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Neuroscience > Lecture 16 > Flashcards

Lecture 16 Flashcards

1
Q

What are the functions of the chemical senses?

A

Identify food sources
Avoid noxious substances
Find a mate or make territories

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2
Q

How are chemical senses achieved?

A

By the gustatory system and the olfactory system

  • Have separate transduction mechanisms
  • Information is processed in parallel
  • Information is merged in the CNS
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3
Q

What are the five basic tastes?

A

Salty
- vital electrodes, ionotropic
Sour
- acids, H, ionotropic (fatty acids etc)
Sweet
- innate fondness, high energy foods, metabotropic (GPCRs)
Bitter
- instinctively rejected, often poisons, metabotropic
Umami
- savory taste of glutamate, metabotropic

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4
Q

How do we perceive all of the flavors of food?

A

Likely other tastes and receptors e.g. fat, starch
Deficits in nutrients can lead to cravings
Combination of taste, smell and touch (texture) are combined in the cortex

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5
Q

What is the function of the Lingual papillae?

A

Taste-sensing structure

Taste organs = primarily tongue, also cheeks, soft palate, pharynx, epiglottis

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6
Q

What are the four types of lingual papillae?

A

Filiform
- spiked, no taste buds, sense texture, most abundant
Foliate
- ridges, least abundant, gone by 2-3 years
Fungiform
- mushrooms, mainly at sides and front
Circumvallate
- pimples, large, contain about half of all taste buds

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7
Q

What do taste buds contain?

A

Taste cells and gustatory afferents

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8
Q

How many taste buds are there in total?

A

2000-5000

- Different range of sensitivity may depend on number of taste buds in individual

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9
Q

How many taste cells are there per taste bud?

A

100

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10
Q

What is the function of taste pores?

A

Stimulus detection by microvilli

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11
Q

What type of receptors are taste cells?

A

chemoreceptors

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12
Q

What do gustatory afferents do?

A

Carry information to CNS

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13
Q

What type of tastes are GPCRs used for?

A

Bitterness, sweetness and umami

- similar transduction mechanism to other cells

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14
Q

What is TrpM5?

A

Ion channel opens to allow other cations in cell (Na, Ca)

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15
Q

What is VGNC?

A

Causes second depolarization (depolarization size depends on stimulus size)

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16
Q

Do GPCRs for taste use synaptic vesicles?

A

no

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17
Q

What activates GPCRs at the end?

A

Na

18
Q

What is used as a neurotransmitter for GPCRs for taste?

A

ATP

- activates neurons

19
Q

What are VGNC activated by?

A

Activated for sourness (alongside VGCC)

  • more like a traditional synapse
  • activates synaptic vesicles
  • variety of neurotransmitters
20
Q

Do taste cells have the same thresholds for different basic tastes?

A

No; they are different

21
Q

How does a taste cell respond to different tastes?

A

e.g. can respond to sweet and salty stimuli but will respond best to one of these stimuli, as it will be detected at a lower threshold

22
Q

Why can we not have a completely specific labelled line code?

A

Because every flavor 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)

23
Q

Where do the gustatory afferents from anterior 2/3 of the tongue carry signals?

A

Facial nerve (cranial nerve VII)

24
Q

What is the site of odorant detection?

A

Olfactory epithelium

25
Q

How are odorants detected?

A

Detected as low as a few parts per trillion

Must dissolve in the mucus layer to reach olfactory receptor cells

26
Q

How big is the human olfactory epithelium compared to the dog olfactory epithelium?

A

Human: 10cm2
Dog: 170 cm2
Dogs have 100 times more receptors per cm2

27
Q

What type of neurons are olfactory receptor cells?

A

Chemoreceptive neurons

28
Q

Where is transduction machinery found within?

A

Cilia at the end of the dendrite

29
Q

What is the primary afferent neuron?

A

the axon of the olfactory receptor cell

30
Q

What is the structure of axons of the olfactory receptor cell?

A

Thin, unmyelinated and form the olfactory nerve (cranial nerve I)

31
Q

What are one of the few types of neurons that are regularly replaced in adults?

A

Olfactory receptor cells

32
Q

How many odorant receptor proteins are there in humans?

A

350

33
Q

What type of receptors are odorant receptor proteins?

A

GPCRs

34
Q

Does every odorant receptor protein use the same downstream pathway?

A

Yes

35
Q

How much of the genome do odorant receptor protein genes comprise?

A

3-5%

36
Q

What type of mice are anosmic (cannot smell)?

A

Golf knockout mouse

37
Q

What opens cyclic nucleotide channel to let in Na and Ca for depolarization?

A

cAMP

38
Q

What is the function of ANO2?

A

Allows Cl into and out of the cell

  • Cl must move out of the cell and not in like other cells
  • cilia already have a higher concentration of Cl already so Cl moves down concentration
39
Q

What can large enough receptor potentials lead to?

A

Reach threshold for action potential firing

40
Q

What can an intense stimulus lead to?

A

Large receptor potential = increased action potential firing rate

41
Q

Where does the glomeruli of the olfactory bulb input from?

A

Specific olfactory receptor cells

  • each glomeruli is associated with a certain type of receptor cell
  • second order neurons carry information from glomeruli to various regions of the brain

Neuroscience (28 decks)

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