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Neuroscience Exam 2: Nastassia > Lecture 1: Chemical Senses: Olfaction & Gustation > Flashcards

Lecture 1: Chemical Senses: Olfaction & Gustation Flashcards

1
Q

How much olfactory stimuli can humans discriminate?

A

over 1 trillion

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2
Q

Where are olfactory cells located?

A

in the epithelium of the nose

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3
Q

What are the physical characteristics of olfactory receptor neurons?

A
  • simple cells
  • bipolar
  • Dendrites form the cilia
  • Axons terminate in olfactory bulb
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4
Q

What type of molecules do odorants tend to be?

A

Small volatile molecules that are lipid soluble

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5
Q

~400-500 genes in the human genome code for how many olfactory receptors?

A

~1000

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6
Q

Odor receptors have how many transmembrane domains?

A

7

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7
Q

Odor receptors classify as what type of receptor?

A

G protein coupled-receptor (GPCR)

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8
Q

Odor receptors detect odorants based on what? (4)

A
  • size
  • charge
  • amino acid group
  • vibration of C-H groups
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9
Q

Where is the binding site of odor receptors located?

A

on extracellular terminus

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10
Q

Each neuron has _____ type of receptor, but can respond to more than one __________.

A

one, odorant

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11
Q

A single odor receptor may respond to ___________ or ________odorants

A

Single, Multiple

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12
Q

What is the 1st route of activation of the release of the olfactory G-protein (GOLF)?

A
  1. activates adenylate cyclase -> produces cAMP
  2. cyclic nucleotide gated channel (CNGA) opens -> Na+/Ca2+ influx (depolarization)
  3. Ca2+ activates Cl- channel -> Cl- efflux (further depolarization)
  4. Depolarization triggers action potentials
  5. Ca2+ levels are restored by exchangers (Na+/Ca2= exchanger) and pumps
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13
Q

What are the steps involved in the reduction in ordorant sensitivity/olfactory adaptation?

A
  1. all steps from 1st route of activation of GOLF
  2. inititial adaptation occurs when increased Ca2+ binds to Ca2+ binding protein that desensitizes CNGA channel
  3. short term adaptation occurs by increased desensitization via Ca2+ calmodulin protein kinase 2 acting on adenylyl cyclase
  4. long term adaptation occurs downstream of Ca2+ mediated nitric oxide production -> stimulates guanylate cyclase to produce cGMP and causes Ca2+ influx through CNGA channe; leading to desensitization of CNGA and adenylyl cyclase
  5. an Na+/Ca2+ exchanger restores ionic balance
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14
Q

What is the 2nd route of olfactory receptor via release of GOLF?

A
  1. activates phospholipase C (PLC)-IP3 pathway -> opens Ca2+ channel
  2. Ca2+ channel causes desensitization
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15
Q

What occurs during Olfactory Adaptation?

A

Reduction in odorant sensitivity

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16
Q

Explain the Initial Adaptation that occurs during olfactory adaptation

A

Occurs when increased Ca2+ binds to cbp (Ca2+ binding protein) that desensitizes the CNGA channel

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17
Q

Explain the Short-term Adaptation that occurs during olfactory adaptation

A

Occurs by increased desensitization of Ca2+ calmodulin protein kinase II acting on AC (adenylase cyclase) which decreases the production on cAMP

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18
Q

Explain the Long-term Adaptation that occurs during olfactory adaptation

A
  • Occurs downstream of Ca2+ mediated nitric oxide production which stimulates guanylate cyclase to produce cGMP (cG)
  • cGMP causes persisent Ca2+ influx through CNGA channel. leading to further desensitization of CNGA and AC
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19
Q

What is the purpose of the vomeronasal organ in non-ape mammals?

A

mediate activation by pheromones

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20
Q

What organ is considered a high specialist receptor?

A

vomeronasal

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21
Q

What are the characteristics of the 2nd group (TAARs) of chemosensors in olfactory epithelium?

TAARs: Trace-Amine-Associated Receptors

A
  • found in all mammals
  • highly selective for specific pheromones
  • highly sensitive
  • used GOLF/cAMP signal transduction mechanisms
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22
Q

What is a glomerulus?

A

axon of the olfactory receptor neurons in the glomeruli of olfactory bulb

~2000 glomeruli in mammals

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23
Q

Each glomerulus receives info from what?

A

only one type of olfactory receptor neuron

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24
Q

Each glomerulus receives thousands of olfactory receptor neuron axons which synapse with what?

A

20-50 relay neurons (mitral/tufted)

Similar/identical OR (odordant receptor) to the same glomerulus

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25
Q

Where does info from the PNS enter the CNS?

A

glomerulus

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26
Q

What are the 5 layers of the olfactory bulb?

A
  1. olfactory receptor nerves
  2. odorant-specific glomeruli (synapses)
  3. external plexiform layer
  4. mitral cell layer
  5. granule cell layer
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27
Q

Tufted/mitral cells receive info from …. and relay info to ….

A

olfactory sensory neurons in the glomerulus; olfactory tract (CNS)

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28
Q

What is the purpose of parallel projection involved in lateral inhibition?

