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Neuro 223 > Module 7 > Flashcards

Module 7 Flashcards

1
Q

characterize the peripheral and central organization of the gustatory system

A
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2
Q

discuss sensory transduction in gustatory receptor cells

A
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3
Q

describe information coding in the gustatory system

A
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4
Q

characterize the peripheral and central organization of the olfactory system

A
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5
Q

discuss sensory transduction in olfactory receptor cells

A
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6
Q

describe information coding in the olfactory system

A
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7
Q

can an odor be responded to at different concentrations?

A

yes, ex. indole smells of flowers at low concentrations and purtrid at high concentrations (could be a result of affinity to receptors)

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8
Q

structure of olfactory system

A
  1. odorants (inhaled in)
  2. layer of mucus, within mucus, are the olfactory cilia, the chemicals must dissolve in the mucus
  3. the cilia are connected to an olfactory knob
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9
Q

is an odor always detectable as the same scent?

A

no, can depend on concentration and how affects receptors

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10
Q

process of olfaction

A
  1. scent inhaled, dissolved in mucus layer
  2. binds to olfactory cilia attacked to ORNs
  3. travels through olfactory knob and affects mature ORNs
  4. the neurons innervate glomeruli which contact downstream mitral cells
  5. mitral cels project to the olfactory cortex
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11
Q

what are glomerulus?

A

circles of coalescing neurons, neurons with same receptor projects to the same glomerulus, 25,000 ORN’s can project to a single glomerulus

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12
Q

how does olfactory system distinguish between smells?

A

activates receptors with the same features as molecule, molecule can have multiple features, but each feature will end together at a single glomerulus

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13
Q

what are basal cells?

A

produce stem cells as developing ORNs that replenish damaged mature ORNs

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14
Q

what does bowman’s gland do?

A

secretes mucus

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15
Q

what is the purpose of mucus?

A

helps protect against harmful odorants, although more mucus decreases olfactory acuity

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16
Q

where do ORNs receive signals?

A

ONLY at the cilia

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17
Q

odorant receptors

A

most are GPCRs, 7 TM receptor

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18
Q

process of olfactory receptor activation

A
  1. activated by ligand
  2. Ga (in this case, Golf), binds to GPT and with ATP at adenyl cyclase III, activates CAMP (second messenger)
  3. activates ion-gated channel leading to depolarization and activation other ion channels and exchangers (positive in, - out)
  4. depolarizes membrane
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19
Q

combinatorial odor code

A

can activate multiple receptors based on how many features a molecule has (most odorants activate multiple glomeruli)

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20
Q

how does a signal from the mitral cell reach the cortex?

A

afferent inputs: OSN to GL to mitral cells to olfactory cortex

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21
Q

what inhibition are signals from mitral cells to olfactory cortex faced with?

A

granule cells: top-down inputs and map onto mitral cells, mitral cells can release glutamate which causes granule cell to release GABA back at mitral cell, essentially turning it off (reciprocal synapse bc can send and receive info)

Periglomerular cell: does the same thing, but from OSN to mitral cells

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22
Q

how do chemical signals map onto the pyriform cortex?

A

aren’t many patterns when just a few receptors activated, but when multiple receptors activated, can see a specific pattern that is specific to each molecule
*added caged glutamate as opposed to full glutamate bc after to activate receptors

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23
Q

the model of pyriform cortex activation in olfactory system

A

need all receptors of molecules’ features to fire to activate cortical response

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24
Q

what are olfactory bulb targets?

A

The pyriform cortex, olfactory tubercle, amygdala, and entorhinal cortex are mapping on to…
orbitofrontal cortex, thalamus, hypothalamus, hippocampal formation

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25
Q

gustatory system nerves

A
  1. gustatory cells of the tongue, go to cranial nerves
  2. nucleus solitarius maps to thalamus
  3. thalamus maps to primary gustatory cortex in insula of cerebrum
26
Q

where are taste buds?

A

tongue, inside cheeks, soft palate, pharynx, epiglottis

27
Q

what is the lingual papillae

A

to distinguish food texture, taste

28
Q

classes of taste

A

bitter, sour, sweet, meaty (umami), salty

29
Q

elements of a taste bud

A

receptors for each class of taste (taste cell), supporting cells, taste pore as taste hairs at the top of the taste bud (this is the receptor surface), and the other side has synaptic vesicles and synaptic nerve fibers that innervate the taste buds, there are also basal cells to replace damaged cells

30
Q

how can things be tasted?

