Gustation

Question 1

What are the basic tastes?

Answer 1

Basic Taste Qualities
• Salty (sodium chloride)
• Sour (acid)
• Sweet (sugar)
• Bitter (wide range of molecules, many toxic) Fifth Taste Quality
• Umami (monosodium glutamate)

Question 2

What are the components of a gustatory system ?

Answer 2

Basal cells—> division and differentiation/regeneration

Microvilli —> increase surface area (transduction area)

CN VII (Anterior tongue)
CN IX (Posterior tongue)
CN X (Epiglottis)

Question 3

Describe gustatory signal transduction

Answer 3

• Tastants may:
• Directly pass through ion channels (salt and sour)

• Bind to and block ion channels (sour)

• Bind to G-protein-coupled receptors that lead to ion channel
opening (bitter, sweet, umami; G-protein e.g. gustducin)

Question 4

Contrast salt and sour signal transduction

Answer 4

Ionotropic signal transduction
• Salty (Na+ ions)
• Sour (H+ ions)

Taste ion→Current through ion channel→ Depolarization → Transmitter release

Question 5

Contrast sweet and bitter signal transduction

Answer 5

Metabotropic signal transduction

• Sweet (second messenger cAMP)
• Bitter (second messenger IP3)Taste molecule→Receptor binding → G-protein → Enzyme →Second messenger→ Current through ion channel→ Depolarization → Transmitter release

Question 6

Give a gustatory pathway overview

Answer 6

1. Primary gustatory neuron.
2. Secondary gustatory neuron, soma in rostral solitary nucleus.
3. Tertiary gustatory neuron, in VPM of thalamus.

Peripheral nerve fiber (CN VII, IX or X) synapse in solitary nucleus and bifurcates in the rostral pons and 2/3 go to insula and operculum

1/3 goes to VPM of thalamus