A

increases odor discrimination (both @ glomeruli and mitral/tufted)

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29
Q

What is an example of lateral inhibition?

A

if green has a large activation and blue has partial, green will shut down blue and only green will be presented

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30
Q

What cranial nerve does olfactory projection go through?

A

Cranial nerve I (Olfactory nerve)

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31
Q

Mitral cells send info to how many different regions?

A

5, Info goes through lateral olfactory tract then to either:

  • anterior olfactory nucleus
  • olfactory tubercle
  • piriform cortex
  • amygdala
  • entorhinal cortex
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32
Q

Where do tufted cells send info to?

A
  • anterior olfactory nucleus
  • olfactory tubercle
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33
Q

What pathway is responsible for odor perception and discrimination?

A

thalamus to the orbitofrontal cortex

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34
Q

Pathways to the amygdala and hypothalamus regulate what?

A
  • emotional/motivational aspects for smell
  • physiological/behavioral aspects of odors
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35
Q

Odor induced fear signaling is located in what boundary?

A

amygdala-piriform

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36
Q

What cortex lacks structure/organization?

A

piriform

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37
Q

At what age do humans begin to lose the smelling of pleasant odors?

Olfactory Senescence

A

36

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38
Q

How is olfaction related to Idiopathic Parkinson’s Disease?

A
  • show more loss of smell than vascular Parkinson’s
  • tend to be anosmic
39
Q

How is olfaction related to Huntington’s Chorea?

A

shows intermediate amount of loss

40
Q

How is olfaction related to Alzeheimer’s Disease?

A

have olfactory impairment that may begin centrally

41
Q

SARS-Cov-2 likely infects what cells to express what?

A

support cells in olfactory epithelium -> epxress ACE2

42
Q

Where are taste cells located?

A
  • tongue
  • pharynx
  • palate
  • epiglottis
  • upper third of esophagus
43
Q

The gustatory system is innervated by what nerves?

A
  • CN 7-Facial
  • CN 9-Glossopharyngeal
  • CN 10-Vagus
44
Q

What are the characteristics (name and innervation) of cranial nerve 7?

A
  • innervates the tongue
  • Facial (chorda tymphani branch) via geniculate ganglion
45
Q

What are the characteristics (name and innervation) of cranial nerve 9?

A
  • innvervates the tongue
  • Glossopharyngeal (lingual branch) via petrosal ganglion
46
Q

What are the characteristcs (name and innervation) of cranial nerve 10?

A
  • innvervates the pharynx and esophagus
  • Vagal (superior laryngeal branch) via nodose ganglion
47
Q

Taste buds on the tongue are embedded in what?

A

papillae

48
Q

What is located at the anterior 2/3 portion of the tongue?And what innervates it?

A
  • fungiform and filliform papillae
  • Innervated by the facial nerve (CN VII)
49
Q

What is located at the posterior portion of the tongue? And what innervates it?

A
  • Circumvallate and foliate papillae
  • Innervated by the glossopharyngeal nerve (CNIX)
50
Q

How many taste buds are on the human tongue?

A

4000

51
Q

What occurs at the apical end of the tongue?

A

microvilli contact the tastant which is dissolved in saliva and taste pore mucus

52
Q

How often does the turnover of taste cells occur?

A

every 10 days

53
Q

What are the tastants?

A
  • sweet -> sucrose (threshold 20 mM)
  • salty -> NaCl (threshold 10 mM)
  • sour -> citric acid (threshold 2 mM)
  • bitter -> quinine (threshold 8 𝜐M)
  • umami -> glutamate (meaty flavor) (threshold 100 𝜐M)
  • water
54
Q

What are the 4 types of taste cells?

A
  • type I
  • Type II
  • Type II
  • B cells
55
Q

What is the purpose of type 1 taste cells?

A

have support function -> putative salt sensor

56
Q

What are the characteristics of type 2 taste cells?

A
  • large cells that have GPCRs for bitter, sweet, and umami
  • associate with different afferent nerve fibers
  • DO NOT form conventional synapses
57
Q

What are the characteristics of type 3 taste cells?

A
  • respond to sour stimuli
  • form prominent synapses with afferent nerve fibers
  • vesicular relase of serotonin and ATP
  • HAVE conventional synapses
58
Q

What type of cells are B cells?

A

progenitor cells

59
Q

What is the numerical distribution of the taste cells?

A

type 1> type 2> type 3

60
Q

What is the taste receptor associated with umami?

A

T1R1 + T1R3

61
Q

What is the taste receptor associated with sweet?

A

T1R2 + T1R3

62
Q

What is the taste receptor associated with bitter?

A

-30 T2Rs

63
Q

What is the taste receptor associated with sodium?

A

ENaC

64
Q

What is the taste receptor associated with sour?

A
  • PKD2L1 for acids
  • CA IV for carbonated drinks
65
Q

What are the steps involved in type 2 signal transduction for taste?

