Physiology Of Taste And Olfaction Flashcards by Ann yo

What is anosmia?

Loss of smell

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What is augesia?

Loss of taste

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What are tastants?

Chemical compounds that bind taste receptors and impart primary flavor categories (sweet, salty, bitter, sour, umami)

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What are odorants?

Chemical compounds that bind odorant receptors that impart an odor

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What is the stimulus and NTR for

SOUR?

Stimulus: H+ ions

NTR: Serotonin

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What is the stimulus and NTR for

SALTY?

Stimulus: Na+ Binding ENaC

NTR: Serotonin

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What is the stimulus and NTR for

SWEET?

Stimulus: sugars binding GPCRs

NTR: ATP

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What is the stimulus and NTR for

UMAMI?

Stimulus: Glutamate binding mGluR4 (GPCR)

NTR: ATP

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What is the stimulus and NTR for

BITTER?

Stimulus: Various compounds binding GPCRs

NTR: ATP

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What is the strucutre of taste buds?

Specialized epithelial cells w/ distinct apical and basal domains

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What is the chemosensory transduction involved with TASTE buds?

Apical domain—> electrical signals via GPCRs to basal domain —> NTR —> local afferents —> potential AP

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Where are TASTE receptor proteins and related signaling molecules involved in chemosensory transduction concentrated?

On microvilli that emerge from apical surface of taste bud

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What does the apical surface of taste buds contain?

Voltage regulated ionchannel

Channels w/ second messengers (especially Transient receptor potential receptor family (TRP))

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What will allow the release of NTRs from the basal domain of taste buds?

Intracellular Ca release

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What kind of neurons are olfactory cells?

Bipolar neurons

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What NTR will olfactory nuerons release?

Glutamate

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What is the chemosensory transduction pathway for SMELL?

Odorant —> mucus
—> G-protein (Golf) activated
—> adenylate cyclase activated 
—> cAMP generated 
—> Cyclic nucleotide gated channels opens (CNGC) 
—> Na and Ca influx 
—> depolarization
—> Ca gated Cl channels open
—> future depolarization
—> receptor potential —> action potential

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What will cause a reduction in the magnitude of receptor potential for the chemosensory transduction of taste and smell?

Enzymatic breakdown of cAMP

Reduced affinity for channel to cAMP bc Ca binds Calmodulin

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What will elicit a robust response from odorant receptors?

Pleasant or pungent odors

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What modifies the sensitivity of odorant receptors to odorants?

Phosphorylation

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What will allow one to get “used” to a smell and no longer notice its strength?

Phosphorylation of odorant receptors

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What happens when the odorant stimuli persists?

Sensitivity of CNCG to cAMP decreases and thus reduces cation influx = no more depolarization

CNGC inactivated via receptor phosphorylation

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What happens in regards to smell during Upper Respiratory infections?

Thickened mucus blocks odorants from binding odorant receptors

= reversible hyposmia

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What is HYPERosmia seen in?

Migraine
Psychotic states
Pregnancy

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What is the evolutionary importance of “Sweet”?

Signals presence of carbs that serve as energy source

Why is taste an important sensory modality?

guides organisms to identify and consume nutrients and avoid toxins and indigestible materials

What is the evolutionary importance of “Salty”?

* Govern intake of Na and other salts | * Essential for maintaining body’s water balance and blood circulation

What is the evolutionary importance of “Umami”?

• Reflects a food’s protein content due to presence of glutamate and other AAs

What is the evolutionary importance of “sour”?

* Signals presence of dietary acids * Allows us to avoid ingesting xs acids and maintain acid-base balance for body * Many spoiled foods = acidic = avoid them

What is the evolutionary importance of “Bitter”?

* Innately aversive | * Guard against consuming poisons (many = bitter)

Characteristics of bitter-tastants associated receptor?

GPCRs w/ very high binding affinity

What is the significance of bitter-tastants’ high affinity to receptors?

