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Neurobiology > Chapter 8: The Chemical Senses > Flashcards

Chapter 8: The Chemical Senses Flashcards

1
Q

What do animals depend on chemical senses to do?

A

Identify nourishment, poison, or potential mate

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2
Q

What are the five types of basic tastes?

A

Saltiness, sourness, sweetness, bitterness, and umami

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3
Q

What chemicals taste sour?

A

Acids

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4
Q

What chemicals taste salty?

A

Salts

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5
Q

What chemicals taste sweet?

A

Sugars like fructose, sucrose, and artifical sweetners

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6
Q

What chemicals taste bitter?

A

Ions like K and Mg, quinine, and caffeine

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7
Q

What do poisonous substances often taste like?

A

Bitter

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8
Q

When you lick a lollipop, which receptors will be activated?

A

Sweet

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9
Q

What other sensory modalities contribute to taste?

A

Temperature, texture, and pain (capsaicin)

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10
Q

What do foliate papillae appear as?

A

Ridges

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11
Q

What do vallate papillae appear as?

A

Pimples

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12
Q

What do fungiform papillae appear as?

A

Mushrooms

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13
Q

What is on the paillae that ranges from 1-hundreds?

A

Taste buds

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14
Q

What is on each taste bud that ranges from 50-150?

A

Taste receptor cells

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15
Q

Threshold Concentration

A

-Just enough exposure of single papilla to selectively detect one taste
-Multiple tastes are detected at higher concentration

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16
Q

What is the taste pore?

A

Opening to expose taste cell to mouth contents

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17
Q

Where is there connectivity in taste cells?

A

-Synpase w/ gustatory afferent axons at the basal end of the taste bud

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18
Q

What is the lifespan of a taste cell?

A

-2 weeks
-Is dependant on connection w/ sensory nerve

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19
Q

Receptor Potential

A

-Voltage shift (depolarization)-may fire action-potentials
-Voltage-gated Na and voltage-gated Ca channels open
-Transmitter released

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20
Q

What is released when sour and salty?

A

Serotonin

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21
Q

What is released from sweet, bitter, umami?

A

ATP

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22
Q

Transduction

A

Process by which an environmental stimulus causes an electrical response in a sensory receptor

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23
Q

What may salt/sour taste stimuli do in transduction?

A

-Pass directly through ion channels

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24
Q

What may sour taste stimuli do in transduction?

A

Binds to and block ion channels

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25
Q

What may bitter/sweet/umami taste stimuli do in transduction?

A

Bind to G-protein-coupled receptors and activate second messenger to open ion channels

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26
Q

Special Na-selective Channel

A

-Normally open
-Increased extracellular Na will cause more Na inward current
—>Depolarization is called receptor potential

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27
Q

[Low] salt tastes good, what happens?

A

Special Na-selective channel

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28
Q

[High] salt tastes bad, what activates?

A

Activate bitter and sour taste cells
—>repellant

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29
Q

What do protons do?

A

Causative agents of acidity and sourness

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30
Q

H can bind and block certain K channels which leands to what?

A

Depolarization

31
Q

H may activate transient receptor potential (TRP) channels, which leads to what?

A

Cation current, which causes depolarization

32
Q

What are the G-protein-coupled taste receptors in bitter, sweet, and umami?

A

T1R and T2R

33
Q

How does the second messengers for bitter, sweet, and umami work?

A
  1. Open Na Channel leads to depolarization
  2. Intracelluler Ca opens, ATP-permeable channel opens, ATP releases, activates postsynpatic purinergic receptors
34
Q

How many types of T2R receptors are there?

A

25

35
Q

Can you tell the difference between 2 bitter tastes?

A

No

36
Q

What sweet receptors are required?

A

T1R2 and T1R3

37
Q

What do the umami receptors do?

A

Detect amino acids
-T1R1 and T1R3

38
Q

What cranial nerves are involved in central taste pathways?

A

-VII Facial: anterior 2/3 of tongue, palate
-IX glossopharyngeal: posterior 1/3 tongue
-X vagus: throat

39
Q

Where do cranial nerves synapse?

A

On gustatory nucelus w/in solitary nucleus in medulla

40
Q

Where do gustaory nucleus axons synapse?

A

On ventral posterior medial (VPM) nucleus in thalamus

41
Q

Where do VPM taste axons synapse?