A
  1. ggustucin is stimulated -> phospholipase B2 is activated
  2. hydrolysis of B2 into IP3 and diacylglycerol
  3. IP3 causes Ca2+ release at ER
  4. TRPM5 is activated -> causes Na+ rush -> depolarization of cells -> burst of action potentials
  5. depolarization activates CALHM1 -> allows ATP to flow out and activate nerve
66
Q

High sensitivity of ENaC (salt) is responsible for what?

A

salt attraction (lower conc. of salt)

67
Q

Low sensitivity for ENaC (salt) is responsible for what?

A

salt aversion (high conc. of salt)

68
Q

High sensitivity for salt occurs in what type of cells?

A

Type 1

69
Q

Low sensitivity for salt occurs in what type of cells?

A

Type 2

70
Q

For high sensitivity, what is ENaC inhibited by?

A

amiloride

71
Q

How does citric acid induce cation influx?

A

via PKD heteromer

72
Q

How can sour sensing be reduced?

A

PKD knockout

73
Q

During the communication between taste cells and afferent nerves, what do ggustucin fibers express?

A

P2X2/3 (ATP sensitive ion channel)

74
Q

During the communication between taste cells and afferent nerves, what do type 2 and 3 cells express?

A
  • type 2: ATP via CalHM1 (non-vesicle)
  • type 3: ATP and 5HT (via vesicles)
75
Q

During the communication between taste cells and afferent nerves, what type of nerves are involved?

A
  • somatosensory (5)
  • gustatory (7, 9, 10)
76
Q

During the communication between taste cells and afferent nerves, what occurs in the synapse?

A
  • NTPDase 2 breaks down ATP signals
  • ATP, GABA, and 5HT cause inter-TRC communication
77
Q

During the communication between taste cells and afferent nerves, how do type 2 cells indirectly activate type 3 cells?

A

by releasing ATP

78
Q

During the communication between taste cells and afferent nerves, activated type 3 cells release what to inhibit type 2 cells?

A

GABA and 5HT

79
Q

What are each taste cells innervated by?

A

primary gustatory fibers

80
Q

What are specialist afferent fibers?

A
  • labeled-line coding
  • type 2 cells
81
Q

What are generalist afferent fibers?

A
  • combinatorial coding
  • type 3 cells
82
Q

How do gustatory nerves travel to the cortex?

A
  1. solitary tract to nucleus of solitary tract in the medulla
  2. NST cells send fibers via ventral post. medial thalamus and parabrachial nucleus
  3. info for taste is separated from other senses in gustatory nucleus
83
Q

What are the 3 types of info extracted from tastants?

A

quality, intensity, and hedonic

84
Q

In the CNS, what neuronal responses overlap?

A

sweet, salty and sour (NOT bitter and sweet)

85
Q

Tastant stimuli causes what? What’s the result?

A

motor driven behaviors that result in ingestive/protective responses

86
Q

What nerves innervate the oral cavity?

A

trigeminal sensory nerves

87
Q

What is the main somatosensory innervation of the head?

A

trigeminal (5th cranial nerve)

88
Q

What are the subtyoes in chemesthesis?

A

mechanosensors and nociceptors

89
Q

Nociceptors express what, which are temp. dependent?

A
  • TRPV1: chili, heat, acid
  • TRPA1: wasabi
  • TRPM8: menthol, cold
90
Q

All of following are true regarding olfactory receptors EXCEPT:
A. Olfactory receptors consist of 7 trans-membrane domains
B. TAAR’s are highly selective for specific pheromones
C. A single olfactory receptor nerve can only respond to a single odorant
D. The vomeronasal organ contains specialist receptors in non-ape mammals

A

C

91
Q

Olfactory adaptation exerts its influence in almost all aspects of the functioning of the sense of smell. Which of the following mediates short-term olfactory adaptation?
A. Increased Ca2+ binding to Ca2+ binding protein (cbp)
B. Calmodulin protein kinase II (CaMKII) acting on adenylate cyclase
C. Ca2+-mediated nitric oxide production
D. Increased cGMP production causes persistent Ca2+ influx via CNGA

A

B

92
Q

Taste receptors can be found in small structures known as papillae throughout the tongue and innervated according to their specific location. Which of the following is correctly paired?
A. CN VII; Petrosal ganglion; Foliate papillae
B. CN IX; Petrosal ganglion; Filiform papillae
C. CN VII; Geniculate ganglion; Fungiform papillae
D. CN IX; Geniculate ganglion; Circumvallate papillae

A

C

93
Q

Which of the following mammalian taste cells and receptors are responsible for sensing sweet tastants (i.e. artificial sweeteners)?
A. Type II cells w/ T1R2 + T1R3
B. Type III cells w/ PKD2L1
C. Type II cells w/ T1R1 + T1R3
D. Type I cells w/ ENaC

A

A

94
Q

Projections of the various gustatory nerves (i.e. CN VII, IX, & X) travel to the cortex via which of the following tracts?
A. GN -> NST -> VPM
B. VPM -> NST -> GN
C. NST -> GN -> VPM
D. NST -> VPM -> GN

A

D

Neuroscience Exam 2: Nastassia (9 decks)

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