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Professor Jian Yang...

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olfactory epithelium: lines ~1/2 of interior of nose o axons from olfactory receptor neurons found here project directly to neurons in the olfactory bulb (across gap - cribriform plate) unique among sensory systems bc d/n include a thalamic relay from primary receptors to a cortical region that processes the sensory information o olfactory sensory info is processed in the pyriform cortex why difference between animals and humans in olfactory perception? o increased # of olfactory receptor neurons and odorant receptor proteins in an expanded olfactory epithelium o larger portion of forebrain devoted to olfaction nasal mucosa consists of: o olfactory receptor neurons (ORNs)  has single dendritic process that turns into knoblike protrusion from which olfactory cilia extend into a thick layer of mucus  direct access to odorant molecules, but also exceptionall exposed to airborne pollutants/harmful substances o bowman's gland - produce mucus that protects exposed receptor neurons/supporting cells of olfactory epithelium o basal cells o supporting cells neural regeneration is a gradual process o most olfactory neurons in rodents are renewed every 6-8 weeks odor transduction o compartmental sensitivity of cilia to odors: odorants evoke a large inward (depolarizing) current when applied to the cilia, but only a small current when applied to the cell body

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odorant receptor gene family olfactory receptor are GPCRs specificity of odorant recognition/signal transduction is the result of this molecular variety of odorant receptor proteins in the nasal epithelium  largest known single gene family, representing 3-5% of the genome IN ALL MAMMALS  

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pseudogene - sequence of DNA that cannot be transcribed into a stable mRNA or transcript cannot be translated into a protein o mammalian odorant receptor genes d/n have introns, but invertebrates do mechanism of odor transduction o odorant binds to odor receptor protein -> Golf alpha subunit dissociates -> activates adenyl cyclase III (ACIII) -> increases cAMP -> activates cyclic nucleotide-gated channels (nonselective cation channels - Na+, K+, Ca2+) -> permits entry of Na+ and Ca2+ (mostly Ca2+) -> depolarizes neuron how to turn off response Ther ec ept orpot ent i al i sr educ edi nmagni t udewhenc AMPi sbr ok endownbys pec i fi c o 2+c phos phodi es t er as est or educeI t sc onc ent r at i on.At t hes amet i me,c ompl e x eswi t hc al modul i n a t saffi f o r c AMP . ( ( a1t CAM)andbi ndst ot hec hannel ,r educ i ngi n i t y Fi nal l y ,Cal +I se xt r udedt hr ought he ( a2+f Na+ex c hangepat hway ....