1
Q
the action of tasting
A
gustation
2
Q
smelling
A
olfaction
3
Q
organisms detect chemicals using
A
chemoreceptors
4
Q
What are the chemical senses?
A
- taste
- smell
5
Q
What 5 behaviours do chemical stimuli play an important role in?
A
- feeding and food preference
- territorial recognition
- avoiding predators
- mating
- social activities
6
Q
What are 4 internal chemical monitors?
A
- blood
- glucose
- CO2
- pH
7
Q
What are 4 external chemical monitors
A
- taste
- smell
- pheromones
- chemesthesis
8
Q
What is the new definition of taste?
A
metabolic sense
9
Q
the anatomically defined chemical stimulation of specific receptors leading to the perception of the primary modalities
A
Old definition of taste
10
Q
With regards to the transduction of chemical signals, external chemicals can do what two things?
A
- interact with receptors on the plasma membrane
- metabolic receptors
- ionotropic receptors
- ion channels - cross the cell membrane to directly interact with secondary messenger systems or intracellular receptors
11
Q
What are the 3 appetitive tastes?
A
- sweet
- umami
- salty
12
Q
This taste includes sugars/carbohydrates which provide metabolic energy
A
sweet
13
Q
This taste includes a meaty/savory taste
A
umami
14
Q
This taste senses ions critical for cellular function
A
salty
15
Q
What are the 3 aversive tastes?
A
- bitter
- sour
- too salty
16
Q
This taste senses broad-spectrum of potentially poisonous compounds
A
bitter
17
Q
This taste may help detect rotting food
A
sour
18
Q
This taste causes excessive dehydration
A
too salty
19
Q
What are examples of salty taste qualities?
A
- NaCl
- LiCl
(minerals)
20
Q
What are examples of Umami?
A
- glutamate
- aspartate
- nucleotides
(proteins, calories)
21
Q
What is an example of sour taste?
A
acids
(ripeness)
22
Q
What are examples of sweet taste?
A
- sugars
- high intensity sweeteners
(calories for plant eating animals)
23
Q
What are examples of bitter tastes?
A
- alkaloids
- peptides
- toxins
(poison avoidance, nutrient recognition?)
24
Q
What are 6 non-conventional taste qualities?
A
- fat taste
- tactile sensation
- have own taste receptors - carbonation
- metallic taste
- kokumi
- flavour enhancement mediated by calcium channels - starch
- water
25
What are 4 additional taste modalities?
1. calcium
2. water
3. CO2
4. pyrophosphates
26
What three things make up flavour?
1. taste
2. olfaction
3. chemical irritation
27
What are the 3 functions of flavour?
1. evaluate food and drink
2. motivate ingestion or rejection
3. act as a trigger for "cephalic phase" of digestion and metabolism
- initiates exocrine and endocrine responses that anticipate arrival of food in gut
28
Is taste involved in dietary preference?
it could be, but there's little data from humans
29
Can taste preferences be learned?
Yes.
conditioned responses and assocative learning
30
Describe the development of taste perception for salt
- increases with age
- wanes after age 2
- may relate to organ development
31
What taste do newborns prefer?
sweet because it corresponds with milk
32
What taste do infants prefer?
- what's good for them
- infant with imbalance in adrenal hormones that regulate salt had craving for salty foods
33
Why have breast-fed babies been shown to out-perform bottle fed babies?
1. nutrition in breast milk
2. difference in social relationship
- unlikely, babies fed breast milk through tubes (different interaction) still outperformed babies fed by formula
3. maternal education
34
True or false: Cats cannot taste sweets
True! they have lost sweet function. As well as other obligate carnivores
35
Why can't cats taste sweets?
- gene for Cat T1R2 is defective
- has stop codons so cannot signal sweet taste
- pseudogene
- can be thought of as a molecular fossil
36
What are the implications of the defective T1R2 genes in cats?
- no response to cabohydrates
- great response to amino acids
37
What receptor is involved with sweet and umami in giant pandas?
- no response to amino acids (no umami receptor)
- great response to cabohydrates
38
What receptor is involved with sweet and umami in obligate carnivores?