Detects potential poisonous compounds at very low concentrations Allows us to avoid additional ingestion of a potentially toxic substance

What changes does gustatory sensitivity undergo as you age? Problems associated with this?

Less sensitivity to salt | Adults will add more salt and can be problematic if they have hypertension, or electrolyte/fluid problems

When do the sense of smell and taste begin?

En utero

How are infants primed for food?

Growing fetus primed to taste of amniotic fluid Amniotic fluid reflects composition of maternal diet and thus the external environment and subsequent localization of rooting for breast milk after birth

What is the common taste preference in infants?

Infants show pleasurable stimulation to sweet tastes

What effects do sweet tastes have in infants and children? How do you enact this effect?

Rapid calming effect Decreased HR Place dilute sweet solution in ORAL CAVITY (not stomach!!)

What can be used to reduce procedural pain in infants during single painful event? Examples?

Sucrose I.e. during heel lance, vein puncture, and circumcision

What is the mechanism of sucrose as an analgesic in infants?

General brain arousal —> infant distracted Sweet taste induced beta endorphin release —> endogenous opioid system activated

What tastant preference declines with age?

Sweetness

What will a more bitter medication mean?

More potent phamacological activity

How are bitter flavors masked in medicine?

Sodium salts suppress bitterness at level of RECEPTOR (MonoNa glutamate and Na Gluconate) Sugar supresses bitterness at COGNITIVE level

What is commonly added in caffeine and alcohol drinks to mask bitterness?

Sweeteners

What does the Solitary tract nucleus receive info from? Function?

From vagus nerve that relates info from viscera Reflex circuits for salivary secretions, mimetic responses, and swallowing

What is the Ventral Posterior MEdial Nucleus of the thalamus’ function for food processing?

Relay system for taste perception Discriminates taste here

What makes up the Gustatory Cortex?

Insular taste cortex Operculum of frontal lobe Post central gyrus

What is the amygdala’S role in eating?

Affective aspects Emotional context Memories of eating

What is the Hypothalamus’ role in eating?

Integration of homeostatic mechanisms of eating I.e. hunger

What is the function of the Limibc and reward system in eating?

Interplay b/w eating and calming effect of food

What is the function of the Orbitofrontal cortex in eating?

Integrates visual, somatosensory, olfaction and gustatory stimuli to collectively appreciate the FLAVOR of food

Is flavor and taste the same thing?

NO Flavor requires the integration of visual, touch, olfaction and gustation (taste)

Where does flavor perception occur?

Medial Orbitofrontal cortex

What is the pathway for gustation?

Taste buds —> geniculate, petrosal, and nodose ganglia —> solitary nucleus —> via Central tegmental tract —> Ventral posteromedial nucleus —> thru internal capsule —> Gustatory cortex (post central, frontal operculum, insula)

What is the Anterior olfactory nucleus’ function?

Relay station to ipsilateral and contralateral cortices

What is the role of the piriform cortex and lateral hypothalamus in olfaction?

Controls appetite Controls how olfactory input influences appetite and hunger

What is the role of the piriform cortex and MEDIAL Orbitofrontal cortex?

Integrates sight, smell, and taste of food | Appreciate FLAVOR of food

What is the role of the Anterior Cortical Amygdaloid nuclei in olfaction?

Integrates emotional aspect of food as elicited by odor

What is the function of the ENtorhinal cortex and hippocampus in olfaction?

Forms memory based on olfactory input | Connections w/ Limbic system allow for recall of memory upon odor sensation

What is the first pathology demonstrated in Parkinson disease?

Neurons of olfactory system degenerate Early sign = loss of smell

What is pathway from olfactory neurons to lateral olfactory tract?

Olfactory neurons —> release glutamate at glomeruli —> periglomerular cells activated, release GABA = allows for increase in specificity of signal —> Mitral/Tufted cells project to olfactory tract —> granular cells release GABA and further increase specificity of signal as it goes to... —> Lateral olfactory tract