Gustatory system

Question 1

What is the stimulus for umami tastes?

Answer 1

• Savoury taste of glutamate

- Associated with MSG

Question 2

How do we perceive flavours?

Answer 2

Different receptors for:
- Taste
- Texture 
- Smell 
Combined in the cortex

• Mixture of receptors for different tastes can be activated

Question 3

Why are bitter tastes instintively rejected?

Answer 3

Often poisons

Question 4

Which tastes have metabotropic receptors?

Answer 4

Bitter, sweet and umami

Question 5

What is the processs of transduction for sour tastes?

Answer 5

• H+ into cell (as stimulus)
• Slightly depolarises, opening voltage gated Na+ channels
• Increases membrane potential
• Voltage gated Ca2+ channels open
• Release of neurotransmitter (5-HT)

Question 6

What are the 4 types of lingual papillae?

Answer 6

1) Circumvallate
2) FIliform
3) Fungiform
4) Foliate

Question 7

Describe foliate papillae

Answer 7

• Least abundant

- Only present for the first 2-3 years of life

Question 8

Which tastes have ionotropic receptors?

Answer 8

Sour and salty

Question 9

What is the stimulus for sour tastes?

Answer 9

H+

Question 10

What do basal cells do?

Answer 10

Produce new taste cells every 10 days

Question 11

What is the structure of the lingual papillae?

Answer 11

• Taste buds line the pores next to papilla
• ~100 taste cells (receptors) in taste buds
• Taste cells have microvilli which project into the taste pore and detect stimulus
• Have synapse at the base

Question 12

Describe circuvallate papillae

Answer 12

• At the back of the tongue

- Bitter stimuli

Question 13

Describe filliform papillae

Answer 13

• No taste buds
• Most abundant
• Sense texture
• Along the centre of the tongue

Question 14

Describe fungiform papillae

Answer 14

• Along the tip and sides of the tongue

- Sweet, sour, salty

Question 15

What is the stimulus for salty tastes?

Answer 15

Na+, Cl-

Question 16

How are bitter, sweet and umami tastes differentiated from eachother?

Answer 16

Different subtypes of metabotropic receptor

• Bitter: T2R
• Sweet and umami: T1R

Question 17

What is the processs of transduction for bitter, sweet and umami tastes?

Answer 17

• Phospholipase C activated
• Causes PIP2–> IP3, which causes Ca2+ to be released from stores
• Activates TripiM5 channel, allows Na+ into cell
• Depolarise cell
• Voltage gated Na+ channels open
• Graded potential
• ATP released through channel, activates the gustatory neuron