T1R3 = sweet
T1R3 and T1R1 = amino acid, umami
39
gustation
taste system
40
Describe the taste system
- taste buds are receptor cells
- input to medulla, and from there to thalamus and limbic system
41
Describe taste development during the 1st, 2nd and 3rd trimesters
42
When is the ability to taste fully developed?
at birth, there is an increase in the number of taste buds
43
The tongue is a mass of skeletal muscle that is covered by
mucous membrane
44
Describe the oral, or anterior 2/3 part of the tongue
faces upwards towards the hard palate
45
Describe the pharyngeal, or posterior 1/3 of the tongue
faces backwards towards the oropharynx
46
What parts of the tongue are keratinised and non-keratinised?
oral = keratinised
pharyngeal = non-keratinised
47
What type of epithelium is the tongue?
stratified squamous epithelium
48
What are the two parts of the tongue (anterior 2/3 and posterior 1/3) separated by?
sulcus terminalis
49
All intrinsic and extrinsic muscles of the tongue are supplied by which nerve?
hypoglossal
50
Which muscle of the tongue is the exception and is supplied by a different nerve? What nerve?
palatoglossus is supplied by pharyngeal plexus (vagus and glossopharyngeal nerve)
51
The general sensation of the anterior 2/3 of the tongue comes from which nerve?
lingual nerve which is a branch of the mandibular nerve and has cell bodies in trigeminal ganglion
52
Taste in the anterior 2/3 of the tongue comes from which nerve?
chorda tympani (with cell bodies in the geniculate ganglion of facial nerve)
53
What is the nerve supply for general sensation and taste in the posterior 1/3 of the tongue?
glossopharyngeal nerve with cell bodies in glossopharyngeal ganglia in jugular foramen
54
What is the nerve supply for the posterior most part of the tongue?
vagus (CN X) nerve through the internal laryngeal branch (with cell bodies in the inferior vagal ganglion)
55
Chorda tympani is a branch of which nerve?
facial nerve VII
56
Where are the cell bodies of taste related fibers of the chorda tympani located?
geniculate ganglion
57
This is a mixed nerve which contains both sensory afferent and motor efferent fibers
glossopharyngeal nerve IX
58
Where does the glosspharyngeal nerve IX carry information?
- from posterior 1/3 of tongue and up the pharynx
- other head/throat areas
59
Where are the taste fiber cell bodies of the glosspharyngeal nerve IX located?
inferior glosspharyngeal ganglion
60
The trigeminal nerve (CN V) is responsible for many non-taste somatosensory sensations in the mouth such as
1. tactile (texture, viscosity)
2. heat/cool
3. nociception (pain)
61
The trigeminal nerve (CN V) is also critical for two oral motor functions, what are they?
1. biting
2. chewing
62
Why is it important that the trigeminal nerve combines non-taste senses with taste perception?
hot spiciness of peppers is the result of pain receptor activation by capcaisin
63
These papillae are scattered across the anterior portion of the tongue
fungiform papillae
64
fungiform papillae are innervated by
chorda tympani branch of facial nerve VII
65
These papillae are located in folds on the lateral portion of the posterior tongue
foliate papillae
66
Foliate papillae are innervated by
1. chorda tympani
2. glossopharyngeal
67
These papillae are located in semi-circular crevices at the center of the posterior tongue
circumvallate papillae
68
The circumvallate papillae are innervated by which nerve?
glossopharyngeal
69
This type of papillae is similar to fungiform in morphology and is sensitive to all taste qualities, sweet in particular
papillae of soft palate
70
The papillae of the soft palate is innervated by
greater petrosal branch of the facial nerve (VII)
71
The taste bud is a multi-cellular organelle comprised of 50-75 cells, however only ___ function as receptors.
7-10
72
True or false: We know lots about the neurotransmitters produced by taste bud cells
False, we know little
73
Describe cell turnover in the taste bud
continual migration into and out of the pore region
74
What are the 3 taste bud containing papillae?
1. fungiform
2. foliate
3. circumvallate
75
What is the non-taste papillae?
filiform papillae
76
In addition to the tongue, where are 4 other places taste buds are found?
1. soft palate
2. cheeks
3. upper esophagus
4. epiglottis
77
This type of taste cell has glial-like support cells and may express salt receptors
type 1
78
This type of taste cell express receptors for sweet, bitter, and umami. Cells tend to be narrowly tuned to a single taste quality.
Type 2, aka receptor cells
79
This type of taste cell expresses receptors for sour and salty taste and can respond to 3 taste qualities on average.
Type 3, aka presynaptic cells
80
This type of taste cell is a precursor cell, or taste stem cell.
Type IV
81
How are receptor cells in a taste bud organized?
different tastes seem to be segregated
82
inability to detect gustatory stimulants
ageusia
83
a diminished ability to detect gustatory stimulants
hypogeusia
84
increased sensitivity to gustatory stimulants
hypergeusia
85
distorted perception of taste stimulants (i.e., unpleasant taste)
dysgeusia (parageusia)
86
inability to identify or classify a stimulant although properly perceived
taste agnosia
87
inability to detect olfactory stimulants
anosmia
88
a diminished ability to detect olfactory stimulants
hyposmia
89
increased sensitivity to olfactory stimulants
hyperosmia
90
distorted perception of olfactory stimulants (i.e., unpleasant order sensation)
dysosmia (cacosmia)
91
inability to identify or classify a stimulant although properly perceieved
olfactory agnosia
92
What are the two classes of taste receptors?
