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BS357: Introduction to Neuroscience I > Chapter 8: The Chemical Senses > Flashcards

Chapter 8: The Chemical Senses Flashcards

1
Q

2 chemical senses

A
  1. gustation
  2. olfaction
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2
Q

5 major tastes: () – common among many different cultures (box 8.1)

A

Saltiness, sourness, sweetness, bitterness, and umami (MSG)

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3
Q

Poisonous substances—often () -> taste senses offer advantage for survival

A

bitter

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4
Q

factors that contribute to distinguishing countless flavors of food

A
  • activation of different combinations of taste receptors
  • distinctive smell
  • other sensory modalities: texture, temperature
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5
Q

Areas of sensitivity on the tongue: sweetness

A

tip of the tongue

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6
Q

Areas of sensitivity on the tongue: bitterness

A

back of the tongue

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7
Q

Areas of sensitivity on the tongue: saltiness and sourness

A

sides of the tongue

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8
Q

small structures on the upper surface of the tongue that give it its characteristic rough texture

A

papillae

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9
Q

3 different shapes of papillae

A
  1. foliate - back part of sides of tongue
  2. vallate - back part of tongue
  3. fungiform - front and middle part of tongue
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10
Q

major origin of taste sense

A

taste buds

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11
Q

taste buds consist of several ()

A

taste cells

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12
Q

taste cells form chemical and electrical synapses with (1) and (2)

A
  1. gustatory afferent axons
  2. basal cells
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13
Q

() are found at the base of taste buds

A

basal cells

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14
Q

() bring sensory information from the tongue to dorsal root ganglia

A

gustatory afferent axons

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15
Q

sensory neuron don’t have ()

A

dendrites

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16
Q

At the apical ends of taste buds, taste cells form (1) -> together form (2), which directly interacts with chemicals

A
  1. microvilli
  2. taste pore
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17
Q

Taste receptor cell membrane potential is usually changed by depolarization, which triggers () that are delivered to gustatory ANs

A

receptor potentials

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18
Q

Most taste receptor cells respond primarily to ().

A

just one of basic tastes

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19
Q

taste stimuli

A

tastants

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20
Q

transduction processes for tastants

A
  1. Pass directly through ion channels
  2. Bind to and block ion channels
  3. Bind to G-protein-coupled receptors and activate second messengers to open ion channels
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21
Q

Tastants open or block ion channels to () taste cell membranes

A

depolarize

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22
Q

If sodium arrives to surface of salt-sensitive taste cells, they pass directly through the (1)

A
  1. selective Na+ channels
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23
Q

the selective Na+ channels in salt-sensitive taste cells can be blocked by (1), thus they are also called (2)

A
  1. amiloride
  2. amiloride-sensitive Na+ channels
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24
Q

the NT released by synaptic vessels in salt and sour-sensitive taste cells is (); this binds to gustatory axon terminals to deliver signal to CNS

A

serotonin

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25
Q

(): causative agents of acidity and sourness

A

Protons

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26
Q

Sourness originates from (1)—>(2)

A
  1. high acidity
  2. low pH
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27
Q

Protons directly penetrate the () (usually open in sour-sensitive taste cell) to cause H+ influx -> depolarization

A

H+ channel

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28
Q

3 tastes that share common mechanism of signal transduction

A

bitterness, sweetness, umami

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29
Q

the 2 families of taste receptor proteins involved in signal transduction for bitterness, sweetness, umami

A

T1R and T2R

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30
Q

receptors involved in bitterness, sweetness, umami are all ()

A

GPCRs

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31
Q

proteins that make up the bitter receptors

A

homodimer of T2R receptors

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32
Q

proteins that make up sweet receptors

A

heterodimer of T1R2 and T1R3

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33
Q

proteins that make up the umami receptors

A

heterodimer of T1R1 and T1R3

34
Q

ligand of umami receptors

A

amino acids (proteins)

35
Q

portion of the thalamus that deals with sensory information in the head

A

ventral posterior medial (VPM) nucleus

36
Q

cranial nerves (VII, IX, and X) carry () and deliver taste info to the brain

A

primary gustatory axons

37
Q

taste axons of cranial nerves involved in gustation all enter the brain stem, bundle together, and synapse within the ()

A

gustatory nucleus

38
Q

the VPM is synapsed by neurons of the ()

A

gustatory nucleus

39
Q

after receiving signals from the gustatory nucleus, the VPM delivers the signal to the () in the medulla

A

primary gustatory cortex

40
Q

() - loss of taste perception

A

Ageusia

41
Q

summary of central taste pathways

A

Cranial nerves—>gustatory nucleus—>primary gustatory cortex (located in cerebral cortex)

