Taste Lec 11

What is salt (NaCl) made of

a cation (Na⁺) and an anion (Cl⁻)

How is salty taste detected

Na⁺ activates taste receptors via epithelial sodium channels (ENaC)

Which salt tastes saltiest

sodium chloride (NaCl)

Is salty taste perception fixed

no it changes with diet (low sodium diets increase sensitivity)

What childhood experience increases later salt preference

chloride deficiency in childhood

What causes sour taste

hydrogen ions (H⁺) from acids

How is sour taste detected

H⁺ ions enter receptor cells and trigger sour perception

Why do we avoid strong acids

they can damage body tissues

Why do we like some sour foods

low concentrations are pleasant (e.g.

What evokes sweet taste

sugars like glucose fructose and sucrose

Which sugar is main energy source

glucose

Which sugar is sweeter than glucose

fructose

What is sucrose made of

glucose and fructose

How many receptors detect sweet taste

one receptor (T1R2–T1R3 heterodimer)

Do artificial sweeteners activate sweet receptors

yes

How many bitter receptors do humans have

about 25

What is a prototypical bitter substance

quinine

Can humans distinguish bitter tastes well

no most bitter tastes feel similar

Why is bitterness important evolutionarily

many bitter substances are poisonous

When is bitter sensitivity higher in women

during pregnancy

What does umami mean

savory in Japanese

What triggers umami taste

monosodium glutamate (MSG)

What taste quality is umami

brothy or meaty taste

Where is umami found naturally

meat fish mushrooms cheese tomatoes vegetables

Why is fat considered a possible sixth taste

it has receptors and produces specific sensations

What sensations does fat produce

oily creamy viscous sensations

Do humans have fat receptors

evidence suggests yes

How is fat preference learned

gut digestion creates conditioned preferences

What is the survival role of taste

to detect nutrients and harmful substances

What does bitter taste detect

potential poisons

What does sour taste detect

harmful acids

What do sweet and salty detect

essential nutrients (sugar and sodium)

What does umami detect

protein rich foods

Do infants have taste preferences

yes they are innate

Infant response to sweet taste

smiling and sucking

Infant response to sour taste

lip pursing

Infant response to bitter taste

spitting and gagging

What is specific hungers theory

nutrient deficiencies cause cravings

Which cravings are best supported

salt and sugar cravings

What is taste adaptation

reduced taste perception after constant exposure

What is cross-adaptation

one taste affects perception of another

What are PROP non-tasters

people who cannot taste PROP bitterness

What are supertasters

people highly sensitive to bitter taste with many papillae

Health impact of supertasting

it affects diet choices and may influence disease risk

What causes chili burn

capsaicin activating pain receptors

What does repeated chili exposure do

temporarily desensitizes pain receptors

What is olfaction

the sense of smell

What is gustation

the sense of taste

Why aren’t smell and taste completely separate

because flavour depends on both taste and retronasal olfaction

What is retronasal olfactory sensation

odour perception when chewing/swallowing as odorants travel from the mouth to the nose

Why does retronasal smell feel like it comes from the mouth

even though receptors are in the nose the brain perceives the sensation as originating in the mouth

What is flavour

a combination of true taste (sweet salty sour bitter umami fat) and retronasal smell

Can someone smell but not taste flavour

yes if taste is damaged smell remains but flavour is reduced or absent

What happens if the chorda tympani is anesthetized

taste is reduced or lost but smell remains intact

What is the chorda tympani

a branch of cranial nerve VII that carries taste from the front of the tongue

How does the brain process smells differently

odours are processed differently depending on whether they come from the nose or mouth

How does sweetness affect smell perception

increased sweetness enhances perceived fruit odour

What is a tastant

any stimulus that can be tasted

What are the two categories of tastants

small charged particles (salty sour) and molecules detected by GPCRs (sweet bitter)

What are taste buds

structures that generate neural signals for taste

Where are taste buds located

in papillae (bumps on the tongue)

What do taste buds contain

taste receptor cells

What are filiform papillae

structures that give the tongue its texture with no taste function

What are fungiform papillae

mushroom shaped structures with taste buds mainly at the tip and edges of the tongue

What are foliate papillae

folded structures with taste buds on the rear sides of the tongue

What are circumvallate papillae

large circular structures forming a V shape at the back of the tongue

Is the tongue map real

no taste differences exist but are minimal and all tastes are sensed across the tongue

What are microvilli in taste buds

cell membrane extensions that bind tastants

How do taste receptor cells signal

by activating taste nerves and releasing neurotransmitters like ATP

Which taste cells form synapses

type III cells

What neurotransmitter is important in taste signaling

ATP

Which nerve carries taste from the front of the tongue

chorda tympani (cranial nerve VII)

Which nerve carries taste from the middle of the tongue

glossopharyngeal nerve (cranial nerve IX)

Which nerve carries taste from the back of the tongue

vagus nerve (cranial nerve X)

What is the pathway of taste to the brain

nucleus of the solitary tract thalamus cortex (insula to orbitofrontal cortex)

What does the insular cortex do in taste

primary processing area for taste

What does the orbitofrontal cortex do

integrates taste with smell touch and temperature

What role does inhibition play in taste

helps maintain taste perception and suppress pain

Why is inhibition important for survival

it allows eating even when the mouth is injured