6. Taste Flashcards
The evolution of the human brain
• Brains got bigger, evolution/biology haven't really changed; \_\_\_\_ and \_\_\_\_ fundamental to all biology ○ Food- need to survive ○ Sex- species dies out if you don't have offspring
food
sex
• Taste receptors reside on the tongue and on back of throat (phaynx)
○ Pharynx doesn’t give rise to ____ taste, along with others
• Take hop and squeeze juice, chemicals inhibit bacteria and control the growth of beer
○ ____- stimulates bitter taste receptors that reside on pharynx
• Not on cheeks, not under tongue, not under lips, not on hard palate, but they ARE on ____
• Anterior 2/3 tongue - chorda tympani nerve, branch of the trigeminal
○ What most people think what we taste with
○ Have as many taste buds on ____ as aneitre 2/3 of tongue
○ Soft palate innervated by ____ (greater superficial petrosal)
• Posterior 1/3 tongue - ____, branch of it
• On tongue - the taste bud (cannot seen naked eye) lives on papillae
• On soft palate/pharynx - live in ____ on buds (no papillae)
conscious isohumolones soft palate SP VII glossopharyngeal smooth epithelium
Each taste papillae contains many taste buds, each of which contain many taste cells
BUT: large individual variability in both the number of taste papilla and the number of taste buds within a papillae
• \_\_\_\_ cells; a micro-organ (similar to an eye/retina) • On smooth epi or speicalized bumps • Specialized epi cell (not \_\_\_\_, unlike receptor cells in olfactory they're actually neurons), but they act like neurons (\_\_\_\_ active) ○ Not derived from same tissue as \_\_\_\_ tissue, and have no axons ○ Can have potentials ○ Have \_\_\_\_; communicate with neurons (synaptically or non-synaptically) • On end of tongue > two kinds of papillae > \_\_\_\_ (toadstolls, mushroom), and \_\_\_\_ (smaller); TB reside with \_\_\_\_, but not within \_\_\_\_; have on \_\_\_\_ surface anterior 2/3 ○ Filliform make tongue \_\_\_\_ ○ Fungiform not evenly \_\_\_\_; most densely on \_\_\_\_ and edges, very few in middle; the ones in middle have limited \_\_\_\_ • As you get further back > \_\_\_\_ (leaves) and \_\_\_\_ papilla (exist in all \_\_\_\_, in humans = circumvalle, look like tower with moat surrounding) ○ In both cases, the invagination where the moat is, is where the \_\_\_\_ resides; down live within gill slits
80-100 neural tissue electrically neural NT fungiform filliform fungiform filliform dorsal
rough
distributed
tip
TB
foliate
valle
mammals
TB
T1R and T2R Expression Sites
• Throughout entire ____, and all major ____ organs
○ Stomach, intestine
• Have in ____ (on beta islet cells- responding to nutrients and releasing insulin)
• Have in liver
• Also in ____, thyroid and in lungs
• We’re not ____ of any of these
GI metabolic pancreas brain conscious
• A micro-organ, ____ cells within
• A hole in epi that we call ____ > whatever you put in mouth will have access into these cells > penetrate thru epi and into contents of oral cavity
• ____ - open to oral cavity, need to limit what gets into epithelium
• Cells are fairly ____
○ Main class - Type I/II/III
§ II- respond to for ____
□ Umami: MSG illicits (____)
□ Foods naturally high in free glutamate: ____, mushrooms, ____, corn, ____
□ If you destroy protein with high glutamate - break it down (ferment/cook)
□ Highest free glutamate containing food: ____ (highest MSG)
§ I/III- unknown, III may do ____, I may be ____ cell (like glial)
§ Can be ____ active, but cannot send signals to brain only through ____ (synaptically and non-synaptically)
• From TJ above > ____ end of cell; below the TJ > ____
80-100 cells taste pore tight junctions homogenous sweet/bitter/savory/umami glutamate shellfish tomatoes green peas pizza
sour/salt
support
electrically
neurons
apical
basolateral
Taste Buds Are Complex Structures
• Each bud contains ____ to >____ cells.
• Several distinct morphological and functional types.
• ____ interactions among cells.
• Cells continually ____ throughout life.
• Mediate responses to variety of chemicals.
• ____ taste qualities in most mammals. – Sweet, sour, salty, bitter and umami.
