2a. Olfaction

Question 1

why is olfaction important

Answer 1

allows organisms to distinguish, recognise and evaluate between food sources and dangerous substances

Question 2

Odors are said to be a ‘discontinuous chemical space’, what does this mean?

Answer 2

they provide no spatial information to the brain

Question 3

how many odorant receptor genes in mammals

Answer 3

1000

Question 4

each olfaction sensory neuron has a single odorant receptor, where do these converge?

Answer 4

on the same glomerulus in the brain

Question 5

what is the structure of odorant receptors in mammals

Answer 5

GPCR - 7 TMS

Question 6

what is the structure of odorant receptors in insects

Answer 6

thought to be odor gated cation channels - that may be modulated by G-protein signalling f

Question 7

what is the role of glomeruli

Answer 7

connect sensory input with output neurons and local modulatory interneurons.

these solve the problem of mapping discontinuous chemical space onto the brain.

Question 8

name the key transcription factor involved in the regulation of a subset of odorant receptor genes

Answer 8

acj6

Question 9

what are the two olfactory organs for drosophila

Answer 9

antenna and maxillary palp

Question 10

what houses the olfactory sensory neuron found in these olfactory organs

Answer 10

the sensillum

Question 11

what is the role of the sensillum

Answer 11

a sensory organ that protrudes from the cuticle of the exoskeleton

Question 12

the sensillum is filled with a fluid, what does this contain

Answer 12

binding proteins, the odour dissolves into the fluid and binding proteins transport the odour to the odorant receptor.

Question 13

what is the obligate coreceptor for olfactory neurons

Answer 13

Or83b

Question 14

Or83b is the obligate coreceptor for all olfactory neurons except which type?

Answer 14

carbon dioxide sensitive neurons

Question 15

what is the fancy name for the fluid bathing the sensilla

Answer 15

sensillar lymph

Question 16

odorant binding proteins transport the solubilised chemical compound to the odorant receptor. what is the name for this mechanism?

Answer 16

peri-receptor events

Question 17

where are odorant binding proteins found in a high concentration: insects, and vertebrates

Answer 17

in the nasal mucus of vertebrates
chemo-sensilla lymph of insects

Question 18

what is the difference between excitatory and inhibitory projections of ORNs to the glomerulus

Answer 18

excitatory projections = to a single glomerulus
inhibitory projections = to multiple glomerulus

Question 19

what is co-convergence

Answer 19

two different ORNs on the same glomeruli

Question 20

what is co-expression

Answer 20

two different Ors on the same neuron

Question 21

name a structure involved in the drosophila olfactory circuit?

Answer 21

mushroom bodies of the lateral horn

Question 22

name the type of cell found in the mushroom bodies, where are they specifically found

Answer 22

Kenyon cells in the Calyx

Question 23

how many glomeruli in drosophila

Answer 23

43 glomeruli

Question 24

what are the two stages of odor discrimination

Answer 24

encoder stage
decoder stage

Question 25

what is the encoder stage

Answer 25

occurs at the antenna and antennal lobe - where odors are first mapped onto the brain

Question 26

what is the decoder stage

Answer 26

occurs in the higher brain centres, e.g. mushroom bodies. output neuron signalling is modulated by dopaminergic neurons

Question 27

where is the 1 location olfactory receptors are found in mice?

Answer 27

the nose tissue. they only express 1 type of OR

Question 28

name a higher order brain centre of a mouse

Answer 28

1 of:

• piriform cortex
• olfactory tubercle
• entorhinal cortex

Question 29

to reach the olfactory epithelium, what must the air pass through?

Answer 29

the conchae

Question 30

what is the difference between microsomatic and macrosomatic

Answer 30

humans are microsomatic animals - smell plays a small part of their sensory world. unlike dogs which are macrosomatic

Question 31

what does the colour of the olfactory epithelium correspond with? give an example

Answer 31

the sensitivity
- in humans it is lighter yellow whereas in dogs it is dark brown

Question 32

what organ is receptive to smell, especially pheremones

Answer 32

Jacobson’s organ

Question 33

how many odorant binding proteins are currently known

Answer 33

52

Question 34

what two molecules facilitate the detection of cVA

Answer 34

lush - an odorant binding protein
SNMP - a sensory neuron membrane protein

Question 35

what secretes OBPs

Answer 35

support cells

Question 36

what do males flies with a mutation to OR67d do

Answer 36

court male flies - prevents pheromone detection