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ZOOL 342 > Gustation > Flashcards

Gustation Flashcards

1
Q

What are the 2 roles for gustation?

A
  • evaluating the nutritional content of food
  • preventing the ingestion of toxic compounds
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2
Q

Where are taste buds located on the tongue?

A

on top of papillae

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3
Q

What are the 4 different types of papillae? Which ones have taste buds?

A
  • fungiform (taste buds)
  • circumvillate (taste buds)
  • foliate (taste buds)
  • filiform (NO taste buds)
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4
Q

Describe the shape/size of fungiform papillae. Do they have taste buds on them? Where are they located on the tongue?

A
  • large bumps
  • taste buds
  • located at tip of tongue
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5
Q

Describe the shape/size of circumvillate papillae. Do they have taste buds on them? Where are they located on the tongue?

A
  • dome-shaped bumps
  • taste buds
  • forms a V at back of tongue
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6
Q

Do foliate papillae have taste buds on them? Where are they located on the tongue?

A
  • taste buds
  • located at base of tongue
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7
Q

Describe the shape/size of filiform papillae. Do they have taste buds on them?

A
  • small bumps
  • no taste buds
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8
Q

TRUE or FALSE: the distribution map for different tastes is all the same because each taste bud can have all different taste receptors

A

TRUE

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9
Q

What are the tastes that we can detect?

A
  • bitter
  • salty
  • sweet
  • umami
  • sour
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10
Q

What kinds of food are considered umami?

A

foods rich with glutamates like MSG

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11
Q

How many cells does each taste bud have?

A

50-150 cells of 4 types

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12
Q

How often is the taste bud receptor turnover?

A

5-10 days

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13
Q

Which types of taste bud cells are taste receptors? basal cells?

A
  • I, II, III = taste receptors
  • IV = basal (develop into new taste receptors)
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14
Q

How many types of taste bud cells are there?

A

4 (I-IV)

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15
Q

According to the slides, which type of taste receptor cell is responsible for salty taste? sour taste? sweet taste? umami taste? bitter taste? water?

A
  • salty = type I
  • sour + water= type III
  • sweet + umami + bitter = type II
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16
Q

According to the notes, what is the mechanism for type I cells?

A
  1. Na+ from salty food enters through a Na+ channel
  2. resulting depolarization opens V-gated Ca2+ channels
  3. influx of Ca2+ causes NT release
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17
Q

Provide an example that demonstrates how insensitive type I cells are.

A

saliva is normally 10 mM NaCl, but for food to taste salty, need >50 mM NaCl

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18
Q

What is the mechanism for type III cells?

A
  1. protons pass through a TRPP3 channel conjoined with a polycystic kidney disease family protein (PKD1L3)
  2. weak acids also pass through lipid membrane
  3. H+ ions close K+ channels –> cell depolarization
  4. open V-gated Na+ channels –> AP
  5. V-gated Ca2+ channels open
  6. 5HT released
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19
Q

What is the general mechanism for type II cells?

A
  1. GPCR senses sweet/umami/bitter
  2. GDP –> GTP-alpha
  3. PLC cleaves PIP2 to IP3
  4. IP3 binds to Ca2+ channel; Ca2+ influx
  5. TRPM5 channel opens
  6. Na++ influx depolarizes the cell
  7. APs generated
20
Q

Which taste receptor proteins make up the sweet type II receptor? Describe the structure. What do they detect?

A
  • heterodimer of T1R2 and T1R3
  • sugars: glucose, fructose, sucrose, aspartame
21
Q

Which taste receptor proteins make up the umami type II receptor? Describe the structure. What do they detect?

A
  • heterodimer of T1R1 and T1R3
  • detect L-glutamate and other L-amino acids
22
Q

Which taste receptor proteins make up the bitter type II receptor? Describe the structure. What do they detect?

A

-dimers of 2 taste receptor proteins from the T2R family

23
Q

How is ATP released when we detect sweet, umami, and bitter?

A
  • Ca2+ that flows in from the type II receptor GPCR not only opens TRPM5 channels, but it also…
  • opens Panx1 channels, releasing ATP into the extracellular space
24
Q

TRUE or FALSE: type I and II taste receptors are ionotropic, whereas type III is metabotropic

A

FALSE: type I and III = ionotropic; type II = metabotropic

25
Q

Explain how type II and type III afferents influence each other.

A
  • ATP released by type II can bind to P2Y receptors (metabotropic) on type II and III cells and P2X receptors (ionotropic) on afferents
  • P2X opening allows influx of Na+ and Ca2+
26
Q

TRUE or FALSE: there are no bitter taste receptors

A

FALSE: there are no spicy taste receptors

27
Q

Where do spicy stimuli bind? What kind of receptors are these?

A
  • bind to free nerve endings
  • thermoreceptors in the tongue, mouth, airway
28
Q

What kind of channels are found on thermoreceptors?

A

TRP channels in free nerve endings in the tongue and mouth

29
Q

What are TRP channels sensitive to?

A

temperature

30
Q

How many transmembrane units make up TRP channels?

A

6

31
Q

What temperature range do warm fibers detect? cold fibers? What is the main TRP channel associated with these fibers?

A
  • warm fibers = above 25 degrees C, TRPV1
  • cold fibers = below 25 degrees C, TRPM8; below 17 degrees C, TRPA1
32
Q

WHat activates TRPV1?

A

capsaicin

33
Q

What acitvates TRPM8?

A

menthol

34
Q

What activates TRPA1?

A

wasabi and cinnamon

35
Q

What behaviours does activation of TRPA1 elicit?

A

tears, airway resistance, cough

36
Q

Explain why wasabi gives a hot sensation even though it activates TRPA1 (which is associated with cold fibers).

A

TRPA1 is often co-expressed with TRPV1 (associated with hot fibers)

37
Q

Which cranial nerves convey taste from the tongue to the brainstem? Which parts of the tongue does each nerve innervate?

A
  • facial VII: anterior 2/3 of tongue
  • glossopharyngeal IX: posterior 1/3 of tongue
  • vagus X: free nerve endings (spicy)
38
Q

To which nucleus in the brainstem do the cranial nerves in the tongue travel? Where does it travel from here?

A

NTS –> VPM of thalamus –> insular cortex –> primary gustatory cortex

39
Q

Which area of the cortex is involved in perception arising from interoceptors (e.g. full bladder, stomach upset)?

A

insular cortex

40
Q

In which area of the cortex is th gustatory cortex found?

A

insular cortex

41
Q

When is the insula activated?

A

during pain and disgust

42
Q

Where does the insula have reciprocal communications?

A
  • secondary somatosensory cortex (S2)
  • amygdala

(hint: food is emotional)

43
Q

Which part of the cortex is associated with value and reward in terms of gustation?

A

orbitorfrontal cortex

44
Q

Which part of the brain is associated with regulating food intake?

A

lateral hypothalamus

45
Q

TRUE or FALSE: olfactory and gustatory integration occurs in the hypothalamus

A

FALSE: in the insular cortex

ZOOL 342 (21 decks)

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