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SMELL (Central Olfactory Pathways (Mapping (Glomeruli receive input only…
SMELL
Central Olfactory Pathways
Olfactory axons converge at glomeruli
Terminate at dendrite of 2nd order neurons
Axons travel through olfactory tracts to olfactory cortex
BYPASS THE THALAMUS
Mapping
Glomeruli receive input only from specific receptors
Cells expressing a given gene go to only 2 glomeruli in each bulb
Primary Olfactory Cortex (piriform cortex)
Mitral cells to project to anterior and posterior piriform cortex
Info sent to temporal lobe structures
emotion, motivation, memory
SKIPS THALAMUS
Orbifrontal Neocortex
Mitral project to olfactory tubercle and MD thalamus
Info to orbifrontal neocortex
conscious perceptions of smell, odor discrimination
Spatial and Temporal Representations of Olfactory Information
Population Coding
#
Spatial Maps
Inputs from one olfactory receptor diverges to many areas of olfactory cortex
Timing of Action Potentials
Cortical neurons integrate signals
convergence
to recognize ONE odor --> need to be synchronously activated
Can respond to mixture; but not that single odorant
Inputs from receptors are segregated in olfactory bulb and epithelium
Organs of the Olfactory
olfactory epithelium
olfactory receptor cells
receptors on cilia that extend into mucus
odorants bind to receptor proteins
Stimulate G-protein (G olf)
αOLF
Adenylyl cyclase activated
Form cAMP that opens a cAMP gated cation channels
Influx of Na+ and Ca2+
Open Ca2+ activated Cl- channels
Cl- efflux --> depolarization
goes out bc of high concentration intercellularly
receptors
About 350
Three different gene families
each receptor cell receives input from only one G-protein coupled receptor (GPCR)
Broadly tuned but have preferences odors over others
population coding
supporting cells
basal cells