• All chem senstiive tissues in body > tissues both undergo continuous replacement via cells, and they are \_\_\_\_ tissues ○ Cells naturally undergo \_\_\_\_ (exc those in brain/heart) § Olf tissue - neurons die off constantly - comm directly to CNS ○ Regenerative- remove organ - it'll grow back; humans do not regrow (lobsters and lizards do) § We do have regenerative tissues - \_\_\_\_: olf epithleiulm (nasal), taste buds (dorsal of tnogue), tips fingers/toes, lining of gut, the liver, and ears
50 100 laterally replaced five
regenerative
apoptosis
chemosensory
How are taste cells characterized
How Are Taste Cells Characterized? • Morphological and fine structural features – \_\_\_\_ density – \_\_\_\_ extensions – Profile of \_\_\_\_ – \_\_\_\_ connections
• Molecular features
– ____
– Transduction components – Synaptic ____
• Functional responses to stimuli
– ____ recordings
– Functional ____
– ____ responses
• Differences in shape, molecules expressed, and how they function
cytoplasmic
aplical
nucleus
synaptic
receptors
proteins
electrophysiological
imaging
calcium
Morpholoigcal Types Differ in Functional Properties
• I > II > III • \_\_\_\_ (extend into oral cavity); not cilia (like olfactory neurons - defined entitiy ilke crystal structure) ○ I- have \_\_\_\_ tall ○ II- \_\_\_\_ ones ○ III- one \_\_\_\_ one • Shapes of cells ○ Cell is rodshaped or gets fat; nucleus is oval or round; and in cross-section, shape of overal cell in nucelus ○ II- (bitter/sweet/savory/umami) : \_\_\_\_, nuc in \_\_\_\_, and round cell and nucleus > nucleus is \_\_\_\_ ○ III- skinnier and \_\_\_\_ spindle; nucles is \_\_\_\_, cut in half squished sausage ○ I- \_\_\_\_-shaped nucleus, cut in half have "\_\_\_\_" > shaped like a manta-ray (thick body and wings outward); hug cells around them > provide \_\_\_\_ and \_\_\_\_ supoprt; help maintain the environments around them
microvilli
large
little
big
elongated
middle
spherical
elongated
oval
egg
wings
structural
ionic
Sweet, umami and bitter receptors are GPCRs
Salt and sour receptors are unknown, but likely ____ channels
Umami receptor is a heterodimer of ____ + ____
Sweet receptor is a heterodimer of ____ + ____
Bitter receptors are ____ of about 25-35 types and may function as ____
Sour (acid) receptors are shown as a ____ channel. This is not established. ____ channels have also been implicated in sour taste.
All the Salt receptors have not been identified, but ____ channels are important.
ion T1R1 T1R3 T1R2 T1R3 T2Rs heterodimers PKD2L1 TRP ASIC ENaC
• Both iono and metabo receptors
○ Don’t know all ionic; ionic stimulie (NaCl for salty, and acid for sour); for sour, dissociated ____; ions are getting in cell (Na+, H+) and depolarize the cell, goes directly into cell from mouth
○ Sweet/bbitter umaimi - ____ - GPCR (7 TM) - different classes, classified by how big EC terminus is
§ Class ____ (T1R1, T1R2, T1R3) > form heterdimers; common fro GPCR to partner up with identical (homomer/dimer/multimer)
§ Sweet: heteromer of T1R2/T1R3
□ Glutamate/ribonucletodies (inosine and guanosine (IMP, GMP)), likes ____ and ____ there at same time
□ Detector of ____ and cooking
§ Savory/umami: T1R1/T1R3
□ Must have ____ to be fxnal
□ Sugar/high potency sweetener activate this (???)
