Taste Flashcards
The Chemical Senses
The general chemical sense is transduced by:
Taste is primarily transduced by receptor cells within taste buds on the tongue.
These cells express a family of receptor proteins that bind families of molecules representing the standard taste categories: salt, bitter, sweet, sour and umami (glutamate).
The general chemical sense is transduced by unmyelinated somatosensory afferents present in the mouth.
Ex: Capsaicin (hot pepper ingredient). Activating these receptors on the skin would lead to a sensation of pain and heat. Activating them on the tongue leads to the sensation of “hot peppers” and is interpreted as a taste.
SARS-CoV-2 appears to be able to infect ___ cells of the ___, leading to ____ loss of taste than can be explained by loss of ___ alone
SARS-CoV-2 appears to be able to infect supporting cells of the tastebuds, leading to more loss of taste than can be explained by loss of smell alone
Types of Papillae
Mean number of taste buds = ____
Papillae create:
Mean number of taste buds = 4000
Papillae create trenches where tastants can be concentrated.
role of taste calls in avoiding or approaching food
Salty: Safe (approach) Sour: Acidi; unripe/poor nutritional value (avoid) Sweet: Nutritious (approach) Bitter: Poisonous (avoid) Umami:
Cranial Nerve VII:
Cranial Nerve IX:
Cranial Nerve X:
Cranial Nerve VII: Facial
Cranial Nerve IX: Glossopharyngeal
Cranial Nerve X: Vagus
Transduction of Taste
salty
Salty: sodium ions cross microvillus wall at specialized sites -> depolarizes cell -> action potentials generated
- transduced by a sodium channel
- influx of sodium ion
- amiloride sensitive channel
- leads to depolarization due to positive ion influx
T1R3:
T1R3: responsible for making artificial sweeteners taste “sweet”
General Sensitivity Rule-of-thumb:
General Sensitivity Rule-of-thumb:
Bitter > Sour, Salty, Sweet > Umami
Temperature vs. Sensitivity
Overall, therefore, as temperature rises, perceptions of sweetness and bitterness tend to intensify, and perceptions of sourness and saltiness tend to remain the same.
Because the effect of temperature is not uniform across compounds, it can be expected that the taste “profile” of a food will change as its temperature changes.
Cranial Nerves- Central Connections
*Cranial Nerve VII (Facial): anterior 2/3 of tongue
Central connection: nucleus solitarius (solitary nucleus)
*Cranial Nerve IX (Glossopharyngeal): posterior 1/3 of tongue
Central connection: Inferior glossopharyngeal ganglion and nucleus solitarius (solitary nucleus)
*Cranial Nerve X (Vagus): palate, epiglottis
Central connection: nucleus solitarius (solitary nucleus)
Jellybean test:
Jellybean test:
There are two jellybeans- one strawberry and one cherry
With your eyes closed and nose pinched, you will probably just guess that they are jellybeans
With your eyes open and nose pinched, you will probably narrow down your guess to some type of red fruit flavored jelly bean, but you are unlikely able to determine them to be “strawberry” and “cherry” unless you un-pinch your nose.
amygdala and taste
taste aversion
To induce conditioned taste aversions in the lab:
To induce conditioned taste aversions in the lab: apply an illness-inducing injection of lithium chloride after ingestion of a flavored solution.
T/F food can be rewarding regardless of taste
TRUE
food can be rewarding regardless of taste
***Where do the cranial nerves carrying taste information synapse in the medulla?
Solitary nucleus
**Where do the axons from the medulla (solitary nucleus) go?
VPM
the Frontal Cortex Integration of Flavor is the ?
