Smell and taste

Question 1

What happens during olfaction (smell)?

Answer 1

• Breath in, air swirls around in the nasal cavities.

- Turbulence delivers airborne particles / compounds to olfactory organs

Question 2

What are olfactory receptors?

Answer 2

These are modified neurons with multiple cilia

Question 3

Approximately how many receptors are in 5cm2?

Answer 3

10 to 20 million

Question 4

Where are receptor cilia found?

Answer 4

embedded in a mucous

Question 5

Where is the mucous secreted by?

Answer 5

Bowmans glands

Question 6

How do compounds reach the olfactory organs?

Answer 6

Diffuse through mucous and should therefore be lipid and water soluble

Question 7

What happens during transduction?

Answer 7

• Dissolved compounds interact with receptors called – odorant binding proteins
• Odorant binding to receptor
• Activates enzymic conversion of ATP to cAMP, (via adenylate cyclase)
• cAMP opens Na channels
• Depolarisation to threshold
• Action potential to Olfactory cortex

Question 8

What are taste receptors (gustatory receptors)?

Answer 8

• Superficial surface of the tongue
• Pharnyx and larynx (used in children, not in adults)
• Specialised epithelial cells
• 3000 taste buds

Question 9

What are the different types of Lingual papillae and what are the different shapes?

Answer 9

-Filiform papillae (thread like)
-Friction, no taste buds
-Fungiform papillae (mushroom like)
~ 5 taste buds each
-Circumvillate papillae (rounded)
~ 100 taste buds each
-V formation at the back of the tongue

Question 10

How does taste vary and what channels do salt and sweet open and close?

Answer 10

-Chemicals contact the taste hair cells
-Bind to receptors
-Different tastes have different mechanisms
Salt receptors open Na channels, depolarise
Sweet receptors close K channels, depolarise

-CNS adapts / modulates sensitivity