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)
2
Q
Temperature
A
Thermoception
3
Q
Kinesthetic sense
A
Propioception
4
Q
Pain
A
Nociception
5
Q
Balance
A
Equilibrioception
6
Q
Various internal stimuli
A
Chemoreceptors
7
Q
What is the cranial nerve for smell?
A
Olfactory (I)
8
Q
What is the cranial nerve for sight?
A
Optic (II)
9
Q
What is the cranial nerve for hearing?
A
Vestibulocochlear (VIII)
10
Q
What is the cranial nerve for Taste?
A
Glossopharyngeal (VII, IX, X)
11
Q
What is the cranial nerve for touch?
A
Trigeminal (V)
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
13
Q
Where are the receptors found in the sense organs located?
A
Sensory cells that transmit a signal to a ganglion cell
14
Q
What are the perception of odours closely associated with,
A
Memories
Emotions
Moods
15
Q
For humans, what important role does sense of smell have?
A
Interpersonal communication
16
Q
Humans can sense over how many different odours?
A
10,000
17
Q
What is the detection threshold?
A
As low as parts per million or even billion
18
Q
For humans what is smell?
A
Largely an aesthetic sense
19
Q
How sensitive is smell in scent-tracking in many animals?
A
~ 10.000.000
20
Q
What does smell direct animals to?
A
Food
Potential mates
Away from danger
21
Q
Where does the olfactory signalling in humans start?
A
Nasal cavity - olfactory epithelium
22
Q
Where does the olfactory receptor neutrons send their axons to?
A
Olfactory bulb
23
Q
Where does the second order Neuton transmit to?
A
Higher cortical areas
24
Q
What is accessory olfactory pathway (AOP) used for?
A
Pheromone defection
25
What is pheromone ?
Species specific
| Affect animal behaviour
26
What is MOP defined as?
Main olfactory system (MOS)
27
What is AOP defined as?
Accessory olfactory system (AOS)
28
What does the large family of olfactory receptors recognise ?
Numerous ligands
29
How many olfactory receptors are there?
~1000
30
What are olfactory receptors?
GPCRs belonging to the odorant receptor gene family
| Class “A” GPCR (Opsin or B-adrenergic receptors)
31
Who was OR discovered by?
R.Axel
| L.Buck
32
What does a single odour activate?
Multiple ORs
| Different combination of ORs are needed for odour recognition
33
How many OR genes in mouse?
1300 (5% of genome)
34
How many ORs in humans?
500 ORs (2% of genome. 50-95% sequence homologous)
35
How many ORs in Zebrafish?
100
36
How many ORS in C.elegans?
1500 (7% of the genome)
37
What does C.Elegans consist of?
Nematode
| Roundworms
38
How many neutrons and chemoreceptor genes does C.elegans have?
302 neutrons
| 1500 chemoreceptor genes (7% of the genome)
39
How many sensory neutrons express most of the receptors?
32
40
In mammals, how many olfactory nephron expresses one OR gene?
1
41
What are olfactory receptor neurons?
Bipolar cells within olfactory epithelium
42
What does ciliated endings contain?
Odorant receptors that detect odours
43
Where does axons project to?
Glomeruli in the olfactory bulb
44
Where does mitral/tufted cells send information to?
Higher brain centres
45
What is the mechanism of odorant receptors?
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
46
What does the sensory transduction of odour molecules involve?
Cylic AMP second messenger pathway
47
What does activation of a receptor by odour molecules activate?
GTP binding protein
48
What does GTP-binding protein activate?
Adenylate cyclase which produces cyclic AMP
49
What does cAMP activate?
Cationic cyclic nucleotide-gated channel
| Chloride channel
50
What are olfactory cells?
First order neurons
51
What are mitral cells?
Second order neurons onto which axons of olfactory cells synapse
52
What is the neurotransmitter between olfactory cells and mitral cells?
Glutamate
53
Where does the olfactory neurons send axons to?
Olfactory bulb
54
What is olfactory bulb composed of?
Layers
55
What is the peripheral layer?
Glomerular later where the axons of the olfactory neurons terminate
56
What do many axons converge into?
Single glomerulus
57
In rats, how many olfactory neurons converge onto ~ 1500 glomeruli?
~ 15 million
58
What do neurons with different ORs send axons to?
Different glomeruli
59
What does activation of different receptors lead to?
Activation of different glomeruli
60
What does combination of activated glomeruli encode?
Smell
61
What do olfactory neurons with the same receptor project to?
Same glomerulus
62
What do mitral cells synapse onto?
Single glomerulus
63
What are periglomerular cells?
Inhibitory interneurons that synapse within and and between glomeruli
64
What are granule cells?
Inhibitory interneurons that synapse between mitral/tufted cells
65
What do inhibitory cells use?
GABA/Dopamine/Glycine
66
Mitral cells
Project directly into olfactory cortex (Glutamate)
67
What is the main cortical area receiving olfactory input ?
Pyriform cortex
68
Where does the conscious perception of smell happen?
Orbitofrontal cortex
69
Where does pyriform cortex project to?
Thalamus via orbitofrontal cortex
70
Where does olfactory tubercle (OT) receive input from?
Tufted cells - project to hypothalamus
71
Cortico-medial group amygdala (AMYG)
Input from accessory olfactory bulb - hypoth
72
Transitional entorhinal cortex (TEC)
Information reaches hippocampus
73
Anterior olfactory nucleus (AON)
Cells just posterior to olfactory bulb
74
What does NHLDB stand for?
