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BMS153 NEUROSCIENCE > Smell and taste > Flashcards

Smell and taste Flashcards

1
Q

chemical senses

A

are the oldest and most common form of sense

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2
Q

function of chemical sense

A

identify food sources
avoid noxious substances
find a mate or mark territories

Even bacteria can sense chemical (chemotaxis)
Primitive function
Eg dogs use pheromones to detect a mate

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3
Q

gustatory system and olfactory system differences

A

have separate transduction mechanisms
information is processed in parallel
information is merged in the CNa

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4
Q

5 basic tastes

A 
salty 
sour
sweer
bitter
umami
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5
Q

salty

A

vital electrolytes, ionotropic receptor

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6
Q

sour

A

acids, H+ inotropic receptors - fatty acids

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7
Q

sweet

A

innante fondess, high energy foods, metabotropic receptors (g protein coupled)

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8
Q

bitter

A

instinctively rejected, often poisonous, metabotropic receptor

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9
Q

umami

A

delicious in japanese
savoury taste of GLUTAMATE (excitatory neurotransmitter, and amino acid for protein, metabotropic receptor (MSG in fast foods)

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10
Q

perception of flavour

A

mixture of the receptors activates

and receptors for texture and temperature receptor

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11
Q

craving

A

when deficit in nutrients

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12
Q

where taste smell touch combined

A

in the cortex

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13
Q

correct concs of sodium and potassium is really important

A

will crave salty foods if not enough sodium in body

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14
Q

lingual papillae

A

taste-sensing strutures

lumpy structures of tongue

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15
Q

taste organs

A

tongue, cheeks, soft palate, pharynx, epiglottis

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16
Q

most sensitive flavours

A

sour and bitter

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17
Q

4 types of lingual papillae

A

filliform
foliate
fungiform
circumballate

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18
Q

filliform

A

spiked, no taste buds, sense texture, most abundant

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19
Q

foliate

A

ridges, least abundant, gone by 2-3 years

20
Q

fungiform

A

mushrooms, mainly at sides and front

21
Q

circumvallate

A

pimples, large, contain about half of all taste buds

22
Q

taste buds contain

A

taste cells and gustatory afferents

23
Q

number of taste buds

A

2000-5000

about 100 taste cells per taste bud

24
Q

taste pores

A

allows stimulus detection by micro villi

25
Q

gustatory afferents carry

A

information to central nervous system

26
Q

papillae have

A

pores where stimulus enters

side of papillae is where taste bud sits

27
Q

taste cells

A

become thin at apex, projecting into taste pore, transducer stimuli into electrical signal

28
Q

basal cells

A

like stem cells, renew taste cells every 2-3 weeks

29
Q

bitter, sweet, umami transduction mechanism

A

similar systems

(just slightly different receptors but all g protein coupled receptors)

metabotropic
no synaptic vesicles
uses ATP

1) Activation of g protein coupled receptor
2) Activate PLCB2
3) And then iP3
4) Ca released from intracellular stores
5) TrpM5 opens and allows sodium and calcium to enter cell\
6) Sodium moving in causes depolarisation in taste cell
7) VGNC (voltage gated sodium channel) opens causing depolarisation further
8) Release of neurotransmitter at base of cell – ATP is acting as the neurotransmitter
9) ATP moves out of channel

30
Q

sour transduction mechansism

A

ionotropic
synaptic vesicles
uses 5-HT, GABA, ATP

1) Ion channels at apical tips permeable to hydrogen ions
2) Already depolarising the cell (so the stimuli itself is already starting the process of depolarisation)
3) Opening of VGNC further depolarisation
4) Activating VGCC (calcium channels) allow calcium into cell
5) Activates the release of synaptic vesicles – a variety of neurotransmitters in vesicles : HT, GABA, ATP

31
Q

taste cells threshold

A

they have different threshold for different basic tastes- ‘preferences’

e.g. gustatory axons labelled red receive most inputs from taste cells that respond best to sucrose (sweet), but they also receive input from taste cells that respond to other basic tastes

One taste cell can respond to sweet and salty stimuli for example, but will respond best to one of these stimuli, as it will be detected at a lower threshold.

32
Q

Gustatory afferents from anterior 2/3rds of tongue are carried in

A

facial nerve, cranial nerve VII.

33
Q

logistics of specific taste receptors

A

We cannot have a completely specific labelled line code, otherwise every flavour would need a specific taste receptor – we don’t have enough proteins for that. So we need to combine the responses of many gustatory afferents using population coding.

34
Q

odorants

A

detected as low as a few parts per trillion
must dissolve in the music later to reach olfactory cells
can’t detect chemicals in the air

cavity behind the nose that sense smells

35
Q

the olfactory receptors re

A

on the cilia that protect mucsus where the adroitness are dissovled

Axons (thin and unmyelinated) will form cranial nerve I (olfactory nerve)
Basal cells help produce new olfactory neurons (newly made in adults in humans)

36
Q

transduction occurs via specific g-protein coupled receptors

A

all odorant receptors are g protein coupled

every one uses the same downstream pathway

When G (olf) activated,
Activate somethhing clycalse and then cAMP
Which opens other ion channels (CNG- cyclic neuclotide gated channel)
Sodium and potassium – graded potential in cilia (dendrite part)
ANO2 allows cholride into and out of cell
Further depolarisation of Cl moving out

37
Q

anosmic

A

Golf knock out mice are anosmic i.e. they cannot smell.

38
Q

odorant receprotr protein genes comprise how much of the entire genome

A

about 3-5 %

39
Q

Graded receptor potential
Enough of odorant around to enough of a potential
Produces spikes of AP if above threshold

A

Large enough receptor potential = threshold for action potential firing reached

Intense stimulus = large receptor potential = increased action potential firing rate

40
Q

glomerulus of olfactorybulb

A

received input from the olf receptor cells expressing one specific olf receptor

second order neutron carry info from the glomeruli to various regions of the brain

41
Q

olfactory projections - conscious smell

A

conscious smell- olfacotry cortex

42
Q

olfactory memory

A

hippocampus

43
Q

emotional responses

A

amygdala

44
Q

visceral responses

A

reticular formation

45
Q

sex & neuroendocrine

A

hypothalamus

46
Q

which sensory cells release ATP via ion channels rather than synaptic vesicles

A

taste cells responsive to bitter, umami and sweet

ion channel called calcium homeostasis modulator 1 (CALMH1) when they are stimulated.

CALMH1 is a voltage-gated ion channel that opens as the taste cells depolarise in the sequence of downstream events that occur following the activation of G-protein coupled receptors by bitter, sweet or umami stimuli.

47
Q

which sensory cells use synaptic vesicles

A

sour and potentially salty stimuli

don’t use g protein coupled receipts

instead depolarise due to activation of ion channels - traditional method of synaptic vesicle fusion to release their neurotransmitter onto the primary afferent heron when they depolarise

BMS153 NEUROSCIENCE (24 decks)

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