Smell and Taste Flashcards

1
Q

trigeminal nerve system in the mouth

A

100-1000x less sensitive than the olfactory system

protective- detect noxious or irritating compounds

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2
Q

capsaicin receptor

A

ion channel of TRP family (also opened by heat)

capsaicin opens the TRP channel, allowing Na and Ca ions flow into the cell, causing depolarization of noiciceptive fibers and the sensation of pain/heat

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3
Q

sensitivity and discremination of olfactory system

A

10e-12 to 10e-14 M

can discriminate at least a trillion smells

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4
Q

aging effects on smell

A

by 50-70, less than 50% of our original capabilities

adds to difficulties w/ appetite and nutrition

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5
Q

anosmia

A

deficit in the ability to detect specific classes of compounds

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6
Q

odorant based communication

A

detection of sex hormones elicits sex specific responses in hypothalamus

important in mother/infant recognition

steroid component in male sweat is a pheromone, influencing arousal and mood

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7
Q

vomeronasal organ

A

pheromone receptor in the roof of the mouth- regresses during development in humans

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8
Q

gross anatomoy of the nasal cavity

A

3 ridges- conchae

most epithelium is respiratory- ciliated

olfactory receptor cells limited to upper and middle conchae

3 cell types

basal- precursor of receptor cells. average lifespan is only 60 days and complete turnover occurs every 6-8 weeks

support- apical suface w/ microvilli that support receptors

receptors- dendrites projecting to epithelial surface and unmyelinated axon that forms fascicles that eventually become the olfactory nerve before passing through the cribiform plate

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9
Q

olfactory bulb

A

contains glomeruli- endings of receptor cell axons and mitral cell dendrites

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10
Q

mitral cells

A

principal projection neurons of the olfactory bulb, and are the only ones to project to other regions of the brain

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11
Q

how do olfactory receptor neurons respond to simulation

A

change in rate at which fire APs

change is d/t change in conductance of the receptor cell that leads to its depolarization to threshold

signal transduction occurs in cilia.

odorant receptors are g protein coupled receptors w/ 7 transmembrane, which modulate ion channels in cilia

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12
Q

what mechanisms have been implicated in ordorant transduction

A

change in adenylate cyclase activity and cAMP

production of IP3 and phospholipase C

unclear if they are separate or related mechanisms

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13
Q

there is discrimination and concentration determinatino at the level of individual receptor cells

A

an olfactory receptor cell may respond to one odorant or many, and thresholds of detection may differ

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14
Q

genes encoding receptor proteins

A

nearly 1000

largest family is g protein coupled receptors- 7 transmembrane spanning regions

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15
Q

sorting of odorants

A

among receptors, there are functional groups based off molecular shape organized into different domains of expression in the nasal cavity

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16
Q

olfactory bulb convergence

A

receptor cell axons converge upon mitral cell dendrites in olfactory bulb

however, individual glomeruli are only innervated by receptors expressing the same odorant receptor

stimulation in the olfactory bulb represent identity and concentration

17
Q

cortical processing of smell

A

across fiber pattern

quality of odorant encoded in pattern of activity- pattern encodes which cells are activated and the temporal order in which they are activated

occurs in anterior piriform cortex, and neurons receive inputs from more than one glomerulus, allowing integration of receptors that sense the same stimulant

additionally, receptors exist that are only activated in the presence of multiple stimuli

18
Q

smell pathway thru the brain

A

mitral cells - piriform cortex - entorhinal cortex- hippocampus

unique because doesnt go thru thalamus on the way to cortex

info also goes to amygdala- hypothalamus

goes to thalamus- frontal cortex

19
Q

modulation of smell

A

adrenergic fibers at the olfactory bulb = heightened sense of smell during fear and excitement

input from locus ceruleus- increased sensitivity to smell of food when hungry

20
Q

5 categories of taste

A

sweet, sour, bitter, salt, umami

21
Q

hypoguesia

A

sensitivity to taste declines with age

22
Q

flavor

A

the taste combined with information from many sensory modalities, including thermo, mechano, olfactory, pain, and sight

23
Q

4 types of papillae

A

filoform- cover most of surface of the tongue- no taste buds

vallate- have 7-12 across back of tongue- 250 taste buds each- glossopharyngeal- bitter

foliate- packed folds along back edges/side of tongue- barely detectable in adults- glossopharyngeal- sour

fungiform- scattered across entire surface of the tongue- facial- sweet and salty

24
Q

supertaster

A

higher density of fungiform- increased sensitivity to bitter substance

25
Q

3 types of cells in taste buds

A

1 support cells

2 basal cells- progenitor cells that give rise to taste receptor cells

3 receptor cells- continuous turnover, average life of 10 days. no axons, secondary sensory cells

26
Q

projections from taste buds

A

go to nucleus of solitary tract, then to VPM, then gustatory cortex and hypothalamus and amygdala

27
Q

salt transduction

A

voltage insensitive sodium channels- salty food = large increase in Na concentratoin, which leaks into cells and cause depolarization

blocked by amiloride

28
Q

sour transduction

A

sour is produced by acids. protons cause a cation selective ion channel to open, resulting in depolarization

29
Q

sweet transduction

A

g protein coupled receptors for sweet molecules- causes an increases in phospholipase C, generation of IP3, and release of Ca

30
Q

miraculin

A

binds to sweet receptors under sour conditions, activating sweet when a food is sour

31
Q

bitter transduction

A

second messenger mediated, different than sweet

32
Q

umami transduction

A

metabotropic glutamate receptor linked to second messenger cascade. same as bitter

33
Q

taste receptors responds to one class of tastants. information is encoded via labelled lines and across fiber pattern

A

ok

34
Q

modulation of taste receptor cells

A

receptors for 5HT and CCK enhance taste cell

aldosterone and vasopressin enhance taste cell responses to NaCl

35
Q

synesthesia

A

stimulation of one sensory modality evokes another different modality

may be b/c excess connections b/t different regions that should have been pruned