Olfactory Flashcards
How many different odourants are there?
> 400 000
How many features does the “dragon” system have?
5000
How many olf receptor genes do humans have?
900 (500 pseudogenes not expressed)
Which animal is macrosmatic?
mouse, elephant
Which animal is microsmatic?
dolphin
Are olf receptors GPCRs or LGICs?
GPCR in mammals, LGIC in insects
What is the androstenone receptor?
OR7D4
sweat, celery, pork meat.
some people with point mutation find it pleasant, floral, or odorless.
What is specific anosmia?
Specific anosmia - the absence of sense of smell for particular odour - ko for specific OR
What is orthonasal turbinates?
air through nostrils
this moistens the air
What is the name of olfaction which occurs during eating?
retronasal/nasopharynx
Where is the olfactory nerve?
cribriform plate of ethmoid bone
What are the secondary areas of olfactory processing?
piriform cortex, amygdala, cortical nucleus
What is the structure of the olf epithelium?
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
Which are the olf stem cells?
basal cells
What is the role of supporting cells?
express odourant-binding proteins bind (hydrophobic) odourants and help them pass through mucosa
Also produce enzymes against toxins
What is the role of LSD1?
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
What are the main classes of olf Rs?
Class I fish-type for hydrophilic, class II tetrapod for hydrophobic molecules
What are the downstream effects of G-olf activation?
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
How many glomeruli are there?
2 glomeruli for each R in one bulb (4 for each R type)
How are axons guided as they grow into brain?
SEMA3A-NRP1 released into ec space, sensed by neuropilin Rs which can make axon turn away
