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Lecture 2 - smell And Taste Flashcards

1
Q

What are the traditional senses?

A 
Smell (olfaction)
Taste (gustatory, gustaoception)
Hearing (audioception)
Sight (vision, opthalmoception)
Touch (tactioception)
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2
Q

Temperature

A

Thermoception

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3
Q

Kinesthetic sense

A

Propioception

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4
Q

Pain

A

Nociception

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5
Q

Balance

A

Equilibrioception

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6
Q

Various internal stimuli

A

Chemoreceptors

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7
Q

What is the cranial nerve for smell?

A

Olfactory (I)

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8
Q

What is the cranial nerve for sight?

A

Optic (II)

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9
Q

What is the cranial nerve for hearing?

A

Vestibulocochlear (VIII)

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10
Q

What is the cranial nerve for Taste?

A

Glossopharyngeal (VII, IX, X)

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11
Q

What is the cranial nerve for touch?

A

Trigeminal (V)

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12
Q

Where are the most common kind of receptor properties found?

A

Terminal ramifications of a sensory axon that belongs to a pseudo-unipolar ganglion cell

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13
Q

Where are the receptors found in the sense organs located?

A

Sensory cells that transmit a signal to a ganglion cell

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14
Q

What are the perception of odours closely associated with,

A

Memories
Emotions
Moods

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15
Q

For humans, what important role does sense of smell have?

A

Interpersonal communication

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16
Q

Humans can sense over how many different odours?

A

10,000

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17
Q

What is the detection threshold?

A

As low as parts per million or even billion

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18
Q

For humans what is smell?

A

Largely an aesthetic sense

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19
Q

How sensitive is smell in scent-tracking in many animals?

A

~ 10.000.000

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20
Q

What does smell direct animals to?

A

Food
Potential mates
Away from danger

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21
Q

Where does the olfactory signalling in humans start?

A

Nasal cavity - olfactory epithelium

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22
Q

Where does the olfactory receptor neutrons send their axons to?

A

Olfactory bulb

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23
Q

Where does the second order Neuton transmit to?

A

Higher cortical areas

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24
Q

What is accessory olfactory pathway (AOP) used for?

A

Pheromone defection

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25
Q

What is pheromone ?

A

Species specific

Affect animal behaviour

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26
Q

What is MOP defined as?

A

Main olfactory system (MOS)

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27
Q

What is AOP defined as?

A

Accessory olfactory system (AOS)

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28
Q

What does the large family of olfactory receptors recognise ?

A

Numerous ligands

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29
Q

How many olfactory receptors are there?

A

~1000

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30
Q

What are olfactory receptors?

A

GPCRs belonging to the odorant receptor gene family

Class “A” GPCR (Opsin or B-adrenergic receptors)

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31
Q

Who was OR discovered by?

A

R.Axel

L.Buck

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32
Q

What does a single odour activate?

A

Multiple ORs

Different combination of ORs are needed for odour recognition

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33
Q

How many OR genes in mouse?

A

1300 (5% of genome)

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34
Q

How many ORs in humans?

A

500 ORs (2% of genome. 50-95% sequence homologous)

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35
Q

How many ORs in Zebrafish?

A

100

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36
Q

How many ORS in C.elegans?

A

1500 (7% of the genome)

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37
Q

What does C.Elegans consist of?

A

Nematode

Roundworms

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38
Q

How many neutrons and chemoreceptor genes does C.elegans have?

A

302 neutrons

1500 chemoreceptor genes (7% of the genome)

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39
Q

How many sensory neutrons express most of the receptors?

A

32

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40
Q

In mammals, how many olfactory nephron expresses one OR gene?

A

1

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41
Q

What are olfactory receptor neurons?

A

Bipolar cells within olfactory epithelium

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42
Q

What does ciliated endings contain?

A

Odorant receptors that detect odours

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43
Q

Where does axons project to?

A

Glomeruli in the olfactory bulb

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44
Q

Where does mitral/tufted cells send information to?

A

Higher brain centres

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45
Q

What is the mechanism of odorant receptors?

A
  1. Odorants bind to receptors
  2. Olfactory receptor cells are activated and send electrical signal
  3. The signals are related in glomeruli
  4. The signals are transmitted to higher regions of brain
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46
Q

What does the sensory transduction of odour molecules involve?

A

Cylic AMP second messenger pathway

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47
Q

What does activation of a receptor by odour molecules activate?

A

GTP binding protein

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48
Q

What does GTP-binding protein activate?

A

Adenylate cyclase which produces cyclic AMP

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49
Q

What does cAMP activate?

