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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
What may bitter/sweet/umami taste stimuli do in transduction?
Bind to G-protein-coupled receptors and activate second messenger to open ion channels
26
Special Na-selective Channel
-Normally open -Increased extracellular Na will cause more Na inward current —>Depolarization is called receptor potential
27
[Low] salt tastes good, what happens?
Special Na-selective channel
28
[High] salt tastes bad, what activates?
Activate bitter and sour taste cells —>repellant
29
What do protons do?
Causative agents of acidity and sourness
30
H can bind and block certain K channels which leands to what?
Depolarization
31
H may activate transient receptor potential (TRP) channels, which leads to what?
Cation current, which causes depolarization
32
What are the G-protein-coupled taste receptors in bitter, sweet, and umami?
T1R and T2R
33
How does the second messengers for bitter, sweet, and umami work?
1. Open Na Channel leads to depolarization 2. Intracelluler Ca opens, ATP-permeable channel opens, ATP releases, activates postsynpatic purinergic receptors
34
How many types of T2R receptors are there?
25
35
Can you tell the difference between 2 bitter tastes?
No
36
What sweet receptors are required?
T1R2 and T1R3
37
What do the umami receptors do?
Detect amino acids -T1R1 and T1R3
38
What cranial nerves are involved in central taste pathways?
-VII Facial: anterior 2/3 of tongue, palate -IX glossopharyngeal: posterior 1/3 tongue -X vagus: throat
39
Where do cranial nerves synapse?
On gustatory nucelus w/in solitary nucleus in medulla
40
Where do gustaory nucleus axons synapse?
On ventral posterior medial (VPM) nucleus in thalamus
41
Where do VPM taste axons synapse?
Primary gustatory cortex (mostly ipsilateral to cranial nerves;parietal lobe)
42
Medulla Function
Swallowing, salivation, gagging, vomitting, digestion, respiration
43
Hypothalamus
Motivation for eating, control of eating based learned cues
44
Amygdala
Plasure in eating, control of eating based on learned cues
45
Ageusia
Loss of taste perception -lesions in VPM/gustatory cortex
46
What is the result of localized lesions in the hypothalamus/amygdala?
Chronically overeat/ignore food, alter food preferences
47
Labeled line hypothesis
Individual taste receptor cells for each stimuli
48
Population coding
-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
How many smells do we experience?
20,000 smells, but only 20% are pleasant
50
Pheromones
-Reproductive behavior -Territorial boundaries -Identification of individuals -Signal aggression/submission
51
What is the role of human pheremones?
-Unclear -Synchronization of menstrual cycles -Mother-baby relationship
52
Olfactory Epithelium
-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
Mucus coating is replaced every 10 mintues
-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
Do humans have weak smellers compared to many animals?
Yes
55
What do odorants bind to?
Olfactory receptor cilia on dendrite and activate transduction process
56
What do olfactory axons in small clusters do?
-Penetrate cribiform plate-thin sheet of bone -Project to olfactory bulb
57
Anosmia
Inability to smell
58
Explain transduction mechanisms of vertebrate olfactory receptor cells
-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
What ways does termination work?
-Diffusion -Scavenger enzymes in mucus -Other pathways from cAMP -Adaptation
60
Adaptation
Decreased response of receptor to the smell w/in 1 minute
61
What did Linda Buck and Richard Axel do?
In 1991, discovered more than 1000 odorants receptors in rodents’ -Nobel prize in 2004
62
How many receptor types does each receptor cell encode for?
1
63
Does each odorant activates only 1 type of receptor?
No, it activates many
64
What do olfactory receptor axons project to?
Olfactory bulbs
65
How large are glomeruli?
50-200 um in diameter
66
25,000 axons converge on dendrites of 100 what?
Second-order olfactory neurons
67
What is the orderly map of receptor genes expressed in olfactory epithelium?
Map of odor information
68
What are the excitatory and inhibitory connections in the mapping of olfactory receptors neurons?
-Glomeruli -Bulbs
69
Olfactory population coding
-Combination of neurons firing distinguishes odor -Humans can discriminate 1 trillion odors
70
Olfactory maps (sensory maps)
-Orderly arrangement of neurons that correlates w/ certain features of the environment -“Maps” show neurons activated by specific odors
71
What is temporal coding in the olfactory system?
-Temporal patterns of spiking in olfactory neurons may encode quality of odors -Temporal patterns are also clear in spoation odor maps
72
What is anosmia likely arising from in Covid-19?
Loss of support cell function instead of the neurons themselves
73
Is sense of smell likely to return in Covid-19 patients?
Yes, but soem experience long-term loss and are called long haulers

Neurobiology (8 decks)

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