Orbitofrontal Cortex (Frontal Cortex Integration of Flavor)
taste buds
-location
Onion-shaped structures in the mouth and pharynx that contain taste cells.
location of salty:
Towards tip to first test for nutrient content
Transduction of Taste: sour
Sour: H+ ions bind to receptor sites -> inhibit K+ pumps -> cell depolarizes and generates neural “spikes”. Corresponds to acidic strength (i.e., pH)
- influx of hydrogen ions
- TRP channel
- leads to depolarization due to positive ion influx
Transduction of Taste: the rest besides sour and salty
Sweet, Bitter, and Umami: all work through GPCRs
Ligand binds receptor -> PLC -> IP3 -> calcium fluxes in -> cell depolarizes ->action potentials
Where does the VPM send axons?
• Taste information is then relayed to the insular cortex
Orbitofrontal Cortex
-function
*Putting together things like the sight and smell of food
hypothalamus and eating
The hypothalamus knows all that goes on in your body.
It is also responsible for your feeding behaviors, so it really needs to know about what you are eating.
There is some evidence suggesting that the nervous system also reads the nutritional value of your food. This would likely require hypothalamic involvement.
Eating a bland diet –>
Eating a bland diet –>increased cravings for tasteful foods, even if nutritional needs have been met
• Sometimes called the secondary taste cortex
Orbitofrontal Cortex (Frontal Cortex Integration of Flavor)
T/F Motivational states (e.g., hunger) affect the sensitivity of cells in the insular cortex
FALSE Motivational states (e.g., hunger) do not affect the sensitivity of cells in the primary (insular) cortex.
Do motivational states (e.g., hunger) affect the sensitivity of cells in the insular cortex and/or the orbitofrontal cortex?
orbitofrontal cortex only
-motivational, emotional and learning experiences heavily influence the sensitivities of cells in the orbitofrontal cortex.
T/F regional variations in threshold/sensitivity in regards to taste buds that contains taste cells
TRUE
What do the 5 types of tastants tell us about the food? ***
2.5) What do the 5 types of tastants tell us about the food?
Sensory Coding
•Intensity: increases in stimulus concentration leads to increased firing of taste cell (depends on concentration)
what are the senses?
taste, touch, olfaction, hearing, proprioception ALSO SIGHT
where does taste info synapse?
in the insular cortex – at the rostral part of the solitary tract nucleus, which is associated with the peripheral nervous system
are taste receptor cells neurons?
NO
Taste receptor cells are NOT neurons, but they DO have action potentials and they DO release neurotransmitters
do all the sense go through the thalamus?
do all the sense go through the thalamus?
all except for olfaction
where do the cranial nerves synapse for taste?
where do the cranial nerves synapse for taste?
nucleus of the solitary tract
where does the nucleus of the solitary tract project?
where does the nucleus of the solitary tract project?
up to the thalamus, where it synapses (secondary)
what are the two main hypotheses for the processing of sensory info?
what are the two main hypotheses for the processing of sensory info?
- labeled line: wire from periphery to the cortex–specific for the given stimulus
- ensemble: receptor cells respond generally to a stimulus and that info is sent to the central nervous system
what triggers bitter and umami tastes?
what triggers bitter and umami tastes?
organic ions
what triggers sweet tastes?
sugars lol
what triggers sweet tastes?
sugars lol
insular cortex
insular cortex
- Center of taste processing - Gustatory cortex - “Very little information is available on the functional organization of insular circuits involved in taste processing.” (Maffei et al, 2013)
how can we distinguish flavors?
- olfaction is important for this purpose
- we need the interaction of smell and taste to really distinguish the flavors
- nose, nasal cavity, and tongue are positioned near each other
how can we distinguish flavors?
- olfaction is important for this purpose
- we need the interaction of smell and taste to really distinguish the flavors
- nose, nasal cavity, and tongue are positioned near each other
where are most taste buds stationed?
where are most taste buds stationed?
the tongue
-Orbitofrontal Cortex
in regards to taste
-Orbitofrontal Cortex = motivational states (hunger) do not affect the sensitivity of cells in the primary (insular) cortex.
However, motivational, emotional, and learning experiences heavily influence the sensitivities of cells in the orbitofrontal cortex.