A

Cationic cyclic nucleotide-gated channel

Chloride channel

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50
Q

What are olfactory cells?

A

First order neurons

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51
Q

What are mitral cells?

A

Second order neurons onto which axons of olfactory cells synapse

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52
Q

What is the neurotransmitter between olfactory cells and mitral cells?

A

Glutamate

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53
Q

Where does the olfactory neurons send axons to?

A

Olfactory bulb

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54
Q

What is olfactory bulb composed of?

A

Layers

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55
Q

What is the peripheral layer?

A

Glomerular later where the axons of the olfactory neurons terminate

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56
Q

What do many axons converge into?

A

Single glomerulus

57
Q

In rats, how many olfactory neurons converge onto ~ 1500 glomeruli?

A

~ 15 million

58
Q

What do neurons with different ORs send axons to?

A

Different glomeruli

59
Q

What does activation of different receptors lead to?

A

Activation of different glomeruli

60
Q

What does combination of activated glomeruli encode?

61
Q

What do olfactory neurons with the same receptor project to?

A

Same glomerulus

62
Q

What do mitral cells synapse onto?

A

Single glomerulus

63
Q

What are periglomerular cells?

A

Inhibitory interneurons that synapse within and and between glomeruli

64
Q

What are granule cells?

A

Inhibitory interneurons that synapse between mitral/tufted cells

65
Q

What do inhibitory cells use?

A

GABA/Dopamine/Glycine

66
Q

Mitral cells

A

Project directly into olfactory cortex (Glutamate)

67
Q

What is the main cortical area receiving olfactory input ?

A

Pyriform cortex

68
Q

Where does the conscious perception of smell happen?

A

Orbitofrontal cortex

69
Q

Where does pyriform cortex project to?

A

Thalamus via orbitofrontal cortex

70
Q

Where does olfactory tubercle (OT) receive input from?

A

Tufted cells - project to hypothalamus

71
Q

Cortico-medial group amygdala (AMYG)

A

Input from accessory olfactory bulb - hypoth

72
Q

Transitional entorhinal cortex (TEC)

A

Information reaches hippocampus

73
Q

Anterior olfactory nucleus (AON)

A

Cells just posterior to olfactory bulb

74
Q

What does NHLDB stand for?

A

Nucleus of horizontal limb of diagonal band

75
Q

What does MD stand for?

A

Mediodorsal

76
Q

What does VNO stand for?

A

Vomeronasal Organ

77
Q

Where is the primary olfactory cortex located?

78
Q

Where does POC project to?

A

Medial thalamus - orbitofrontal cortex

79
Q

Where does olfactory tubercle project to?

A

Hypothalamus

80
Q

What does pheromone provide information about?

A

Individuals social, sexual or reproductive status

81
Q

What does female snake produce?

A

Substance which can induce courting behaviour in male snakes

82
Q

What does slave maker and emit a blend of?

A

Chemicals that signal alarm

83
Q

What can male dogs sniff?

A

Female in heat

84
Q

Where are pheromones detected in?

A

Accessory olfactory pathway (AOP)

85
Q

Where are pheromone detector barons located in?

A

Vomeronasal Organ (VNO) - anterior nasal septum

86
Q

Where can detection can happen?

A

Openings connecting VNO to either oral or nasal cavities

87
Q

Where does the axons from sensory neurons in VNO travel to?

A

Accessory olfactory bulb (AOB)

88
Q

Does AOP and MOP overlap?

A

No - functional segregation

89
Q

What is the sensory epithelium in VNO divides into?

A

Apical and Basal layer

90
Q

What does neurons in apical layer express?

A

V1R receptors

91
Q

What do neurons in basal layer express?

A

V2R receptors

92
Q

Where does the apical layer project to?

A

Anterior AOB

93
Q

Where does the basal neurons project to?

A

Posterior AOB

94
Q

What does mitral cells interconnect?

A

Different glomeruli

95
Q

What does binding of pheromones to V-R receptors in microvilli activate?

A

PLC through the G protein

96
Q

What does PLC produce?

A

Second messengers DAG and IP3

97
Q

What does the gating of TRPC3 channel by DAG allowable

A

Depolarising influx of Na+ and Ca2+

98
Q

What can intercellular calcium gate?

A

A ca2+ Activated Cl- current

99
Q

How many functional VR1 genes in mice?

100
Q

How many functional VR1 genes in rats?

101
Q

How many functional VR1 genes in humans?

102
Q

How many VR1 genes in humans are pseudo genes?

