Olfactory pathway

The olfactory pathway handles smell.

Reception
The receptors lie in the nasal cavity, on the olfactory epithelium. Each receptor cell has several receptors, and lies in the olfactory mucosa. Chemicals in the air dissolve in the mucosa. If the chemical affects the receptor, it sends an action potential.

A special receptor system called the vomeronasal organ is connected to the nasal passage by a duct. It exlusively deals in pheromones.

Routes

 * The normal receptor cells project to the olfactory bulb, right above the nasal cavity.
 * The olfactory bulb projects to the pyriform cortex and the amygdala.
 * The pyriform cortex projects to the hypothalamus and the dorsomedial nucleus of the thalamus.
 * The receptors from the vomeronasal organ project to the accessory olfactory bulb.
 * This projects to the amygdala and hypothalamus.

Processing
Nobody really knows what all those regions do. Sad.

Project to

 * The thalamus projects to the orbitofrontal cortex (OFC). The OFC plays a central role in emotional and social behaviours, as well as eating.
 * The projection of the vomeronasal organ to the amygdala and hypothalamus plays a role in reproductive and social behaviour.