Chemical Senses Flashcards
What does the neuroepithelium contain?
olfactory sensory neurons
basal cells
supporting cells
How are new olfactory nerves positioned?
to a specific glomerulus to depending on the receptor type they express
What are the targets of the Main olfactory epithelium and the vomeronsal eptithelium?
main olfactory bulb and the accessory olfactory bulb
What cells are required to help transduce the signal from the nasal epithelium to the olfactory system?
mitral cells granule cells (inhibitory interneurons which connect the mitral cells) periglomerular cells (inhibitory interneurons)
what is the cribriform plate?
a bony structure with tiny holes through which the olfactory sensory neurons pass through
what are odorant receptors related to?
tast receptors, odorant receptors, gustatory receptors, drosophila odour
What is the sequence of events in olfactory signal transduction?
odorant binds odorant binding protein and activates Golf.
this stimulates AC and generates cAMP
cAMP opens cAMP dependent cation channels
Ca opens Cadependent Cl channels
Cl flows out depolarising the cell and release of glutamate
What is unusial about the cl concentration of the olfactory epithelium?
it is high intracellularly because of NKCC1 incase Na on its own is not enough to generate a response
why may the olfactory signalling pathway end?
ensymes break down odourant
cAMP activates inhibitory pathways
adaptation
how does the olfactory pathway adapt?
via Ca which enters through CNG proteins which provide adaptation via negative feedback. as ca increases it acts on the channel to decrease its sensitivity to cAMP which in turn requires a higher response to activate it
What is the glomerulus?
spherical structure containing the incoming axons of the OSN and is the first processing station of the brain
what is the function of the periglomerular cell?
inhibits in the glomerular layer by connecting one glomerulus to the other
What is the function of the granule cell?
inhibits one mitral cell from another in the granule cell layer
what is the function of the mitral cell?
receives odor information and refines and amplifies the signal via the Granule cell and periglomerular to then relay the message
What are the olfactory tracts?
the hypothalamus, the thalamus, the amygdala and other rregions of the limbic system
Where is the olfactory information sent from the thalamus?
to the piriform lobe of the olfactory cortex and the frontal lobe
Where is the olfactory information sent via the amgydala?
to innervate emotional responses and does this successfully by avoidance of the thalamus helping form memories associated with scents
What is specific about the threshold of the olfactory receptors?
the odourants need to dissolve into the mucus of the olfactory epithelium. some only need nano molar concentrations i.e. methyl marcaptan - in garlic
How is the epithelium organised?
into four main zones which project to specific glomeruli
how might many more scents than receptors be known?
one odour may activate many receptors and one receptor may responsd to many odours. it is the pattern that matters
What are the primary tastes?
sour (H ions), salt (Na and K), bitter (poison, caffeine), sweet (sugars), umami (yummy stuff)
What different forms of pappillae that you can have?
circumvillate
fungiform
foliate
filliform - mechanical not gustatory
how is taste sensed?
the saliva goes over the taste pore and microvilli are exposed to taste - not very specific
What is the transduction mechanism for salty foods?
opens amiloride sensitive Na channels ENaC - Na enters cell and depolarises
