SmellOlfactory EpitheliumWhat would happen if we ablated (eliminated) all basal cells?Slide 4SmellSlide 6Slide 7SmellSlide 9Slide 10Slide 11Slide 12Why is it important to have lateral inhibition?Adult NeurogenesisSlide 15SummarySmell•How do we detect odorants?•How do we code for odorants?•Where does smell information go once we’ve detected it?Olfactory EpitheliumOlfactory BulbOlfactory EpitheliumOlfactory NerveBasal CellOlfactory Receptor CellCiliaMucus layerWhat would happen if we ablated (eliminated) all basal cells?a) The sense of smell would instantly be lost.b) The sense of smell would slowly be lost.c) The sense of smell would not be affected.d) The sense of smell would be enhanced instantly.e) The sense of smell would be enhanced slowlySmell•How do we detect odorants?•How do we code for odorants?•Where does smell information go once we’ve detected it?Olfactory neural codingAre odorants coded using population coding or labeled line coding?a) Population codingb) Labeled line codingSmell•How do we detect odorants?•How do we code for odorants?•Where does smell information go once we’ve detected it?Olfactory pathwayMap of Olfactory BulbLateral Inhibition between neighboring glomeruliWhy is it important to have lateral inhibition?a) So that only one glomerulus is active at a time.b) To enhance contrast between similar odors.c) Population coding requires that lots of neurons are active.Adult NeurogenesisOlfactory pathwaySummary•Olfactory receptor cells detect odorants using G-protein-coupled receptors, with each cell expressing just a single receptor type•When an odorant activates a receptor, all the receptors use a common mechanism to depolarize the olfactory receptor cell–G-protein activates adenylyl cyclase–Adenylyl cyclase converts ATP to cAMP–cAMP opens cation channels, depolarizing the membrane–Calcium flowing through the cation channels opens chloride channels, which also depolarize the membrane (due to high internal chloride concentration)–An action potential is generated and causes the release of neurotransmitter•Olfactory receptor cells expressing the same receptor project to a single glomerulus in the olfactory bulb•Glomeruli are organized in a “map”- similar odorants activate adjacent regions- and lateral inhibition between neighboring glomeruli helps the brain distinguish between similar odorants•To consciously detect smell, the information goes from the olfactory bulb to the olfactory tubercle to the thalamus to the orbitofrontal cortex, although there are direct connections from the olfactory bulb to limbic (emotion)