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BIOL 404 FINAL > Taste > Flashcards

Taste Flashcards

1
Q

taste buds contain ___ taste cells

A

50-100

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2
Q

the 5 taste modalities are…

A

fat, umami, salt, bitter, sour and sweet

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3
Q

we have ____ taste buds

A

~5000

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4
Q

taste cells contain ___ which house ____

A

microvilli, taste receptors

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5
Q

label this diagram:

A

a: sensory neuron
b: nerve fiber
c: microvilli containing taste receptors

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6
Q

where are taste buds?

A

in 3 kinds of papillae (folds) in the tongue

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7
Q

what are the 3 kinds of papillae?

A

Fungiform, foliate, circumvallate

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8
Q

describe fungiform

A
  • 250; each contain 1-5 taste buds
  • Simplest; have microvilli on the surface
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9
Q

describe foliate

A

20; each contain 100-50 taste buds, small invagination

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10
Q

describe circumvallate

A

8-10; each contain 250 taste buds
- account for half of the total taste buds.
- Near the back of the tongue.
- Contain deep grooves where saliva can enter and expose tastants to taste buds.

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11
Q

taste cells have a lifespan of _____; they regenerate due to being exposed to the _____

A

1 week, environment

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12
Q

label this diagram:

A

a: circumvallate
b: foliate
c: fungiform

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13
Q

taste cells form ____ based on what ___ they reside in

A

afferents, papillae

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14
Q

What cranial nerves do fungiform, foliate, circumvallate, and epiglottic taste receptors contribute to?

A

Fungiform: CN VII
Foliate: CN IX and CN VII
Circumvallate: CN IX
Epiglottic: CN X

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15
Q

What ganglion cells constitute the Facial Nerve (CN VII)

A

geniculate ganglion cells.

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16
Q

what nerves innervate facial nerve CN VII?

A

It is innervated by the greater petrosal and chorda tympani nerves

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17
Q

where does facial nerve CN VII collect sensory info from?

A

the anterior ⅔ of the tongue.

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18
Q

What ganglion cells constitute the Glossopharyngeal Nerve (CN IX)?

A

inferior ganglion cells.

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19
Q

what innervates glossopharyngeal nerve CN IX?

A

pestrosal ganglion cells

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20
Q

where does glossopharyngeal nerve CN IX collected sensory info from?

A

from the posterior ⅓ of the tongue.

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21
Q

what ganglion cells constitute the vagus nerve CN X?

A

inferior/nodose ganglion cells

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22
Q

where does vagus nerve collect sensory info from?

A

the epiglottis

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23
Q

Where do all taste nerves terminate?

A

in the rostral part of the nucleus of the solitary tract.

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24
Q

from the nucleus of the solitary tract, second order neurons of the cranial nerves project to

A

ventral posteriormedial nucleus of the thalamus

25
Q

second order neurons also participate in ________ through projections to the ______.

A

reflex pathways involved in salivation, swallowing, and coughing, dorsal motor nucleus of the vagus (DMNX).

26
Q

After the thalamus, where do the central taste pathways continue?

A

the taste pathways go to the frontal cortices (gustatory cortex) and then to the amygdala (fear center).

27
Q

Apart from thalamus and amygdala, where else does the nucleus of the solitary tract project to?

A

the hypothalamus

28
Q

Describe the nature of the taste pathway from the tongue to the nucleus of the solitary tract.

A

is ipsilateral and uncrossed.

29
Q

Which channels detect salty tastes?

A

Amiloride-sensitive ENaCs.

30
Q

What drives the activation of amiloride-sensitive ENaCs in salty taste detection?

A

Activation is driven by the Nernst potential based on the salt concentration in saliva.

31
Q

What channels detect acidic tastes?

A

H+-sensitive TRP channels.

32
Q

What influences the activation of H+-sensitive TRP channels in acidic taste detection?

A

Activation is influenced by the concentration of protons in saliva.

33
Q

Which taste sensations do GPCRs detect?

A

GPCRs detect sweet, umami, and bitter tastes.

34
Q

Name the subunits responsible for sweet taste detection by GPCRs.

A

T1R2, T1R3.

35
Q

Name the subunits responsible for umami taste detection by GPCRs.

A

T1R1, T1R3.

