2a. Olfaction Flashcards
why is olfaction important
allows organisms to distinguish, recognise and evaluate between food sources and dangerous substances
Odors are said to be a ‘discontinuous chemical space’, what does this mean?
they provide no spatial information to the brain
how many odorant receptor genes in mammals
1000
each olfaction sensory neuron has a single odorant receptor, where do these converge?
on the same glomerulus in the brain
what is the structure of odorant receptors in mammals
GPCR - 7 TMS
what is the structure of odorant receptors in insects
thought to be odor gated cation channels - that may be modulated by G-protein signalling f
what is the role of glomeruli
connect sensory input with output neurons and local modulatory interneurons.
these solve the problem of mapping discontinuous chemical space onto the brain.
name the key transcription factor involved in the regulation of a subset of odorant receptor genes
acj6
what are the two olfactory organs for drosophila
antenna and maxillary palp
what houses the olfactory sensory neuron found in these olfactory organs
the sensillum
what is the role of the sensillum
a sensory organ that protrudes from the cuticle of the exoskeleton
the sensillum is filled with a fluid, what does this contain
binding proteins, the odour dissolves into the fluid and binding proteins transport the odour to the odorant receptor.
what is the obligate coreceptor for olfactory neurons
Or83b
Or83b is the obligate coreceptor for all olfactory neurons except which type?
carbon dioxide sensitive neurons
what is the fancy name for the fluid bathing the sensilla
sensillar lymph
odorant binding proteins transport the solubilised chemical compound to the odorant receptor. what is the name for this mechanism?
peri-receptor events
where are odorant binding proteins found in a high concentration: insects, and vertebrates
in the nasal mucus of vertebrates
chemo-sensilla lymph of insects
what is the difference between excitatory and inhibitory projections of ORNs to the glomerulus
excitatory projections = to a single glomerulus
inhibitory projections = to multiple glomerulus
what is co-convergence
two different ORNs on the same glomeruli
what is co-expression
two different Ors on the same neuron
name a structure involved in the drosophila olfactory circuit?
mushroom bodies of the lateral horn
name the type of cell found in the mushroom bodies, where are they specifically found
Kenyon cells in the Calyx
how many glomeruli in drosophila
43 glomeruli
what are the two stages of odor discrimination
encoder stage
decoder stage
what is the encoder stage
occurs at the antenna and antennal lobe - where odors are first mapped onto the brain
what is the decoder stage
occurs in the higher brain centres, e.g. mushroom bodies. output neuron signalling is modulated by dopaminergic neurons
where is the 1 location olfactory receptors are found in mice?
the nose tissue. they only express 1 type of OR
name a higher order brain centre of a mouse
1 of:
- piriform cortex
- olfactory tubercle
- entorhinal cortex
to reach the olfactory epithelium, what must the air pass through?
the conchae
what is the difference between microsomatic and macrosomatic
humans are microsomatic animals - smell plays a small part of their sensory world. unlike dogs which are macrosomatic
what does the colour of the olfactory epithelium correspond with? give an example
the sensitivity
- in humans it is lighter yellow whereas in dogs it is dark brown
what organ is receptive to smell, especially pheremones
Jacobson’s organ
how many odorant binding proteins are currently known
52
what two molecules facilitate the detection of cVA
lush - an odorant binding protein
SNMP - a sensory neuron membrane protein
what secretes OBPs
support cells
what do males flies with a mutation to OR67d do
court male flies - prevents pheromone detection