§ Bitter comes from ____ (many more than just 3, over 30 of them, most have been ____ (cannot make fxnal transcript, 25 are fxnal); receptors are ____, don’t work equally well > differences among all of us
• Sour - ____ channels - do not know what’s responible - acid-sensing ion channel (ASIC) may be involved
• Salty - good idea that it’s an epi ____ channel (present everywhere in epi), but taste tissue is within epithelium (____in taste tissue, expressed in gut/lung/kidney - use ____ (diuretic and is an ENaC blocker); in kidney, reabsorb sodium causes retnetion of water, if can’t resorb Na cannot retain water - if ENaC resposniebl for salt - rinse mouth with imilleride and if taste salty it shouldn’t taste ____; ENaC also expressed in ____
H+
metabo
I
IMP
glutamate
fermentation
both
T2R
pseudogenized
ion
sodium ENaC imilleride salty taste cells
Sweet taste receptor
• T1R____
• Large ____ termini
• Conformational change when activated, casues EC cup sshape to bend over and close
○ ____ shell, venus fly trap
• If sugar (fruc/gluc) > activate, conformational change and it’ll close in on it > changes thrugohout protein that results ina ctivations that will allow when bumps into ____ to be activated and into two pieces alpha and B/gamma taste
• For ____, and sweet/savory > these is what’s happening
2/3 EC clam G-protein bitter
Model of GPCR mediated taste cell responses
• Downstream from activation • G protein activated, and activates \_\_\_\_ (not transmemberna, but floats with bilayer, lives in thing it chews up) > cuts up phospholipids (PIP2) into \_\_\_\_ and \_\_\_\_ ○ \_\_\_\_ is the second messenger here (taste can also do cAMP) ○ IP3 goes to a IP3 receptor and causes ion channels to open ○ Unlike CNGC (on cell membrane), allow ions from outisde to come in ○ IP3 goes to closet, and lets all ions spill into cytoplasm from the \_\_\_\_ (lots of \_\_\_\_); ion channels involving IP3 gating § Ca++ also in olfaction (from outside to in), but in taste goes from ER to cytoplasm • Initiate electrical activation of cell - \_\_\_\_ step ○ Olf - Ca++ increase > acts on Cl- channel (Ca++ gated), and leaves the cell ○ Taste - Ca++ acts on \_\_\_\_ (impt for pain, and burning/menthol) > \_\_\_\_ enters (this is the amplifcation) > full blown depolarization • \_\_\_\_ gated ion channels open • Depolar causes vesicles containing \_\_\_\_ (for sweet/bitter/umami, Type II) > goes through a \_\_\_\_ (related to channels forming TJ, but half a channel, openable pore in sdie of membrane) > cell-to-cell signaling molecule; here's its \_\_\_\_ communication; purinergic receptors (P2X) on neruons, so when ATP released it acts on neurons and it will spike (not synaptic connection!, much larger here, ATP has to \_\_\_\_ from one cell to another, much \_\_\_\_ than with an actual synpatic cleft)
PLC IP3 DAG IP3 ER Ca++
amplification TRP Na+ voltage ATP
hemichannel
intercellular
float
slower
Taste Transduction
• ____ Receptors
– Stimuli act directly on ion channels in apical membrane.
• ____ Receptors
– Receptors coupled indirectly to taste cell activation via G-proteins
ionotropic
metabotropic
- ____- first CNS synapse occurs
- Cell bodies reside in periphery - ____
- Peripheral cell comm with cell within TB > projecting into BS > ____(____ area of nucleus)
brainstem
ganglia
solitary tract
rostral
• Play with genes in mice, and delete gene
• WT mouse, stimulate with chemicals that are savory (AA, sugar, toxin [bitterness- if chemical is ____ soluble it will be bitter; all meds are toxins (doses makes it helpful)]
• T1R1 > KO > affect the heterodimer T1R1/3 > umami > don’t repsond to ____, but respond same to else
• T1R2 KO > affect 2/3 heterome > sweet > can taste umami, but not ____
• T1R3 KO > 1/3, and 2/3 > doesn’t respond to ____ or ____, but bitter/sour/salty is okay
• T2R5 KO (cyclohexamide toxin) > no longer ____
• PKD (TRP channel, causes poly cystic kidney disease) > marker of cells that when stim with acids the cells become ____ active (not the sour taste receptor, but it is a marker) > can kill cell type in body if you know genetic marker > can link ____ > anywhere this gene is express it’ll make DTA and kill it > can’t taste anything sour bc it killed all those cells
• Downstream, the enzyme responsible for IP3 is PL > can be tissue-specific
○ ____ (taste) KO > activated by G-protein > KO all metabotropic taste (not sweet/bitter//umai), but you get ____ (sour, salty)
○ Amplicaition (the Ca+ gated ____) > ____ cells don’t work, iono is fine
• Shown that you can’t KO ____ bc organism doesn’t grow - ____ KO in a specfici tissue, and from mouth > have trouble tasting ____
water AA sweet AA sugar responds
electrically diptheria toxin (DTA)
PLB2
TRPM5
metabo
EnAC
conditional
salt
