Download Receptors of the Olfactory System

Faizan Kalwar
Basal cells – replace receptor neurons (a feature unique
to the olfactory neurons)
Sustenacular cells – scattered throughout epithelium,
secretory granules empty contents on mucosal surface
Receptor neurons
- Humans have ~40 million
- Bipolar neurons
- Dendrites extend into
mucosal surface
-Cilia on surface of dendritic
knobs
-Receptors on cilia make
contact with odorants
-One receptor for each neuron
- Axons lead into glomerus
-Odor molecule binds to receptor
protein on surface of cilia
-Receptor conformation changes 
activates G-protein (Golf)
-Adenylate cyclase activation
produces cAMP
-cAMP opens ion channels  Na+
and Ca2+ enter
- Depolarization occurs at dendritic
region which leads to generation
of an action potential
-Activation of multiple receptors allows molecules that
have never been encountered to be characterized
-ORNs are sensitive to a subset of odorants which
makeup its tuning curve
- Some ORNs are very selective while others are much
broader
-Different thresholds exist for a given odorant between
neurons with the same receptor
- Adaptations occur