103
Q

How many VR2 genes in mice and rats?

104
Q

Where do you find a lack of VR2 genes in?

A

Dogs
Cows
Primates

105
Q

What is a TRPC2 gene?

A

Non-functional pseudogene in humans

106
Q

What are other factors that contribute to taste?

A 
Thermoreceptors 
Mechanoreceptors - texture 
Nociceptors 
Sight 
Olfaction
107
Q

What is the gustatory system?

A

Detect soluble chemicals at a short range

108
Q

What is the primary purpose of gustatory system?

A

Identify sources of nutrient rich food and to avoid toxins

109
Q

What is the amino acid and sugars detect threshold?

110
Q

What is bitter detection threshold?

111
Q

What are the taste modalities in mammals?

A 
Sweet 
Bitter 
Sour 
Salty
Umami
112
Q

Where does Mammal taste recognition start?

A

Tongue where taste buds are located

113
Q

What does taste buds contain?

A

Taste deception cells (~100) - epithelial on nature

depolarise and release neurotransmitter

114
Q

Apocalypse, what are receptor cells covered by?

A

Microvilli

Which contain receptors for recognition of taste

115
Q

Basally, what does the cell synapse with?

A

Gustatory nerve

116
Q

What is the neurotransmitter binding to purinoreceptors?

117
Q

What are the other location for taste receptors?

A

Epiglottis

Soft palette

118
Q

What occurs in the gustatory cortex?

A

Gustatory sensory integration occurs

119
Q

What does the gustatory cortex consist of?

A

Insular cortex
Posterior limb
Internal capsule
Frontal operculum

120
Q

What are the main nuclei in rodents of taste perception?

A

NST - nucleus of solitary tract

PBN - parabrachial nuclei

121
Q

What is the main nuclei involved in humans for taste perception?

A

NST - nucleus of solitary tract

VPMpc - ventral posteriomedial nucleus

122
Q

Where are various taste bud population found In?

A

Fungiform papillae - anterior tongue

Palate and foliate papillae - posterior tongue

123
Q

What are taste buds innervated by?

A

Branches of VIIth, IXth, Xth cranial nerves

124
Q

What does the buds on palate and epiglottis contact?

A

Xth cranial nerve

125
Q

What is the gustatory pathway in humans?

A

The afferent fibres collect in rostral solitary nucleus of Medulla oblongata
The axon ascend ipsilaterally into central tegmental tract of brain stem terminating in parvocellular division of central posteriomedial nucleus in thalamus
Go into gustatory neocortex
Enter limbic system

126
Q

What is the gustatory pathway in rodents?

A

The axon of the peripheral gustatory fibre in facial, glossopharnygeal and vagal cranial nerve lead into nucleus of solitary tract in Medulla oblongata
Leads to parabrachial nucleus followed by ventral posteriomedial nucleus in thalamus
From thalamus the neurons project into gustatory neocortex
Project into hypothalamus and amygadala

127
Q

How many taste cells does the taste bf contain?

A

50-100 taste cells

128
Q

What does epithelial receptor cells make synaptic contact with?

A

Dendrites of cranial nerve VII, IX or X

Cell bodies lie within cranial nerve Ganglia

129
Q

How is the characteristic spindle shape of taste receptor cells revealed?

A

Subset of taste cells labelled with antibody against alpha-gustducin

130
Q

Mice lacking T1R1

A

Do not detect amino acids

131
Q

Mice lacking T1R2

A

Do not detect sugars

132
Q

How are tests confirmed?

A

Behavioural testing of mice preference to different foods

133
Q

What can humans detect?

134
Q

What can humans detect?

A

Sweetness in aspartame

135
Q

What does the activation of a receptor activate?

A

Heterotrimeric G protein
Activates phospholipase C-B2 (PLC B2)
Produce secondary messenger IP3 and DAG
Activation of PLC-B2 lead to opening of TRPM5 ion channel and cell depolarisation.

136
Q

What are sour taste associated with?

A

PKD1L3/PKD2I1 channels

Intensity of sour taste various with proton concentration

137
Q

What are salty taste mediated by?

A

ENaC sodium channels
Expressed apically in salt sensing cells
Na+ diffuses passively to cause depolarisation
Removed at the vascular membrane NaK-ATPase

138
Q

What are 75% of humans able to detect?

A

Phenylthiocarbamide

Found in Brussels sprouts

139
Q

What allows for full taste perception?

A

Cingulate gyrus

Secondary neocortical taste area in caudolatetal orbitofrontal cortex

System Neuroscience (17 decks)

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