Site of smell, taste, tactile and temperature components of flavor perception
REWARD VALUE for food
Hypothalamus
and taste
Hypothalamus
Hypothalamus helping you determine what is coming in, and whether you are hungry and not hungry
what are taste buds located within?
what are taste buds located within?
papillae
what cranial nerves are involved in taste?
what cranial nerves are involved in taste?
cranial nerve 7, 9, and 10
what do the basal cells of the taste buds allow for?
what do the basal cells of the taste buds allow for?
regeneration of taste buds
where are the tastants found and where do they interact?
where are the tastants found and where do they interact?
in the saliva, at the taste pore
what occurs when the tastants interact with taste cells?
what occurs when the tastants interact with taste cells?
taste cells transduce signals
what occurs when a cell is depolarized?
what occurs when a cell is depolarized?
allows for calcium influx or release of calcium from intracellular stores
which channels are G-protein coupled?
which channels are G-protein coupled?
sweet, bitter, umami
G protein-coupled receptors are all metabotropic receptors.
how do G-protein coupled channels function?
how do G-protein coupled channels function?
activate second messengers;
-activation of receptors and of phospholipase beta 2
-causes IP3 release
-activation of TRP M5 and calcium flux through that channel
what receptors do sweet and umami tastes use?
what receptors do sweet and umami tastes use?
transduced by the T1 receptors – sweet by T1 R2 and T1 R3, umami by T1 R1 and T1 R3
what receptors do bitter tastes use?
T2 receptor – has about 30 subunits; gustucin is involved
how do taste buds respond to individual tastes?
how do taste buds respond to individual tastes?
- only 1 or 2 tastes per cell
- cell 1 depolarizes in response to sodium, with little response to other tastes; axon 1 responds to NaCl with higher energy action potentials
- cell 2 responds to both sodium and hydrochloric acid, high energy action potentials in axon
what occurs after action potentials at the taste buds?
what occurs after action potentials at the taste buds?
release of neurotransmitters to gustatory afferent which sends signals into the central nervous system–cranial nerves 7, 9, 10
what does cranial nerve 7 carry?
what does cranial nerve 7 carry?
signals from the anterior 2/3 of the tongue
what does cranial nerve 9 carry?
what does cranial nerve 9 carry?
signals from the posterior 1/3 of the tongue
where do the cranial nerves synapse?
synapses at the gustatory portion of the nucleus of the solitary tract at the medulla pons border; secondary afferent axons project to the thalamus
are most projections to the cortex ipsilateral or contralateral?
are most projections to the cortex ipsilateral or contralateral?
ipsilateral
how are tastes arranged in the cortex?
how are tastes arranged in the cortex?
tastes are spatially arranged, spots light up in the cortex in response to a specific taste; labeled line coding–tastes remain segregated all the way up to the cortex
Impulses generated in the taste buds of the tongue reach the cerebral cortex via the
a. Thalamus
b. Hypothalamus
c. Internal capsule
d. Dorsal roots of the first cervical spinal nerves
e. Trochlear Nerve
thalamus
Diminished sense of smell in association with reproductive dysfunction is due to a deficiency of
a. Rhodopsin
b. Transducin
c. Folic Acid
d. Dopamine
e. Gonadotropin-Releasing Hormone
Gonadotropin-Releasing Hormone
In comparison with cones, rods
a. Are more common in the central retina
b. Are more involved in color vision
c. Yield a greater acuity of vision
d. Have their maximum sensitivity in bright light
e. Have a lower threshold for light
In comparison with cones, rods
Have a lower threshold for light
The largest known family of G-Protein-Coupled-Receptors are those involved in
a. Taste
b. Smell
c. Vision
d. Audition
The largest known family of G-Protein-Coupled-Receptors are those involved in
Taste
Detection of sweet, umami, and bitter tastes uses a transduction mechanism involving, as the initial step
a. Ionotropic opening of sodium channels
b. pH-sensitive cation channels
c. Metabotropic receptors
d. Release of glutamate
Detection of sweet, umami, and bitter tastes uses a transduction mechanism involving, as the initial step
Metabotropic receptors
T/F G protein-coupled receptors are all metabotropic receptors.
