Olfaction and Taste

Question 1

What is the central olfactory pathway?

Answer 1

odorant -> olfactory cell -> olfactory bulb -> limbic system (repro, memory, motivation)

Question 2

What happens when an odorant binds to a receptor?

Answer 2

1. Odorant binds to G protein coupled receptor
2. This activates adenyl cyclase
3. Increases production of cAMP
4. Na and Ca channels open
5. Influx of Na and CA causes depolarisation and generation of an AP

Question 3

How can smell be localised?

Answer 3

By lateral inhibition between R and L nostril

Question 4

What are the flavours animals can taste?

Answer 4

• salty - Na, Cl channels
• sour - measure of acidity
• bitter - measure of poisons *can’t differentiate between bitter tastes*
• sweet - single receptor
• umami - msg? not always detectable

Question 5

How do salty/sour taste receptors work?

Answer 5

1. Ions enter receptor cells through ion channels in microvilli
2. Causes depolarisation and opening of Ca channels
3. Ca influx causes NT vesicles to fuse to membrane
4. NT released, AP generated in associated neurone

Question 6

How do bitter/sweet receptors work?

Answer 6

1. Binds to G protein linked receptor on microvilli
2. G protein is activated and intracellular Ca is released
3. NT vesicles are released and they fuse with presynaptic cell membrane
4. NT released, AP generated in associated neurone

Question 7

What is the central taste pathway?

Answer 7