week 5+6+7 (gustatory) Flashcards
(33 cards)
question: which papillae are associated with which cranial nerves?
- circumvallate = CN IX glossopharyngeal
⤷ back border of tongue - fungiforme = CN VII facial
⤷ tip of tongue
explain: taste bud (function, structure)
- has the receptor cells to transduce chemicals signals after exposure to tastant
- not a neuron
⤷ considered neural epithelial cells - regenerated by basal cells
- has microvilli
name + explain: types of papillae (4)
-
circumvallate
- v shaped border
- posterior part of tongue (back border)
- least in # -
fungiform
- mushroom shaped
- around surface (scattered)
- each have 1 - 8 taste buds
- receptors for pressure and temp -
filiform
- flame shaped
- scattered across tongue
- rough surface to manipulate food
- no taste buds
- most abundant -
foliate
- leaf shaped
- lateral (sides)
- 1300 taste buds w/in the folds
name + explain: types of taste receptor cells (3)
-
type I
- glial-like functions (support)
- no recep. for tastants
- around 50% of the cells -
type II
- resp. to sweet, bitter, and umami
- 1/3 of the cells
- G-prot. coupled receptors
- no synapses with afferent fibres
- releases ATP -> activates nearby neurons -
type III
- 2 - 20% of the cells
- has synapses with afferent fibres
- can indirectly resp. to bitter, sweet, and umami bc reacts to the NT release by Type 2
- used to detect sour
question: which receptor type mediates salty?
- unsure
- possibly a type 4
question: which receptor type mediates with tastes? what mechanisms do each use?
- type 2 = sweet, bitter, umami
- type 3 = sour
- ion channels = salty, sour
- GPCR = sweet, bitter
explain: ion channel mechanism for taste
- for sour and salty
- tastant enters cell
⤷ Na+ for salty, H+ for sour - proton binds to K+ channel
- closes the K+ channel -> depolarization -> message to brain about tastant
explain: GPCR mechanism for taste
BITTER
- type 2 taste receptors (t2r)
- usually tastant = ligand containing alkaloid (ex. quinine)
- monomers or dimers
- GPCR activated
- depol. indirectly
⤷ activates phospholipase -> breaks down PIP2 into IP3 -> IP3 binds to channel to open and release Ca+ - Ca+ open and Na+ and K+ activated
⤷ increased Ca+ intracellularly
SWEET
- type 1 taste receptors (t1r)
- tastant = sugars
- heterodimers
**Ca+ causes serotonin release
⤷ for type III
**bitter uses phospholipase, PIP, IP
**sweet uses gustudin, cAMP, protein kinase
question: which cranial nerves innervate taste receptors?
- facial
- glossopharyngeal
- vagus
⤷ for throat
question: struc. of taste neurons?
- pseudounipoloar
- cell bodies in ganglia
- peripherals endings in tongue + mouth
question: does different parts of the tongue taste different flavours?
- no
- not diff. receptors for each flavour
- diff. thresholds for diff. areas -> diff. sensitivities in each area
**more sensitivite = lower threshold
question: labeled line coding vs cross fibre coding?
- labeled line/parallel processing = diff. recept. are responsible for transmitting highly specific info
⤷ aka each receptor = specialized for a taste - cross fibre = diff. qualities of a sensory modality are distinguished by pattern of nerve discharges across a large pop. of fibres
⤷ aka receptors resp. to multiple tastes so the perception is from the pattern of activity
name: evidence that taste signals are combinatorial
- some taste recep. are selectively sensitive to certain tastants
- show resp. to multiple tastants vs only resp. to one tastant
⤷ generalists vs specialists
⤷ type III (sour) = generalist, type II (sweet, bitter, umami) = specialists
explain: the combinatorial model of taste
- specialists and generalists converge onto afferent axons
- axons less sensitive
- get resp. from large # of broadly tuned neurons
⤷ so it takes the pattern of activation across the neurons (cross-fibre)
explain: order of gustatory processing in brain
- taste transmitted to cranial nerves
- nucleus of solitary tract
⤷ in medulla - project to a nucleus in the thalamus
⤷ VPMN (ventral posteromedial nucleus) - primary gustatory cortex
⤷ in frontal lobe in sylvian fissure (insula) - secondary taste cortex (for higher aspects)
⤷ sends to amygdala or hypothalamus
⤷ amyg = emotion, hypothal = motivation
question: how is label line coding supported by brain?
- cells in insular cortex (primary gustatory cortex) = preferentially sensitive to diff. tastes
define: basic taste
- any of the 4 taste qualities used to describe human taste exp.
- sweet, salty, sour, bitter
- hardwired effect to be born liking or disliking them
⤷ innate
explain: importance/purpose of each basic taste
SALT
- Na important to maintain nerve and muscle function
BITTER
- often indicate poison and toxicity
SOUR
- acids damage external and internal body tissues
SWEET
- sugar = principle energy source for humans
**taste provides info about what we should/should not ingest
⤷ nutrient = sodium and sugar
⤷ antinutrient = acid and poison
question: what is umami and fat?
UMAMI
- savouriness
- claims that it signals protein
FAT
- fatty acids = attached to a support structure
- some broken down in mouth
⤷ most in gut
question: what makes a basic taste? (how to decide/requirements?)
- receptors found in mouth
- activating the receptors leads to distinct sensations
- hardwired affect (innate)
name: support and against for umami and fatty being added to basic tastes
SUPPORT
- receptors in mouth can regulate palatability of prot. and fat
AGAINST
- proteins and fat = large molecules
⤷ mostly broken down by digestion
- have receptors for AA and fats that don’t relate to taste
- umami and fat don’t have hardwired like/dislike
- conscious sensations of fats are from somatosensory system
question: how does miraculin work?
- binds to sweet receptors
⤷ t1r2 and t1r3 - does not activate the sweet receptors
- exposure to lower pH makes miraculin activate the receptors -> sour tasting like sweet
- neutral pH = blocking sweet recep.
- acidic pH = activates sweet recep.
**acidity causes change in shape of miraculin from inhibitory to activator
define: supertaster
- indiv. whose perception of taste is themsot intense
- dep. on density and number of fungiforme papillae and genetics
question: specific hungers theory?
- missing nutrients are craved
- this theory got debunked