A

molecules must dissolve in saliva and flood a taste pore

31
Q

why is salty taste important?

A

important for electrolyte balance

32
Q

why is sweet taste important?

A

indicates carbs and foods with more calories, as calories are needed for survival

33
Q

why is sour taste important?

A

acids, citrus fruits

34
Q

why is bitter taste important?

A

to keep you from eating toxic things (ex. spoiled foods, nicotine, caffeine, morphine)

35
Q

why is umami taste important

A

savory meat taste, protein

36
Q

are hot peppers a taste?

A

no just act on TRPVI in nociceptors, not taste buds

37
Q

how is taste innervated?

A

olfactory eventually converges with gustatory pathway

38
Q

where is gagging on the tongue?

A

at back of tongue

39
Q

salty receptors

A

sodium ion chanel

40
Q

sour receptors

A

ph (H+) ion channel which inhibit inward K+ channel

41
Q

sweet receptors

A

TIR2 and TIR3 proteins (dimerize into a fly trap)

42
Q

amino acid (umami) receptors

A

TIR1 and TIR3 proteins (dimerize into a fly trap)

43
Q
A
44
Q

bitter receptors

A

T2R protein

45
Q

which receptors have high threshold for action potential in gustatorial system?

A

salty, sour, and sweet

46
Q

which receptors work via IP3 causing Ca influx via TRPM5 channels?

A

sweet, umami, bitter

47
Q

how to block a channel

A

if KO just one protein in class receptor, it doesn’t work

48
Q

type 1 taste cells

A

glial cells, supporting other epithelial cells can regulate ionic environment

49
Q

type 2 taste cells

A

chemosensory receptor cell for sweet, bitter, umami, salty tastants has 1 or 2 classes of cell receptors (excitable and releases ATP and channel synapse)

50
Q

type 3 taste cells

A

chemsensory receptor for sour tastants, releases nt (serotonin)

51
Q

type 2 cells in action

A

2 paths:

the first…
1. salty ions glow through Na+ ion channel

the second…
1. sweet, bitter, or umami ions bind to the GPCR, and the a and g subunits bind to PLCb2 on the membrane
2. this releases IP3 which acts on Ca2+ on ER
3. the Ca2+ channel opens and causes the TRPM5 channel to open, depolarizing the membrane

they converge:
1. voltage gated ion channel opens as a result of the depolarization
2. this causes the CALHM ATP channel to open and release ATP
3. the ATP bind to the gustatory afferent axon at the P2X adenosine receptor
4. this propogates depolarization in the neuron

52
Q

type 3 cells in action

A
  1. sour acid enter via H+ ion channel (depolarizing the cell)
  2. this causes the voltage-gated ion channel to open and the voltage-gated Ca2+ channel to open
  3. the Ca2+ cause the serotonin vesicles to merge with the membrane and rush across to the gustatory afferent axon serotonin receptor
53
Q

what level of nutrients need to be present to promote a response?

A

large amount, because body only responds to large levels of essential nutrients

54
Q

label line coding neural theory

A

taste neurons each have a dedicated specific taste quality carried by a unimodal taste receptor cell to cortex, each are represented individually in a taste bud

55
Q

across neuron pattern neural theory

A

perception of taste from a combination of multiple neurons, individual neurons can respond to multiple tastes (don’t have to be specialists)

56
Q

which theory of neural coding theory prevails?

A

evidence for both

57
Q

cranial nerve pathways

A

cranial nerve VII: input from first 2/3 of tongue, sends to ganglion VII
cranial nerve IX: input from posterior 1/3 of tongue, sends to ganglion IX
cranial nerve X: input from pharynx, upper esophagus, sends to ganglion X

58
Q

where do cranial nerves go?

A
  1. taste buds
  2. cranial nerves
  3. ganglion
  4. nucleus of the solitary tract (kind of behind brain stem at top of spine)
  5. VPMpc of thalamus to insular and frontal gustatory cortices OR hypothalamus and amygdala to insular and frontal gustatory cortices
59
Q

old thinking of gustatopic map

A

spatial coding

specific cells activated in cortex based on class of neurons

60
Q

current thinking of gustatopic map

A

temporal coding

behavior of neurons (firing rate) impacts the perception of taste class (firing rate over time affects perception)

Neuro 223 (5 decks)

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