Nucleus of horizontal limb of diagonal band
75
What does MD stand for?
Mediodorsal
76
What does VNO stand for?
Vomeronasal Organ
77
Where is the primary olfactory cortex located?
Uncus
78
Where does POC project to?
Medial thalamus - orbitofrontal cortex
79
Where does olfactory tubercle project to?
Hypothalamus
80
What does pheromone provide information about?
Individuals social, sexual or reproductive status
81
What does female snake produce?
Substance which can induce courting behaviour in male snakes
82
What does slave maker and emit a blend of?
Chemicals that signal alarm
83
What can male dogs sniff?
Female in heat
84
Where are pheromones detected in?
Accessory olfactory pathway (AOP)
85
Where are pheromone detector barons located in?
Vomeronasal Organ (VNO) - anterior nasal septum
86
Where can detection can happen?
Openings connecting VNO to either oral or nasal cavities
87
Where does the axons from sensory neurons in VNO travel to?
Accessory olfactory bulb (AOB)
88
Does AOP and MOP overlap?
No - functional segregation
89
What is the sensory epithelium in VNO divides into?
Apical and Basal layer
90
What does neurons in apical layer express?
V1R receptors
91
What do neurons in basal layer express?
V2R receptors
92
Where does the apical layer project to?
Anterior AOB
93
Where does the basal neurons project to?
Posterior AOB
94
What does mitral cells interconnect?
Different glomeruli
95
What does binding of pheromones to V-R receptors in microvilli activate?
PLC through the G protein
96
What does PLC produce?
Second messengers DAG and IP3
97
What does the gating of TRPC3 channel by DAG allowable
Depolarising influx of Na+ and Ca2+
98
What can intercellular calcium gate?
A ca2+ Activated Cl- current
99
How many functional VR1 genes in mice?
165
100
How many functional VR1 genes in rats?
106
101
How many functional VR1 genes in humans?
2
102
How many VR1 genes in humans are pseudo genes?
115/117
103
How many VR2 genes in mice and rats?
~60
104
Where do you find a lack of VR2 genes in?
Dogs
Cows
Primates
105
What is a TRPC2 gene?
Non-functional pseudogene in humans
106
What are other factors that contribute to taste?
```
Thermoreceptors
Mechanoreceptors - texture
Nociceptors
Sight
Olfaction
```
107
What is the gustatory system?
Detect soluble chemicals at a short range
108
What is the primary purpose of gustatory system?
Identify sources of nutrient rich food and to avoid toxins
109
What is the amino acid and sugars detect threshold?
10-100 mM
110
What is bitter detection threshold?
< 0.02 mM
111
What are the taste modalities in mammals?
```
Sweet
Bitter
Sour
Salty
Umami
```
112
Where does Mammal taste recognition start?
Tongue where taste buds are located
113
What does taste buds contain?
Taste deception cells (~100) - epithelial on nature
| depolarise and release neurotransmitter
114
Apocalypse, what are receptor cells covered by?
Microvilli
| Which contain receptors for recognition of taste
115
Basally, what does the cell synapse with?
Gustatory nerve
116
What is the neurotransmitter binding to purinoreceptors?
ATP
117
What are the other location for taste receptors?
Epiglottis
| Soft palette
118
What occurs in the gustatory cortex?
Gustatory sensory integration occurs
119
What does the gustatory cortex consist of?
Insular cortex
Posterior limb
Internal capsule
Frontal operculum
120
What are the main nuclei in rodents of taste perception?
NST - nucleus of solitary tract
| PBN - parabrachial nuclei
121
What is the main nuclei involved in humans for taste perception?
NST - nucleus of solitary tract
| VPMpc - ventral posteriomedial nucleus
122
Where are various taste bud population found In?
Fungiform papillae - anterior tongue
| Palate and foliate papillae - posterior tongue
123
What are taste buds innervated by?
Branches of VIIth, IXth, Xth cranial nerves
124
What does the buds on palate and epiglottis contact?
Xth cranial nerve
125
What is the gustatory pathway in humans?
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
What is the gustatory pathway in rodents?
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
How many taste cells does the taste bf contain?
50-100 taste cells
128
What does epithelial receptor cells make synaptic contact with?
Dendrites of cranial nerve VII, IX or X
| Cell bodies lie within cranial nerve Ganglia
129
How is the characteristic spindle shape of taste receptor cells revealed?
Subset of taste cells labelled with antibody against alpha-gustducin
130
Mice lacking T1R1
Do not detect amino acids
131
Mice lacking T1R2
Do not detect sugars
132
How are tests confirmed?
Behavioural testing of mice preference to different foods
133
What can humans detect?
Glutamate
134
What can humans detect?
Sweetness in aspartame
135
What does the activation of a receptor activate?
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
What are sour taste associated with?
PKD1L3/PKD2I1 channels
| Intensity of sour taste various with proton concentration
137
What are salty taste mediated by?
ENaC sodium channels
Expressed apically in salt sensing cells
Na+ diffuses passively to cause depolarisation
Removed at the vascular membrane NaK-ATPase
138
What are 75% of humans able to detect?
Phenylthiocarbamide
| Found in Brussels sprouts
139
What allows for full taste perception?
Cingulate gyrus
| Secondary neocortical taste area in caudolatetal orbitofrontal cortex
