Taste Flashcards
taste buds contain ___ taste cells
50-100
the 5 taste modalities are…
fat, umami, salt, bitter, sour and sweet
we have ____ taste buds
~5000
taste cells contain ___ which house ____
microvilli, taste receptors
label this diagram:
a: sensory neuron
b: nerve fiber
c: microvilli containing taste receptors
where are taste buds?
in 3 kinds of papillae (folds) in the tongue
what are the 3 kinds of papillae?
Fungiform, foliate, circumvallate
describe fungiform
- 250; each contain 1-5 taste buds
- Simplest; have microvilli on the surface
describe foliate
20; each contain 100-50 taste buds, small invagination
describe circumvallate
8-10; each contain 250 taste buds
- account for half of the total taste buds.
- Near the back of the tongue.
- Contain deep grooves where saliva can enter and expose tastants to taste buds.
taste cells have a lifespan of _____; they regenerate due to being exposed to the _____
1 week, environment
label this diagram:
a: circumvallate
b: foliate
c: fungiform
taste cells form ____ based on what ___ they reside in
afferents, papillae
What cranial nerves do fungiform, foliate, circumvallate, and epiglottic taste receptors contribute to?
Fungiform: CN VII
Foliate: CN IX and CN VII
Circumvallate: CN IX
Epiglottic: CN X
What ganglion cells constitute the Facial Nerve (CN VII)
geniculate ganglion cells.
what nerves innervate facial nerve CN VII?
It is innervated by the greater petrosal and chorda tympani nerves
where does facial nerve CN VII collect sensory info from?
the anterior ⅔ of the tongue.
What ganglion cells constitute the Glossopharyngeal Nerve (CN IX)?
inferior ganglion cells.
what innervates glossopharyngeal nerve CN IX?
pestrosal ganglion cells
where does glossopharyngeal nerve CN IX collected sensory info from?
from the posterior ⅓ of the tongue.
what ganglion cells constitute the vagus nerve CN X?
inferior/nodose ganglion cells
where does vagus nerve collect sensory info from?
the epiglottis
Where do all taste nerves terminate?
in the rostral part of the nucleus of the solitary tract.
from the nucleus of the solitary tract, second order neurons of the cranial nerves project to
ventral posteriormedial nucleus of the thalamus
second order neurons also participate in ________ through projections to the ______.
reflex pathways involved in salivation, swallowing, and coughing, dorsal motor nucleus of the vagus (DMNX).
After the thalamus, where do the central taste pathways continue?
the taste pathways go to the frontal cortices (gustatory cortex) and then to the amygdala (fear center).
Apart from thalamus and amygdala, where else does the nucleus of the solitary tract project to?
the hypothalamus
Describe the nature of the taste pathway from the tongue to the nucleus of the solitary tract.
is ipsilateral and uncrossed.
Which channels detect salty tastes?
Amiloride-sensitive ENaCs.
What drives the activation of amiloride-sensitive ENaCs in salty taste detection?
Activation is driven by the Nernst potential based on the salt concentration in saliva.
What channels detect acidic tastes?
H+-sensitive TRP channels.
What influences the activation of H+-sensitive TRP channels in acidic taste detection?
Activation is influenced by the concentration of protons in saliva.
Which taste sensations do GPCRs detect?
GPCRs detect sweet, umami, and bitter tastes.
Name the subunits responsible for sweet taste detection by GPCRs.
T1R2, T1R3.
Name the subunits responsible for umami taste detection by GPCRs.
T1R1, T1R3.
name the subunits responsible for bitter taste detection by GPCRs.
T2RX
What occurs upon activation of a GPCR?
The GPCR promotes the exchange of GDP for GTP on the alpha subunit of the G-protein.
What happens after GPCR activation regarding the alpha subunit (Gustducin)?
The alpha subunit dissociates from the beta and gamma subunits.
What does the dissociated alpha subunit (Gustducin) do in the GPCR pathway?
The alpha subunit activates phospholipase C.
What is the role of phospholipase C in the GPCR pathway?
Phospholipase C catalyzes the conversion of PIP2 into DAG and IP3.
What happens with IP3 in the endoplasmic reticulum in the GPCR pathway?
IP3 binds and liberates Ca2+.
What does Ca2+ liberated by IP3 in the endoplasmic reticulum do in the GPCR pathway?
Ca2+ binds to and activates TRP channels, allowing for more Ca2+ influx.
How is the GPCR transduction pathway differentiated for sweet, umami, and bitter tastes?
Depending on taste (sweet, umami, or bitter), different receptors and specialized G proteins are involved.
Is it likely that each taste bud recognizes only a single tastant?
No, it is unlikely; instead, there are multiple types of taste cells within a single taste bud.
What is the function of Type I TBC in taste buds?
Involved in detecting salt; has specialized K+ leak channels for extruding intracellular K+ to the apical surface.
What tastes does Type II TBC detect, and how does it release signals?
Detects sweet, umami, and bitter tastes; releases ATP upon depolarization, interacting with P2X and P2Y afferents for postsynaptic cell activation.
What is the ATP channel on the presynaptic cell, and what happens in knockouts?
Panx1; knockouts do not prevent ATP release
Name the channels involved in mediating ATP release by Type II TBC.
CALHM1/CALHM3; channels permeable to Ca2+, mediating ATP release (KO results in no ATP release).
What is the function of Type III TBC in taste buds?
Involved in detecting sour taste; releases serotonergic vesicles activating downstream afferents and inhibiting neighboring cells for taste discrimination.
How does Type III TBC allow for discrimination between tastes?
Releases serotonergic vesicles activating downstream afferents but inhibiting neighboring cells for discrimination between tastes.
What is the purpose of Two-Photon Microendoscopy?
Used to view living neurons at depths unachievable by other techniques.
How does Two-Photon Microendoscopy measure the activity of geniculate ganglion cells?
Measures calcium expression using a fluorescent indicator, changing color upon calcium binding, indicating neuronal activity.
What was observed regarding the activation of geniculate ganglion cells in response to tastants?
Neurons are selectively activated by different tastants, and some respond to multitastants, but most are tuned to a single modality.
Is there a map in the gustatory cortex, and what does it represent?
Yes, there is a gustotopic map representing different tastants in different areas.
Why is optogenetic control used in experiments related to gustatory perception in mice?
To determine if the mouse perceives a tastant due to the activation of specific areas in the gustatory cortex rather than a higher-up process.
Describe the experimental setup involving two chambers in optogenetic control.
Mice are placed in two chambers, one with light stimulation and one without. Responses, like sweet or bitter reactions, are observed based on light stimulation.
What behavioral responses were observed when light stimulation elicited a sweet or bitter response?
When light elicited a sweet response, the mouse spent more time in the stimulated chamber. When it elicited a bitter response, the mouse spent less time there.
How were mice trained in experiments involving licking water in response to light?
Mice were trained to lick water in response to a tone. Thirsty mice, upon hearing a tone, start licking the water spout.
What does the light stimulation indicate in mice trained to lick water, and what behavioral response is observed for bitter-tasting water?
Light stimulation indicates if the water is bitter or sweet. If bitter, the mouse stops licking, even in TRPM5 knockout mice, suggesting an innate behavior.