1. G-protein coupled
2. ion channels
93
What are the three types of T1Rs (G-protein coupled receptors)?
T1R1
T1R2
T1R3
94
This GPCR is responsible for sweet and umami taste
T1R family
95
This GPCR has a very long n-terminal domain, is structurally related to glutamate and Ca receptors, and forms heterodimers
T1R
96
solves the problem of multiple stimuli of varying structure by having multiple receptor sites on one heterodimer
T1R
97
This GPCR is responsible for bitter taste
T2R
98
This GPCR is structurally related to olfactory receptors and has a short n-terminus
T2R
99
Solves the problem of having to detect large number of bitter stimuli by having many receptors (6-50, depending on the species) of broad specificity
T2R
100
These channel proteins are related as belonging to the degenerin family, salty and sour
stimulus-gated ion channels
101
What is responsible for salty taste?
Na+ channels, such as ENaC
102
Differentiate between intracellular receptors and cell surface receptors
103
Process in which cells sense the extracellular stimuli through membranous or intracellular receptors, transduce the signals via intracellular molecules. This process also regulates the biological function of cells.
Cell signalling
104
What are the 5 features of signal transduction?
1. specificity
2. affinity
3. amplification
4. desensitization
5. integration
105
signal molecules fit binding site on its complementary receptor, other signals do not
specificity
106
high affinity of receptors of signal molecules
affinity
107
signal receptor activate many molecules of second enzyme, which activates many molecules of the third enzyme and so on
amplification
108
feedback circuit that shuts off the receptor or removes it from the cell
desensitization
109
two signals with opposite action on second messenger, the regulatory outcome results form integrated output from both receptors
integration
110
What are 12 signals to which cells respond?
1. antigen
2. cell surface glycoproteins/oligosaccharides
3. extracellular matrix
4. growth factors
5. hormones
6. neurotransmitters
7. light
8. mechanical touch
9. nutrients
10. odorants
11. pheromones
12. tastants
111
This type of messenger transmits signals from the receptor to the enzyme and activate it to produce a secondary messenger. (Ex. Gα,Gβγ)
Primary messenger
112
This type of messenger transmits signals in form of either direct cellular response (cAMP, cGMP) or activates further enzymes to produce a response (IP3, DAG)
secondary messenger
113
This type of messenger releases after action of second messenger on an organelle and act directly or in conjuction to give cellular responses (ex. Ca2+)
tertiary messenger
114
What is the structure of a g-protein coupled receptor?
1. 7TM a helices (seven transmembrane) coupled to an effector system through GTP/GDP binding protein called G-proteins
2. intracellular domain = couples to g-protein
3. extracellular domain = binds to the ligand (drug/neurotransmitter)
115
Where does G-protein get its name from?
interaction with guanine nucleotides (GTP/GDP)
116
When the g-protein is bound to GTP, is it "on" or "off"?
on
117
When the g-protein is bound to GDP, is it "on" or is it "off"?
off
118
How many subunits does G-protein have? What are they?
α, β and γ
119
What subunit do guanine nucleotides bind to?
α
120
A family of membrane proteins anchored to the membrane which are metabotropic receptors that act through a secondary messenger
G-protein
121
What are the two types of G proteins?
1. large (heterotrimetric)
2. small
122
This type of g-protein is activated by GPCRs and is made up of α (alpha), β (beta) and γ (gamma) subunits.
Large G proteins (heterotrimetric)
123
This type of g-protein belongs to the Ras superfamily, is homologous to the α subunit, and also binds GTP and GDP for signal transduction
small G proteins
124
Name the G-protein subunits and their second messengers
125
Golf-odorant receptor
adenylyl cyclase
126
What happens when Gt-cGMP phosphodiesterase increases?
cGMP decreases
127
What does the Ga12/13-Rho family GTPase do?
1. control cell cytoskeleton remodelling
2. regulating cell migration
128
What is the mechanism of GPCR?
129
Describe hormones and signal transduction for GPCRs and G-proteins
1. G-Proteins Bind Guanine Nucleotides (GDP and GTP)
2. Heterotrimeric -α,β,γ Subunits
3. Associate with GPCRs
4. Altered by GPCR’s Binding of Hormone
130
Describe hormones and signal transduction for B-andrenergic receptors.
131
Describe PKA activation
132
Describe the phospholipase-c signalling system
133
What are the 9 GPCR classes?
