

• Integrating taste with smell and texture

• Decision-making about food choices

Learned Associations: Conditioned Taste Aversion

Rats condtitioned to associate certain foods with nausea → causes the rats to avoid that food

Flavor is Multisensory

• Depends of smell, texture, sound of food, visual