These are cells in the olfactory epithelium that detect chemicals in the air called odorants using specialized receptors. These neurons can be replaced in adults (Costanzo, 1991). 

The olfactory receptor neurons consist of multiple structures that assist in detecting odorants. 

- cilia
- dendritic knob

Olfactory receptor neurons

This is the layer of cells that lines the nasal cavity.

Olfactory epithelium 

The olfactory receptor neurons are the major component in the olfactory sensory system. The olfactory receptor neuron is a bipolar neuron, the cell body is embedded in the nasal chamber and within the olfactory epithelium. Its nonmyelinated axon transduces the signal to the olfactory bulb without discontinuity.

In the nose, there are three types of cells in the olfactory epithelium. 

- Olfactory receptor neurons
- Basal cells 
- Supporting cells 

Ohio State University, Columbus

Chemicals in the air trigger odor sensation

- receptors in the nose
- transmission to brain regions
- anosmia

Smell

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

Receptors in the nose 

Olfactory transmission to the brain involves many parts that are necessary to understanding how smell is perceived. 

- odorants
- olfactory bulb
- glomerulus
- mitral cells
- prepyriform cortex 
- orbitofrontal cortex
- amygdala 

It should be noted that olfaction is the only sensory process that does not pass through the thalamus before synapsing in the cortex. 



Olfactory transmission to brain regions

This is a condition in which a person lacks the ability to smell. It is also sometimes referred to as odor blindness. 

Anosmia

This is a highly specialized system that detects pheromones and sends the information to the brain. This system is found in most terrestrial mammals. 

Vomeronasal system

Olfactory training is a non-pharmacological and non-surgical treatment for patients with olfactory dysfunction. UPSIT (University of Pennsylvania Smell Identification Test) is the most common olfactory training in North America. UPSIT is based on microencapsulated odorants released from the surface of strips. Each subject tags 40 odorants on a multiple-choice list.

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