This is where the specialized receptor cells are located that detect pheromones. It is located near the olfactory epithelium, but is separate. 

Vomeronasal organ (VNO)

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

Ohio State University, Columbus

Chemicals in the air trigger odor sensation

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

Smell

Pheromones are specialized chemical messages secreted by an individual to communicate with other members of the same species. This type of communication is often utilized to broadcast a potential mate's reproductive status.

Pheromones

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

Behavioral Neuroscience 8th Edition

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

- Olfactory receptor neurons
- Basal cells 
- Supporting cells 

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

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.

Olfactory training

It has been observed in male rodents that the vomeronasal organ, which contains receptor sensory cells, detects pheromones from females. This sends axons to the olfactory bulb in the brain. These neurons launch to the medial amygdala, which circulates testosterone to maintain a masculine function during copulation. This sends axons to the mPOA, which merges all of this information to lead to ejaculation. 

Male Copulatory Circuitry in Rodents

One specific instance where pheromones are seen to communicate between individuals of the same sex is in elephants. During the elephant's mating season, males emit a liquid pheromone behind their eyes that has a distinctive smell. This certain pheromone displays a lower rank, which helps them avoid superior "mature-smelling" males, and therefore avoid fights. 

Communication between individuals of the same sex

These are receptors produced in the olfactory epithelium, and are possible pheromone receptors.

Trace amine-associated receptors (TAARs) 

Pheromones Reference Library

Pheromones are not a regular hormone, they are considered ectohormones because they are secreted outside of the body and they influence another individual's behavior. 

Ectohormone

1. Releaser
2. Primer
3. Signaler
4. Modulator

Types of Pheromones

In certain species like rats, pheromonal signals play a critical role in mating behaviors. For instance, a female rat prepared to reproduce will release pheromones to draw the attention of nearby males. This pheromonal activation is an important factor in triggering sexual behavior in the male rat.

Pheromonal Communication in Rats

While pheromonal communication is well-documented in many animals, the role and existence of pheromones in humans remain a subject of significant scientific research and ongoing controversy.

Research and Controversy on Human Pheromones

Analyze the following scenario and identify the specific type of chemical communication being used. Justify your answer by explaining how the elements of the scenario fit the definition of this communication type.

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