2b. Gustation

Question 1

how many gustatory organs do mammals have, what is it?

Answer 1

a single, tastebuds

Question 2

how many gustatory organs do insects have, where are they?

Answer 2

many distributed all over their bodies: proboscis, legs and wings.

Question 3

what does the proboscis project to

Answer 3

the sub oesophageal ganglion

Question 4

what does the legs and wings project to

Answer 4

the ventral nerve chord

Question 5

how did researchers establish separate gustatory systems for sugar and caffeine

Answer 5

transgene changes in G-CaMP fluorescence in the projections of sweet Gr5a neurons and bitter Gr66a neurons could be visualised in the SOG.

Question 6

what is the name of the receptor involved in water detection

Answer 6

pickpocket receptor

Question 7

what happens when a fly detects food

Answer 7

gustatory neurons on the legs detect the potential food. the fly stops walking and extends its proboscis.

if the food stimuli is appetitive - the proboscis extends, and ingestion occurs

if the food source is aversive - the proboscis retracts

Question 8

how many types of cells are found on each mammalian taste bud

Answer 8

4

Question 9

name the 4 types of cells found on each mammalian taste bud

Answer 9

3 types of taste-receptor cells = types 1, 2 and 3
basal cells (involved in the genesis of new TRCs)

Question 10

how is taste information conveyed to rNST (rostral nucleus of the solitary tract)

Answer 10

via cranial nerves VII, IX, X

Question 11

name 2 other regions the rNST is connected to

Answer 11

pontine parabrachial nicleus
the gustatory cortex
the lateral hypothalamus

Question 12

what does the rNST stand for lol

Answer 12

the rostral nucleus of the solitary tract

Question 13

name an innate behaviour altered by odor and taste?

Answer 13

CO2 avoidance in flies, CO2 attrition in mosquitoes, mating behaviour in flies

Question 14

describe the structure of papilla

Answer 14

in the walls of papilla are sensory cells with microvilli arranged in pit-like invaginations with accessory cells = taste buds

Question 15

do taste buds project axons to the CNS?

Answer 15

no

Question 16

how do taste buds connect to the CNS

Answer 16

taste buds are innervated bu fibres of cranial nerves VII and IX - these extend to the rNST which project to the ventral posterolateral area of the hypothalamus

Question 17

what is anosmia

Answer 17

a disruption to taste - e.g. apples taste like onions

Question 18

the human tongue has 4 modalities of taste, what are these?

Answer 18

salt, sour, bitter or sweet

Question 19

what do the 4 modalities of taste symbolise

Answer 19

distinct physiological importances

Question 20

what does sweet and sour symbolise

Answer 20

sweet = source of metabolic energy
sour = poisonous compounds

Question 21

what does sweet and sour symbolise

Answer 21

sweet = a source of metabolic energy
sour = poisonous compounds

Question 22

what does bitter and salt symbolise

Answer 22

bitter = measure of acidity
salt = sodium chloride concentration

Question 23

name the papillae associated with sour and bitter taste?
where is it found?

Answer 23

circumvallate papillae
- at the back of the tongue

Question 24

name the papillae associated with salt and sweet tastes
- where is it found?

Answer 24

fungiform papillae - found on the edges of the tongue

Question 25

Drosophila: how does water soluble taste chemicals get detected by the GRN

give an example

Answer 25

water soluble diffuse through a single pore in the sensillum to activate the neuron

sugar, salt and most amino acids

Question 26

Drosophila: how do non-water soluble taste chemicals get detected by the GRN

give an example

Answer 26

bitter hydrophobic chemicals need to rely on odourant-binding proteins to activate the GRNs

Question 27

where are OBPs expressed in taste sensilla

Answer 27

support cells

Question 28

describe the GRN housed within the sensilla

Answer 28

bipolar neuron with a cell body that lies beneath the cuticle, it extends a single axon to the SOG and a single dendrite that projects to the tip of the sensilla

Question 29

where are external taste sensilla found (3)

Answer 29

labellum
anterior wing margins
legs

Question 30

how many taste external sensilla on the labellum

Answer 30

31

Question 31

what is the evolutionary advantage of taste sensilla

Answer 31

allows the fly to sample potential food without consuming them - beneficial when encountering toxic substances

Question 32

what is the role of internal sensilla

Answer 32

allows the fly to evaluate food following ingestion before it is transferred to the digestive system

Question 33

what is the sex-specific role of taste sensilla in females

Answer 33

allows them to identify locations with preferred nutrient conditions to deposit their eggs

Question 34

what is the sex-specific role of taste sensilla in males

Answer 34

they have more of these on their legs than females - it allows them to detect non-volatile pheromones that promote courtship and mating.