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Sensory and Motor Neuroscience > Chemical Senses > Flashcards

Chemical Senses Flashcards

1
Q

What does the neuroepithelium contain?

A

olfactory sensory neurons
basal cells
supporting cells

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2
Q

How are new olfactory nerves positioned?

A

to a specific glomerulus to depending on the receptor type they express

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3
Q

What are the targets of the Main olfactory epithelium and the vomeronsal eptithelium?

A

main olfactory bulb and the accessory olfactory bulb

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4
Q

What cells are required to help transduce the signal from the nasal epithelium to the olfactory system?

A 
mitral cells
granule cells (inhibitory interneurons which connect the mitral cells)
periglomerular cells (inhibitory interneurons)
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5
Q

what is the cribriform plate?

A

a bony structure with tiny holes through which the olfactory sensory neurons pass through

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6
Q

what are odorant receptors related to?

A

tast receptors, odorant receptors, gustatory receptors, drosophila odour

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7
Q

What is the sequence of events in olfactory signal transduction?

A

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

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8
Q

What is unusial about the cl concentration of the olfactory epithelium?

A

it is high intracellularly because of NKCC1 incase Na on its own is not enough to generate a response

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9
Q

why may the olfactory signalling pathway end?

A

ensymes break down odourant
cAMP activates inhibitory pathways
adaptation

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10
Q

how does the olfactory pathway adapt?

A

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

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11
Q

What is the glomerulus?

A

spherical structure containing the incoming axons of the OSN and is the first processing station of the brain

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12
Q

what is the function of the periglomerular cell?

A

inhibits in the glomerular layer by connecting one glomerulus to the other

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13
Q

What is the function of the granule cell?

A

inhibits one mitral cell from another in the granule cell layer

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14
Q

what is the function of the mitral cell?

A

receives odor information and refines and amplifies the signal via the Granule cell and periglomerular to then relay the message

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15
Q

What are the olfactory tracts?

A

the hypothalamus, the thalamus, the amygdala and other rregions of the limbic system

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16
Q

Where is the olfactory information sent from the thalamus?

A

to the piriform lobe of the olfactory cortex and the frontal lobe

17
Q

Where is the olfactory information sent via the amgydala?

A

to innervate emotional responses and does this successfully by avoidance of the thalamus helping form memories associated with scents

18
Q

What is specific about the threshold of the olfactory receptors?

A

the odourants need to dissolve into the mucus of the olfactory epithelium. some only need nano molar concentrations i.e. methyl marcaptan - in garlic

19
Q

How is the epithelium organised?

A

into four main zones which project to specific glomeruli

20
Q

how might many more scents than receptors be known?

A

one odour may activate many receptors and one receptor may responsd to many odours. it is the pattern that matters

21
Q

What are the primary tastes?

A

sour (H ions), salt (Na and K), bitter (poison, caffeine), sweet (sugars), umami (yummy stuff)

22
Q

What different forms of pappillae that you can have?

A

circumvillate
fungiform
foliate
filliform - mechanical not gustatory

23
Q

how is taste sensed?

A

the saliva goes over the taste pore and microvilli are exposed to taste - not very specific

24
Q

What is the transduction mechanism for salty foods?

A

opens amiloride sensitive Na channels ENaC - Na enters cell and depolarises

25
Q

What is the transduction mechanism for sour foods?

A

acid sensing ion channels

proton sensitive potassium leak channels - H ions block these channels causing depolarisation

26
Q

How is bitter transduce?

A

use of T2 GPCR bitter receptors
couple to Gq to release PLC and increase Ca through IP3
others use gustaducin to activate cyclic nucleotide PDE
some block K leak channels

27
Q

What is the transduction mechanism for sweet?

A

use GPCRS T1R1 and T1R3
act through Gs to produce cAMP and PKA and close K channels through phosphorylation
some like aritficial sweeteners activate PLC to increase IP3 and Ca
Umami may also work this way

28
Q

Do taste maps exist?

A

barely

sweet/salt at front, sour at sides and bitter at back

29
Q

What is the pattern coding mechanism for taste?

A

the stimulus will activate all receptors in different manners and proportions then the CNS decodes the signals due to intensity and quality

30
Q

What is the sensitivity of taste to different flavours?

A

Bitter>salty,sour,sweet>umami

31
Q

How is the tongue innervated?

A

facial nerve along the tongue
the glossopharyngeal nerve at the back of the tongue
the vagus nerve in the epiglottis region
all feed into the nucleus of the solitary tract

32
Q

Where does the nucleus of the solitary tract go?

A

ventral posterior nucleus of the thalamus and the primary and secondary gustatory cortex buried in the roof of the sylvian fissure in the posterior frontal lobe

33
Q

Where are responses to taste buds combined?

A

the orbital frontal cortex which also receives input from the primary somatosensory cortex and the inferotemporal corte in the what pathway

34
Q

How is the firing of taste neurons affected?

A

by the level of hunger for a specific food

35
Q

What is meant by the multimodal convergence of all the senses in the OFC?

A

all the senses converge information here

Sensory and Motor Neuroscience (8 decks)

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