Did olfaction evolve separately in vertebrates and invertebrates?
Yes!
Gustatory is the sense of _____.
Taste
In insects, where are the olfactory organs?
On antenna or antennules
What are the antenna and antennules of insects covered with?
Sensilla, hairlike projections of the cuticle
What are the two proposed mechanisms for olfaction reception in flies?
- ionotropic
- metabotropic
How do worms “smell”?
Using their amphid sensory organ
Where is the olfactory organ located in vertebrates?
The roof of the nasal cavity
Are olfactory receptor cells in vertebrates multipolar neurons?
No they are bipolar neurons. One end in the olfactory epithelia layer and the other passes through the bony cribiorm plate to synapse with neurons in olfactory bulb in the brain.
How is the outer surface of olfactory receptor neurons in vertebrates is highly modified?
- covered in cilie that project into the mucus layer (increase surface area)
- cilia are non-motile
- cilia contain odorant receptor proteins
Describe how we smell?
- Odourants bing to receptors
- Olfactory receptor cells are activated and send electric signals
- The signals are relayed in glomeruli
- The signals are transmitted to higher regions of the brain
Describe signal transduction in vertebrate olfaction.
- GPCR
- cAMP pathway
- opens cyclic nucleotide-gated calcium channels (CNGC)
- influx of Ca2+
- opens calcium activates chloride channels (CaCC)
- efflux of Cl-
- depolarization
What are the mechanisms of inactivation of olfaction pathways?
- receptor phosphorylatoin by protein kinase A
- inhibition of AC by Ca-calmodulin-dependent kinase
- hydrolysis of cAMP by PDE
- removal of Ca by Ca-Na exchanger
Can one odorant can excite more than one neuron?
Yes!
What is the unique plasticity of vertebtrate olfactory sensory neurons?
- most sensory systems are limited and fixed number of receptors
- odor receptors undergo constant renewal, being replaced every 6-10 weeks
- population of olfactory stem cells
- 10,000-30,000 new olfactory neurons per day
What are pheromones?
Chemical signals released by one animal that affet the behaviour of another animal of the same species
- maintenance of social heirarchies
- stimulation of reproduction
What is the pheromone sense organ?
The vomeronasal organ - structurally and molecularly distinct from primary olfactory epithelium.
Where is the VNO located in mammals?
Near the base of the nasal cavity near the septum.
Where is the VNO located in reptiles?
On the palate with a narrow tube connecting to either the nasal or oral cavity.
Pheromones activate which second messenger cascade?
Phospholipase C
