2b. Gustation Flashcards
how many gustatory organs do mammals have, what is it?
a single, tastebuds
how many gustatory organs do insects have, where are they?
many distributed all over their bodies: proboscis, legs and wings.
what does the proboscis project to
the sub oesophageal ganglion
what does the legs and wings project to
the ventral nerve chord
how did researchers establish separate gustatory systems for sugar and caffeine
transgene changes in G-CaMP fluorescence in the projections of sweet Gr5a neurons and bitter Gr66a neurons could be visualised in the SOG.
what is the name of the receptor involved in water detection
pickpocket receptor
what happens when a fly detects food
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
how many types of cells are found on each mammalian taste bud
4
name the 4 types of cells found on each mammalian taste bud
3 types of taste-receptor cells = types 1, 2 and 3
basal cells (involved in the genesis of new TRCs)
how is taste information conveyed to rNST (rostral nucleus of the solitary tract)
via cranial nerves VII, IX, X
name 2 other regions the rNST is connected to
pontine parabrachial nicleus
the gustatory cortex
the lateral hypothalamus
what does the rNST stand for lol
the rostral nucleus of the solitary tract
name an innate behaviour altered by odor and taste?
CO2 avoidance in flies, CO2 attrition in mosquitoes, mating behaviour in flies
describe the structure of papilla
in the walls of papilla are sensory cells with microvilli arranged in pit-like invaginations with accessory cells = taste buds
do taste buds project axons to the CNS?
no
how do taste buds connect to the CNS
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
what is anosmia
a disruption to taste - e.g. apples taste like onions
the human tongue has 4 modalities of taste, what are these?
salt, sour, bitter or sweet
what do the 4 modalities of taste symbolise
distinct physiological importances
what does sweet and sour symbolise
sweet = source of metabolic energy
sour = poisonous compounds
what does sweet and sour symbolise
sweet = a source of metabolic energy
sour = poisonous compounds
what does bitter and salt symbolise
bitter = measure of acidity
salt = sodium chloride concentration
name the papillae associated with sour and bitter taste?
where is it found?
circumvallate papillae
- at the back of the tongue
name the papillae associated with salt and sweet tastes
- where is it found?
fungiform papillae - found on the edges of the tongue
Drosophila: how does water soluble taste chemicals get detected by the GRN
give an example
water soluble diffuse through a single pore in the sensillum to activate the neuron
sugar, salt and most amino acids
Drosophila: how do non-water soluble taste chemicals get detected by the GRN
give an example
bitter hydrophobic chemicals need to rely on odourant-binding proteins to activate the GRNs
where are OBPs expressed in taste sensilla
support cells
describe the GRN housed within the sensilla
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
where are external taste sensilla found (3)
labellum
anterior wing margins
legs
how many taste external sensilla on the labellum
31
what is the evolutionary advantage of taste sensilla
allows the fly to sample potential food without consuming them - beneficial when encountering toxic substances
what is the role of internal sensilla
allows the fly to evaluate food following ingestion before it is transferred to the digestive system
what is the sex-specific role of taste sensilla in females
allows them to identify locations with preferred nutrient conditions to deposit their eggs
what is the sex-specific role of taste sensilla in males
they have more of these on their legs than females - it allows them to detect non-volatile pheromones that promote courtship and mating.