A

Primary gustatory cortex (mostly ipsilateral to cranial nerves;parietal lobe)

42
Q

Medulla Function

A

Swallowing, salivation, gagging, vomitting, digestion, respiration

43
Q

Hypothalamus

A

Motivation for eating, control of eating based learned cues

44
Q

Amygdala

A

Plasure in eating, control of eating based on learned cues

45
Q

Ageusia

A

Loss of taste perception
-lesions in VPM/gustatory cortex

46
Q

What is the result of localized lesions in the hypothalamus/amygdala?

A

Chronically overeat/ignore food, alter food preferences

47
Q

Labeled line hypothesis

A

Individual taste receptor cells for each stimuli

48
Q

Population coding

A

-Large #s of broadly tuned neurons
-Many taste receptor cells may all synpase w/ the same neuron which results in multiple tastes
-Overall pattern leads to taste
-Contribution of smell, temp., and texture of foods

49
Q

How many smells do we experience?

A

20,000 smells, but only 20% are pleasant

50
Q

Pheromones

A

-Reproductive behavior
-Territorial boundaries
-Identification of individuals
-Signal aggression/submission

51
Q

What is the role of human pheremones?

A

-Unclear
-Synchronization of menstrual cycles
-Mother-baby relationship

52
Q

Olfactory Epithelium

A

-Small, thin sheet of cells high in nasal cavity
1. Olfactory receptor cells-sites of transduction; neurons; last 4-8 weeks
2. Supporting cells-like glia; produce mucus
3. Basal cells-divide to produce new receptor cells

53
Q

Mucus coating is replaced every 10 mintues

A

-Water, mucupolysaccharides, proteins (antibodies, enzymes, odorant binding proteins), salts
-Odorants from sniffing dissolve in the mucus layer before contracting olfactory receptor cells
-Antibodies protect the brain from viruses and bacteria

54
Q

Do humans have weak smellers compared to many animals?

A

Yes

55
Q

What do odorants bind to?

A

Olfactory receptor cilia on dendrite and activate transduction process

56
Q

What do olfactory axons in small clusters do?

A

-Penetrate cribiform plate-thin sheet of bone
-Project to olfactory bulb

57
Q

Anosmia

A

Inability to smell

58
Q

Explain transduction mechanisms of vertebrate olfactory receptor cells

A

-Odorants bind to ordorant receptor proteins
-Activate Golf
-Increase cAMP
-Open cAMO-gated cation channel
-Influx of Na and Ca
-Open Ca -activated Cl channel
-Cl flows our of the cell
-Depolarization leads to receptor potential

59
Q

What ways does termination work?

A

-Diffusion
-Scavenger enzymes in mucus
-Other pathways from cAMP
-Adaptation

60
Q

Adaptation

A

Decreased response of receptor to the smell w/in 1 minute

61
Q

What did Linda Buck and Richard Axel do?

A

In 1991, discovered more than 1000 odorants receptors in rodents’
-Nobel prize in 2004

62
Q

How many receptor types does each receptor cell encode for?

A

1

63
Q

Does each odorant activates only 1 type of receptor?

A

No, it activates many

64
Q

What do olfactory receptor axons project to?

A

Olfactory bulbs

65
Q

How large are glomeruli?

A

50-200 um in diameter

66
Q

25,000 axons converge on dendrites of 100 what?

A

Second-order olfactory neurons

67
Q

What is the orderly map of receptor genes expressed in olfactory epithelium?

A

Map of odor information

68
Q

What are the excitatory and inhibitory connections in the mapping of olfactory receptors neurons?

A

-Glomeruli
-Bulbs

69
Q

Olfactory population coding

A

-Combination of neurons firing distinguishes odor
-Humans can discriminate 1 trillion odors

70
Q

Olfactory maps (sensory maps)

A

-Orderly arrangement of neurons that correlates w/ certain features of the environment
-“Maps” show neurons activated by specific odors

71
Q

What is temporal coding in the olfactory system?

A

-Temporal patterns of spiking in olfactory neurons may encode quality of odors
-Temporal patterns are also clear in spoation odor maps

72
Q

What is anosmia likely arising from in Covid-19?

A

Loss of support cell function instead of the neurons themselves

73
Q

Is sense of smell likely to return in Covid-19 patients?

A

Yes, but soem experience long-term loss and are called long haulers

Neurobiology (8 decks)

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