Taste

Question 1

Stimulus of Taste

Answer 1

chemicals sensed by chemoreceptors

Question 2

Where are taste receptors?

Answer 2

tongue, palate, pharynx and epiglottis

Question 3

Papillae

Answer 3

folds in epithelium

Question 4

Sweet stimulus

Answer 4

sugar

Question 5

Sour stimulus

Answer 5

acid

Question 6

Salty stimulus

Answer 6

sodium (NaCl)

Question 7

Bitter stimulus

Answer 7

alkaloids (e.g. coffee)

Question 8

Umami stimulus

Answer 8

amino acids - especially glutamate

Question 9

How many cells in a taste bud?

Answer 9

50-100 columnar epithelial cells (type I, II and III)

Question 10

What tastes activate Type I receptors?

Answer 10

not involved in taste, help to maintain homeostasis of the taste bud

Question 11

What tastes activate Type II receptors?

Answer 11

sweet, bitter and umami

Question 12

What tastes activate Type III receptors?

Answer 12

sour and salty

Question 13

What happens after tastant interacts with receptor?

Answer 13

Ca2+ influx into the cell

Question 14

What does Ca2+ influx cause?

Answer 14

Release of neurotransmitter or signalling molecule that interacts with an afferent nerve fibre

Question 15

Transduction Mechanism neurotransmitters (4)

Answer 15

ATP
GABA
Serotonin
Ach

Question 16

Type II taste cell G-protein mediated signalling

Answer 16

Gq protein pathway: phospholipase C

Question 17

Sugar receptor

Answer 17

Type I homodimer

on Type II cell

Question 18

Umami receptor

Answer 18

Type I heterodimer (on Type II cell)

Question 19

Bitter receptor

Answer 19

Type II monomer (on Type II cell)

Question 20

Otop1

Answer 20

Sour

Question 21

ENaC

Answer 21

Salt

Question 22

Capsaicin

Answer 22

Active componant of chillis

Question 23

Piperine

Answer 23

alkaloid that gives pepper its pungency

Question 24

Astringent foods

Answer 24

High amounts of tannins, causes contraction of mucus layers in mouth leaving mouth dry
- popcorn, unripened bananas, pomegranates

Question 25

CD36

Answer 25

fatty acid receptor

Question 26

Sour transduction pathway

Answer 26

When an acid interacts with a type III taste cell, proton influx via OTOP 1, pH decreases (more acidic)depolarises cell, blocks the leaky K+ channel and stops K+ from leaving, leading to depolarisation, opening voltage gated Na+ channel, influx of Na+ leading to an action potential, which opens the Ca2+ channels and we get an influx of Ca2+, which leads to the release of vesicles containing neurotransmitters to be released onto afferent nerve fibres

Question 27

Salt transduction pathway

Answer 27

Na enters cells through ENaC ( Epithelial Sodium Channel) causing depolarisation, opening voltage gated calcium channels, Ca comes in and cause release of neurotransmitters onto afferent nerve fibres

Question 28

Taste bud innervation (4)

Answer 28

Chorda tympani Lingual Trigeminal Glossopharyngeal

Question 29

Motor nerve to tongue muscle isn mainly:

Answer 29

Hypoglossal

Question 30

Taste signal transduction pathway

Answer 30

Afferent fibres -> medulla -> thalamus -> cortex

Question 31

Aguesia

Answer 31

Total loss of taste

Question 32

Dysguesia

Answer 32

Persistent horrible taste in mouth

Question 33

Hyperguesia

Answer 33

Partial loss of one type of taste

Question 34

What causes a decrease in pH / influx of protons into Type III sour receptor cells?

Answer 34

Acid interaction / sour

Question 35

What does a decrease in pH in /influx of protons into Type III receptor cells result in?

Answer 35

Blocking of leaky K+ channels

Question 36

What happens when leaky K+ channels are blocked?

Answer 36

Depolarisation of cell

Question 37

What happens when the cell depolarises from blocking K+ channels?

Answer 37

Opens Na+ channels

Question 38

What does the opening of Na+ channels cause?

Answer 38

Firing of action potentials and opening of Ca2+ channels

Question 39

Which cells are G-protein mediated?

Answer 39

Type II taste cells