true
Flavor is perceived after
a. Convergence in the orbital cortex of information from multiple sources
b. Convergence of gustatory and olfactory information in the amygdala
c. Convergence of information from multiple sources in the superior colliculus
d. Convergence of gustatory information in the gustatory cortex
Flavor is perceived after
Convergence in the orbital cortex of information from multiple sources
An 8-year-old boy presents to clinic after having several months of fatigue and cold intolerance. He is found to have a TSH level of 10 mIU/mL (normal is 1), and is diagnosed with hypothyroidism. An MRI shows a moss in the suprasellar region that is likely a craniopharyngioma. Visual field examination reveals a bitemporal hemianopia. Where along the visual pathway is the most likely location for compression by the mass?
a. Both optic nerves
b. Thalamus
c. Midbrain
d. Hypothalamus
e. Optic chiasm
An 8-year-old boy presents to clinic after having several months of fatigue and cold intolerance. He is found to have a TSH level of 10 mIU/mL (normal is 1), and is diagnosed with hypothyroidism. An MRI shows a moss in the suprasellar region that is likely a craniopharyngioma. Visual field examination reveals a bitemporal hemianopia. Where along the visual pathway is the most likely location for compression by the mass?
Optic chiasm
Taste receptors
a. For sweet, sour, bitter, salt, and umami tastes are spacially separated on the surface of the tongue
b. Are synonomous with taste buds
c. Are a type of chemoreceptor
d. Are innervated by afferents in the facial, trigeminal and glossopharyngeal nerves
e. All of the above are correct
Taste receptors
Are a type of chemoreceptor
After olfactory receptor cells bind odor molecules, a sequence of intracellular events occurs that culminates in the entrance of specific ions that depolarize the olfactory receptor cell. Which ions are involved?
a. Calcium
b. Chloride
c. Hydrogen
d. Potassium
e. Sodium
After olfactory receptor cells bind odor molecules, a sequence of intracellular events occurs that culminates in the entrance of specific ions that depolarize the olfactory receptor cell. Which ions are involved?
Sodium
During a routine examination, a physician attempted to elicit a gag reflex response in a patient by stroking the posterior pharynx with a cotton-tipped swab. This reflex is initiated primarily by activating the sensory endings of
a. Cranial nerve V
b. Cranial nerve VII
c. Cranial nerve IX
d. Cranial nerve XI
e. Cranial nerve XII
Cranial nerve IX
Transduction of mechanical to neural signals occurs
a. at the base of the outer hair cells
b. at K+ channels in stereocilia
c. between the oval and round windows
d. in the scala vestibuli
e. in the scala tympani
at K+ channels in stereocilia
Information from taste receptor cells transmitted to the _____:
what nuerotransmitter is used?
Information from taste receptor cells transmitted to the CNS
No single neurotransmitter is used – serotonin, ATP, and GABA all used
Cranial Nerve VII: Facial
Cranial Nerve IX: Glossopharyngeal
Cranial Nerve X: Vagus
Cranial Nerve VII: Facial
Cranial Nerve IX: Glossopharyngeal
Cranial Nerve X: Vagus
Nonetheless, regional variations in threshold/sensitivity exist:
sweet + salty preference on anterior-third of tongue (Facial nerve)
bitter at the back of the tongue (Glossopharyngeal)
sour along back/sides of the tongue (Both Facial and Glossopharyngeal)
Nonetheless, regional variations in threshold/sensitivity exist:
sweet + salty preference on anterior-third of tongue (Facial nerve)
bitter at the back of the tongue (Glossopharyngeal)
sour along back/sides of the tongue (Both Facial and Glossopharyngeal)
what amino acids are involved in umami
Glutamate, aspartate
