The olfactory system

Question 1

What receptor type is involved in olfaction?

Answer 1

GPCRs

- Many different receptors but all are coupled with the G protein Golf

Question 2

Where do the olfactory projections go?

Answer 2

• Hypothalamus (sex and neuroendocrine)
• Reticular formation (visceral responses)
• Amygdala (emotional responses)
• Hippocampus (olfactory memory)
• Olfactory cortex (concious smell)

Question 3

What are glomeruli?

Answer 3

• Little areas of the olfactory bulb which are associated with a certain type of receptor
• One on each side of the hear
• Each specific receptor TYPE sends projections to the glomeuli on either side of the head

Question 4

What is the structure of the olfactory epithelium?

Answer 4

Mucus layer
- Bathes cilia of olfactory receptor cells

Supporting cells and olfactory receptor cells
- Supporting cells secrete the mucus

Basal cells
- Produce new olfactory receptor cells (one of the only neurons to be replaced)

Question 5

What are the features of the olfactory receptor cells?

Answer 5

• Receptor cells are both the sensory receptor and the primary afferent neuron
• Thin and unmyelinated
• Project through the cribiform plate and into the olfactory bulb (in the forebrain)
• Form the olfactory nerve

Question 6

What happens in the mucus layer of the olfactory epithelium?

Answer 6

• Odorant molecules dissolve in the mucus

- Cilia which bathe in the mucus is where the transduction machinery is

Question 7

What is the olfactory epithelium?

Answer 7

• Small, thin sheet of cells
• High up in the nasal cavity
• Used to smell (NOT THE NOSE)

Question 8

What do the cilia in the olfactory epithelium have high levels of Cl-?

Answer 8

So when ANO2 channels are open, Cl- moves OUT, increasing the depolarisation of the membrane

Question 9

What is the olfactory pathway?

Answer 9

• Activate GPCR which activates adenylyl cyclase
• ATP –> cAMP
• Opens a cyclic nucleotide gated channel (CNG)
• Na+ and Ca2+ into the cell
• Opens ANO2 (Cl- channel)
• Cl- OUT of the cell
• Causes further depolarisation which spreads fro the cilia into the main dendritic portion
• Action potential if above thereshold