134
What are the 4 targets of g-proteins?
1. adenylyl cyclase
2. IP3/DAG phospholipase c cystem
3. ion channels eso. potassium and calcium
4. rho a/Rho kinase system
135
What 4 things is the adenylyl cyclase/cAMP system involved in?
1. energy metabolism
2. cell division and cell differentiation
3. ion transport, ion channels
4. contractile proteins in smooth muscle
136
What is the common mechanism of the adenylyl cyclase/cAMP system?
activation of protein kinases
137
True or false: cAMP is a nucleotide
True
138
How is cAMP synthesized?
within the cell from ATP by adenylyl cyclase
139
Is cAMP produced continuously?
yes
140
How is cAMP inactivated?
hydrolysis to 5-AMP by phosphodiesterases
141
cAMP response element-binding protein leads to
1. tyrosine hydroxylase
2. iNOS
3. AchR
4. angiotensinogen
5. insulin
6. glucocorticoid receptor
7. CFTR
142
What is the best understood target of cyclic AMP?
protein kinase
143
What does the EPAC pathway provide an additional effector for?
cAMP signalling and drug actin that can act independently or cooperatively with PKA
144
What are the regulators of cell function?
monomeric GTPases
145
The activation of diverse signaling pathways, regulates what 5 things?
1. phagocytosis
2. progression through cell cycle
3. cell adhesion
4. gene expression
5. apoptosis
146
hydrolyze the cyclic 3',5'-phosphodiester bond in cAMP and cGMP
phosphodiesterases
147
How many different proteins and subfamilies do phosphodiesters have?
> 50 different PDE proteins
11 subfamilies
148
Phosphodiesterases are drug targets for what 4 things?
1. astha
2. cardiovascular diseases, (i.e., heart failure)
3. atheroscleortic coronary and peripheral arterial disease
4. neruological disorders
149
What is phosphodiesterase inhibited by?
caffeine
150
What is the substrate for membrane-bound enzyme phospholipase CB (PLCB)?
PIP2
151
What does PIP2 split PCLB into?
1. DAG
2. inositol (1,4,5, triphosphate) (IP3)
**both are secondary messengers
152
What happens after PIP2 is cleaved?
status quo restored
153
What blocks the recycling pathway?
lithium
154
a ligand-gated calcium channel present on the membrane of the endoplasmic reticulum
IP3 receptor
155
___, unlike the inositol phosphates, is highly lipophilic and remains within the membrane
DAG
156
How many different mammalian PKC subtypes are there?
10
157
play a central role in signal transduction, and control many different aspects of cell function
kinases
158
DAG
diacylglycerol
159
a ligand gated Ca2+ channel found in high concentrations in the membrane of the ER
IP3 receptor
160
What concentration enhances Ca2+ release?
10^-9
161
What concentration inhibit Ca2+ release?
10^-9
162
What enhances Ca2+ release?
phosphorylation of IP3 receptor by PKA
163
What inhibits Ca2+ release?
phosphorylation of an accessory protein, IRAG, by PKG
164
What happens in smooth muscle as a result of PKG?
relaxation of vessel tone by cyclic GMP
165
In skeletal and cardiac muscle, what is released through intracellular stores?
ca2+
166
Ca2+ in skeletal and cardiac muscle is mediated by
the ryanodine receptor (RyR)
167
What is an example of a drug that activates RyR
caffeine
168
What is an example of a drug that inhibits RyR
Dantrolene
169
In cardiac muscle, what enhances K+ permeability?
mAChRs
170
reduces excitability by opening potassium channels
opiate analgesics
171
Actions are produced by direct interaction between the βγ subunit of G0 and the channel, without the involvement of second messengers
ion channels
172
How is the Rho/Rho kinase system activated?
GPCRs (and non-GPCRs) which couple G12/13 type proteins
173
Rho-GDP
resting, inactive form
174
Rho-GTP
active form
175
What happens when Rho is activated?
1. Rho kinase activated
2. smooth muscle contraction and proliferation
2. angiogenesis
3. synaptic modeling
176
What system is important in the pathogenesis of pulmonary hypertension
Rho/Rho kinase system
177
Compare and contrast the two types of desensitization
178
How many GPCRs are orphan (unknown)?
200
179
homozygous loss of function mutations in the type 5 chemokine receptor provides resistance to
HIV infection
180
True or false: Loss of function and gain of function mutations in GPCRs can cause disease
true
181
Of the drugs approved for marketing by the FDA, how many target GPCRs?
40%
182
Of the 800-1,000 different GPCRs, the drugs that are marketed target how many?
GPCRs
