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Neuro Exam 3 > 4. Physiology taste & olfaction > Flashcards

4. Physiology taste & olfaction Flashcards

1
Q

Anosmia

A

loss of sense of smell

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2
Q

Aguesia

A

loss of sense of taste

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3
Q

what are tastants

A

the chemical compounds that bind taste receptors and impart the primary flavor categories (sweet, salty, bitter, sour, unami)

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4
Q

what are odorants

A

the chemical compounds that bind odorant receptors that impart an odor

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5
Q

what are taste buds

& how do they work

A

specialized epithelial cells w/ apical & basal domain

Chemosensory transduction in apical domain & electrical signals generated at the basal domain via graded receptor potentials –> release NT.

  1. Taste receptor proteins and related signaling molecules are concentrated on the microvilli from apical surface. –> Vg ion channels & second messengers (TRP) .
  2. Intracellular Ca release –> synaptic vesicle fusion & release NT in basal synapse w/ local afferents
  3. activation of the afferents–> receptor potential if large enough –> AP
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6
Q

characteristics of sour tast

A

stimulated by H+ ions

NT = 5-HT

  • presence of dietary acids. (aversive, avoid ingesting excess acids and overloading the mechanisms that maintain acid–base balance for the body) - spoiled food tastes sour
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7
Q

characteristic of salty

A

stimulated by Na binding ENaC

NT = 5-HT

intake of Na+ and other salts, essential for maintaining the body’s water balance and blood circulation.

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8
Q

characteristics of sweet taste

A

stimulus = sugars binding GPCRs

NT = ATP

foods signal the presence of carbohydrates that serve as an energy source

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9
Q

Umami taste characteristics

A

stimulated by Glu binding mGluR4

NT = ATP

  • reflect a food’s protein content due to the presence of glutamate and a few other amino acids.
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10
Q

bitter taste characteristics

A

stimulated by various compounds binding GPCRs

NT = ATP

-innately aversive = guard against consuming poisons,(= bitter to humans) bitter-tuned GPCRs bind ligand with very high binding affinity ==> potentially poisonous compounds detected at very low concentration to avoid ingestion

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11
Q

how does sensory transduction of olfactory neurons occur

A

olfactory cells = bipolar - release Glu

  1. odorant bind receptor in membrane of cilia in mucosa
  2. activate Golf –> activate adenylyl cyclase –> increase cAMP
  3. cAMP opens cyclic nucleotide gated channels (CNGC) –> influx Na & Ca –> depol
  4. –> open Ca gated Cl channels –> remainder of depol
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12
Q

what occurs if odorant stimulation persists

A
  1. 1) sensitivity of the CNGC to cAMP decreases, reducing cation influx
  2. 2) is inactivated by receptor phosphorylation (desensitization)–> “get used to” (Adaptation)
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13
Q

why cant you taste food when you have a cold

A

Thickened mucus blocks odorants from binding the odorant receptors

–> example of r_eversible hyposmia._

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14
Q

what is hyperosmia

A

HYPERosmia has been identified in migraine, psychotic states, and pregnancy

heightened smell

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15
Q

what happens to taste & olfaction with age

A

declines with age

-add more salt to food –> can lead to HTN, electrolyte &/or fluid problems

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16
Q

when is gustation & olfaction sensitivity high

A

childhood

smell & taste begin in utero –> reflect maternal diet & rooting for breast milk after birth

17
Q

what happens when you present sweet to newborn/infant

A

-face relaxes, imaging shows patterns of pleasure, calming effect w/ decreased HR

analgesic in infants & children for minor/painful procedures

18
Q

how is sweet related to analgesic effects

A

postnatal rats –> activate descending pain modulation centers (PAG & raphe nuclei)

sweet taste induce beta-endorphin release, activating endogenous opiod system

19
Q

how can bitter flavor be masked

A

sodium salts (monosodium glu & sodium gluconate) suppress lecel of bitter-receptor

sugar suppress bitterness at cognitive level

20
Q

what is the role of nucleus of solitary tract

A
  1. receives multiple sensory inputs from CN X that relays information about the viscera.
  2. Early site of gustatory and visceral information.
  3. Reflex circuits forms basis for salivary secretions, mimetic responses and swallowing.
21
Q

what is the role of VPM of thalamus

A

relay station for taste perception.

process discriminative aspects of taste

22
Q

what makes up the gustatory cortex

A

Insular taste cortex, operculum of the frontal lobe, post-central gyrus

23
Q

what is the role of hypothalamus & amygdala in taste

A
  1. Amygdala: Affective aspects of eating, emotional context & memories of eating
  2. Hypothalamus: Integrate homeostatic mechanisms of eating like hunger
  3. Interplay between eating and the calming effects of food take place in the limbic and reward system.
24
Q

what is the role of orbitofrontal cortex in taste

A

Integrating visual, somatosensory, olfaction and gustatory stimuli to collectively appreciate the flavor of food

(note: taste and flavor are not interchangeable terms).

25
Q

how does ant olfactory nucleus play into olfaction

A
  1. Relay station to ipsi- and contralateral cortices
26
Q

what is the role of piriform cortex & lateral hypothalamus in olfaction

A
  • control of appetite
  • control how olfactory input influences appetite and hunger.
27
Q

what is the role of piriform cortex & medial orbitofrontal cortex in olfaction

A
  1. integration of sight, smell, and taste of food.
  2. Appreciation of the flavor of food
28
Q

how does ant cortical amygdaloid nuclei play into olfaction

A

emotional learning, olfactory fear conditioning

29
Q

what is the role of periamygdaloid cortex

A

integrates the emotional aspect of food as elicitied by odor.

30
Q

how does the entorhinal cortex & hippocampus play into olfaction

A
  • memory formation
  • how olfactory input facilitates both memory and recall.
  • highly evocative experience of memory upon odor sensation
31
Q

olfactory impairment could be signs of

A

neurodegenerative diseases

-seen in parkinson’s pts

Neuro Exam 3 (16 decks)

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