Module 3: Gustation Flashcards
which cranial nerve supplies the taste buds (epiglottis)
CNX
which cranial nerve supplies the taste buds (posterior 1/3 of the tongue)
CN IX
which cranial nerve supplies the taste buds (anterior 2/3 of the tongue)
CN VII
where do the taste buds transmit information to
medulla nucleus of the solitary tract
what brain structures does the medulla nucleus of the solitary tract have back-and-forth connections with
hypothalamus and amygdala
what are the hypothalamus and amygdala involved in
pleasure, aversion, food seeking behavior, satiety
where does the medulla nucleus of the solitary tract project to
VTM of thalamus
where does the VTM of thalamus project to
insular and frontal taste cortices
where does the insular and frontal taste cortices project to
amygdala
what are the three subdivisions of papillae
fungiform (tip), foliate (sides), circumvallate (back, 8 - 10 count)
what are the tastes
sweet, salty, sour, bitter, umami, fat
what is CD36
a taste receptor localized to circumvallate and foliate papillae that binds to fatty acids
how many taste buds does each papillae contain
1-100
how many taste receptors does each taste bud contain
50-150 taste receptor
- also contain basal cells (stem cells that create receptors)
type I cell function
support cell (glial-like function)
type II cell function
detects sweet, umami, and bitter tastes
type III cell function
detects sour, salt receptors
what neurotransmitters do type II cells release
ATP
what neurotransmitters do type III cells release
serotonin
microvilli function
project to the taste pore where they are exposed to tastands
where do taste receptors synapse
gustatory afferent axons
which part of the tongue mostly senses sour
sides
which part of the tongue mostly senses bitter
back
which part of the tongue mostly senses salty and sweet
front and sides
how does the insular cortex relate to taste
taste receptors make connections to insular cortex, and it has different areas for each type of taste
which tastes do humans have an innate preference for
sweet, umami, and salt
what is our threshold for detecting sour taste?
0.0009 M
what is our threshold for detecting salty taste?
0.01 M
what is our threshold for detecting sweet taste?
0.01 M
what is our threshold for detecting bitter taste?
0.000008 M
what does too much salt cause
high blood pressure, higher chance for cardiovascular diseases, heart attack, and stroke
advantage of artificial sweeteners
less risk of obesity
disadvantage of artificial sweeteners
weight gain, insulin resistance, T2 diabetes, cardiovascular disease, and mortality
what is the overview of the salty pathway
Na+ ions enter through amiloride-sensitive Na+ channesl
what is the overview of the sour pathway
H+ enters through H+ - sensitive TRP-channel (polycystic kidney disease (PKD) variant))
what is the overview of the sweet pathway
heterodimer consisting of G-protein-coupled receptors T1R2 & T1R3
what is the overview of the umami pathway
T1R1 & T1R3 GPCR & TRPM5 channel (Ca2+ goes through)
what is the overview of the bitter pathway
T2R (gustuducin) –> alpha –>IP3 –> TRPM5 channel w/ Ca2+
how many taste receptors are able to detect bitter substances
30 taste receptors
what does higher concentration of intracellular Ca2+ cause in a type II taste cell
increases activity of TRPM5 channels
what does increased activity of TRPM5 channels do
increases influx of Na+, depolarizing the cell
what results from Calhm1 and P2X receptor knockout in mice
loss of perception of sweet, umami, and bitter compounds
what is STIM1
endoplasmic reticulum Ca2+ sensor
what is Plc
phospholipase C
what does Ca2+ do under resting conditions in Type II taste cells
is stored in ER; STIM1 bond with Ca & uniformly distributed within ER membrane
what happens when Ca store is depleted
Ca2+ unbinds STIM1 and triggers its oligomerization and migration ==> ER membrane junctions; activation of store-operated Ca channels (SOC)
what are the receptor proteins for sweet
T1R2, T1R3
what are the receptor proteins for umami
T1R1, T1R3
what are the receptor proteins for bitter
T2Rs
what does KO of T1R2 do
loss of ability to taste sweet
what does KO of T1R1 do
loss of umami taste
what does KO of T1R3 do
loss of sweet and umami taste
which cells is T2Rs expressed in
cells that don’t express sweet/umami receptors
what is TRPM5 involved in
taste of sweet and umami
what does KO of TRPM5 result in
mice don’t avoid water with quinine
what kind of signal processing does the brain have for taste
labeled line coding
can one receptor be activated by more than one tastant?
yes in real life, but we will assume that only one receptor can be activated by 1 tastant
where are taste signals sent
gustatory axons
where do gustatory axons project
brainstem
where does brainstem project
thalamus
where does thalamus project
cerebral cortex
what is flavor
overall sensation (taste, touch, pain, and smell)