36
Q

name the subunits responsible for bitter taste detection by GPCRs.

A

T2RX

37
Q

What occurs upon activation of a GPCR?

A

The GPCR promotes the exchange of GDP for GTP on the alpha subunit of the G-protein.

38
Q

What happens after GPCR activation regarding the alpha subunit (Gustducin)?

A

The alpha subunit dissociates from the beta and gamma subunits.

39
Q

What does the dissociated alpha subunit (Gustducin) do in the GPCR pathway?

A

The alpha subunit activates phospholipase C.

40
Q

What is the role of phospholipase C in the GPCR pathway?

A

Phospholipase C catalyzes the conversion of PIP2 into DAG and IP3.

41
Q

What happens with IP3 in the endoplasmic reticulum in the GPCR pathway?

A

IP3 binds and liberates Ca2+.

42
Q

What does Ca2+ liberated by IP3 in the endoplasmic reticulum do in the GPCR pathway?

A

Ca2+ binds to and activates TRP channels, allowing for more Ca2+ influx.

43
Q

How is the GPCR transduction pathway differentiated for sweet, umami, and bitter tastes?

A

Depending on taste (sweet, umami, or bitter), different receptors and specialized G proteins are involved.

44
Q

Is it likely that each taste bud recognizes only a single tastant?

A

No, it is unlikely; instead, there are multiple types of taste cells within a single taste bud.

45
Q

What is the function of Type I TBC in taste buds?

A

Involved in detecting salt; has specialized K+ leak channels for extruding intracellular K+ to the apical surface.

46
Q

What tastes does Type II TBC detect, and how does it release signals?

A

Detects sweet, umami, and bitter tastes; releases ATP upon depolarization, interacting with P2X and P2Y afferents for postsynaptic cell activation.

47
Q

What is the ATP channel on the presynaptic cell, and what happens in knockouts?

A

Panx1; knockouts do not prevent ATP release

48
Q

Name the channels involved in mediating ATP release by Type II TBC.

A

CALHM1/CALHM3; channels permeable to Ca2+, mediating ATP release (KO results in no ATP release).

49
Q

What is the function of Type III TBC in taste buds?

A

Involved in detecting sour taste; releases serotonergic vesicles activating downstream afferents and inhibiting neighboring cells for taste discrimination.

50
Q

How does Type III TBC allow for discrimination between tastes?

A

Releases serotonergic vesicles activating downstream afferents but inhibiting neighboring cells for discrimination between tastes.

51
Q

What is the purpose of Two-Photon Microendoscopy?

A

Used to view living neurons at depths unachievable by other techniques.

52
Q

How does Two-Photon Microendoscopy measure the activity of geniculate ganglion cells?

A

Measures calcium expression using a fluorescent indicator, changing color upon calcium binding, indicating neuronal activity.

53
Q

What was observed regarding the activation of geniculate ganglion cells in response to tastants?

A

Neurons are selectively activated by different tastants, and some respond to multitastants, but most are tuned to a single modality.

54
Q

Is there a map in the gustatory cortex, and what does it represent?

A

Yes, there is a gustotopic map representing different tastants in different areas.

55
Q

Why is optogenetic control used in experiments related to gustatory perception in mice?

A

To determine if the mouse perceives a tastant due to the activation of specific areas in the gustatory cortex rather than a higher-up process.

56
Q

Describe the experimental setup involving two chambers in optogenetic control.

A

Mice are placed in two chambers, one with light stimulation and one without. Responses, like sweet or bitter reactions, are observed based on light stimulation.

57
Q

What behavioral responses were observed when light stimulation elicited a sweet or bitter response?

A

When light elicited a sweet response, the mouse spent more time in the stimulated chamber. When it elicited a bitter response, the mouse spent less time there.

58
Q

How were mice trained in experiments involving licking water in response to light?

A

Mice were trained to lick water in response to a tone. Thirsty mice, upon hearing a tone, start licking the water spout.

59
Q

What does the light stimulation indicate in mice trained to lick water, and what behavioral response is observed for bitter-tasting water?

A

Light stimulation indicates if the water is bitter or sweet. If bitter, the mouse stops licking, even in TRPM5 knockout mice, suggesting an innate behavior.

BIOL 404 FINAL (8 decks)

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