42
Q

ageusia can be caused by () in the VPM, thalamus, or gustatory cortex

A

localized lesions

43
Q

states that individual taste receptor cells for each stimuli

A

labeled line hypothesis

44
Q

involves coordination of large number of broadly tuned neurons -> convergence of receptor cell input onto afferent axons

A

population coding

45
Q

Because population coding takes into account information from other neurons, it may explain the contribution of () to one’s perception of food

A

texture, temperature, smell

46
Q

() in response to a taste/food are distinctly different

A

overall patterns of discharge (APs)

47
Q

how do we distinguish between tastes (salt vs sour, bitter vs sweet vs umami)

A

each taste cell selectively expresses only 1 class of taste receptor proteins

48
Q

chemicals released by the body that are important signals for reproductive behavior, territorial boundaries, identification of individuals, etc. in animals but have weak role in humans

A

pheromones

49
Q

major organ for sensing smell

A

olfactory epithelium

50
Q

3 types of cells in the olfactory epithelium

A
  1. olfactory receptor cells
  2. supporting cells
  3. basal cells
51
Q

type of cell in olfactory epithelium: sites of transduction; one of the few types of neurons in the nervous system that are regularly replaced throughout life

A

olfactory receptor cells

52
Q

type of cell in olfactory epithelium: similar to glia; help produce mucus (produces and maintains mucus layer)

A

supporting cells

53
Q

why are antibodies important in the mucus layer of the olfactory epithelium

A

because epithelium is directly exposed to outside (viruses, bacteria, etc.)

54
Q

proteins in olfactory epithelium mucus layer that help concentrate odorants in nucleus

A

odorant-binding proteins

55
Q

bone that allows innervation of olfactory epithelium by olfactory nerve axons

A

Cribriform plate

56
Q

activate transduction processes in olfactory neurons

A

odorants

57
Q

inability to smell

A

anosmia

58
Q

why do humans have a weak sense of smell

A

Due to small surface area of olfactory epithelium

59
Q

Ways to terminate Olfactory response

A
  1. Odorants diffuse away
  2. breakdown of odorants by scavenger enzymes in mucus
  3. cAMP in receptor cell may activate other signaling pathways that end transduction process
60
Q

2 unusual features of olfactory signaling

A
  1. receptor binding proteins at the beginning
  2. cAMP-gated channels near the end
61
Q

collectively, the olfactory axons constitute the ()

A

olfactory nerve (cranial nerve I)

62
Q

small clusters of olfactory axons penetrate the cribriform plate then course into the ()

A

olfactory bulb

63
Q

in olfactory cells, () is unusually high

A

intracellular [Cl-]

64
Q

Different odorants are recognized by ()

A

different receptor proteins

65
Q

Increasing evidence indicates that the only second messenger mediating olfactory transduction in vertebrates is ()

A

cAMP

66
Q

in most cases, only () is expressed in 1 olfactory receptor cell

A

1 type of receptor protein

67
Q

olfactory receptor proteins belong to the () family

A

G protein-coupled receptor

68
Q

G protein in olfactory receptor cells

A

G_olf

69
Q

like taste, olfaction involves a () scheme to distinguish between smells

A

population-coding

70
Q

Small spherical structures located in the input layer of olfactory bulbs; spherical forms of axon terminals

A

glomeruli (glomerulus)

71
Q

each glomerulus contains endings of about 25k (1) that converge and terminate on the dendrites of about 100 (2)

A
  1. primary olfactory axons
  2. second-order olfactory neurons
72
Q

Each glomerulus receives input from receptor cells of only ()

A

1 type

73
Q

() -> molecular labeling method used to visualize mapping of receptor cells onto glomeruli

A

P2::LacZ knock-mouse

74
Q

output axons of the olfactory bulbs connect directly to several targets, most notably the () (located in primitive region of the cerebral cortex) and some of its neighboring structures in the temporal lobes

A

olfactory cortex

75
Q

Conscious perception of smell may be mediated by the ff path:

A

olfactory tubercle -> medial dorsal nucleus (of thalamus) -> orbitofrontal cortex

76
Q

orderly arrangement of neurons that correlates with certain features of the environment

A

sensory map

77
Q

while a particular odor activated many bulb neurons, the neuron’s positions form ()

A

complex but reproducible spatial patterns

78
Q

the most critical feature of each odorant is its ()

A

chemical structure

79
Q

each distinct odor triggers activity in ()

A

a different subset of neurons

80
Q

depends on the timing of AP spikes, might encode the quality of odors

A

temporal coding

BS357: Introduction to Neuroscience I (13 decks)

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