2007 Sensory Physiology

• the olfactory epithelium is located at the top of the nasal cavity
• unlike the receptors of the other special senses, the olfactory receptor membrane is found on the primary afferent neurons (i.e., receptor=primary afferent)
• olfactory receptor cells are the only neurons that are regularly replaced throughout life (via development of basal cells)
• axons of olfactory receptor neurons (ORNs) enter the CNS through the cribriform plate to synapse in the olfactory bulb
• odourants are dissolved in the mucus layer and are bound to olfactory binding proteins

(Relatively) New discoveries

• mammals have 2 types of olfactory epithelia:  MAIN OLFACTORY EPITHELIUM (MOE) and VOMERONASAL ORGAN (VNO)

• and 3 types of receptor neuron:

  • in MOE:  OLFACTORY RECEPTOR NEURONS (ORNs) and GC-D NEURONS

  • in VNO:  VOMERONASAL NEURONS
• different types of olfactory receptor neuron utilize different transduction proteins and central pathways

Zufall and Monger 2001