Olfactory

Question 1

How many different odourants are there?

Answer 1

> 400 000

Question 2

How many features does the “dragon” system have?

Answer 2

5000

Question 3

How many olf receptor genes do humans have?

Answer 3

900 (500 pseudogenes not expressed)

Question 4

Which animal is macrosmatic?

Answer 4

mouse, elephant

Question 5

Which animal is microsmatic?

Answer 5

dolphin

Question 6

Are olf receptors GPCRs or LGICs?

Answer 6

GPCR in mammals, LGIC in insects

Question 7

What is the androstenone receptor?

Answer 7

OR7D4
sweat, celery, pork meat.
some people with point mutation find it pleasant, floral, or odorless.

Question 8

What is specific anosmia?

Answer 8

Specific anosmia - the absence of sense of smell for particular odour - ko for specific OR

Question 9

What is orthonasal turbinates?

Answer 9

air through nostrils

this moistens the air

Question 10

What is the name of olfaction which occurs during eating?

Answer 10

retronasal/nasopharynx

Question 11

Where is the olfactory nerve?

Answer 11

cribriform plate of ethmoid bone

Question 12

What are the secondary areas of olfactory processing?

Answer 12

piriform cortex, amygdala, cortical nucleus

Question 13

What is the structure of the olf epithelium?

Answer 13

pseudostratified epithelium; 1 layer but nuclei at different types
Main cell type is olf receptor neuron
Soma in middle of epithelium, 1 dendrite process to surface and give rise to cilia (area which contains R) embedded in mucus

Question 14

Which are the olf stem cells?

Answer 14

basal cells

Question 15

What is the role of supporting cells?

Answer 15

express odourant-binding proteins bind (hydrophobic) odourants and help them pass through mucosa
Also produce enzymes against toxins

Question 16

What is the role of LSD1?

Answer 16

LSD1 protein expressed in small amount in cytoplasm, is necessary for initiating transcription of olf Rs
Once olf R starts to be transcribed, LSD1 got rid of to maintain the R expression - LSD1 incompatible w maintenance of OR expression

Question 17

What are the main classes of olf Rs?

Answer 17

Class I fish-type for hydrophilic, class II tetrapod for hydrophobic molecules

Question 18

What are the downstream effects of G-olf activation?

Answer 18

1 GDP, activated ACIII, ATP→ cAMP → CNGC so Na and Ca enter cell → Ca binds CaCC (ca activ chloride channel) , Cl- leaves cell → cell depolarisation
cAMP binds PKA → phosphorylate olf receptors, decrease activity
Ca binds Calmodulin, CaM-Ca binds CNGC to decrease activity, activate CaMKII phosphorylates ACIII to reduce activity decreasing cAMP production

Question 19

How many glomeruli are there?

Answer 19

2 glomeruli for each R in one bulb (4 for each R type)

Question 20

How are axons guided as they grow into brain?

Answer 20

SEMA3A-NRP1 released into ec space, sensed by neuropilin Rs which can make axon turn away