olfactory receptor
Acronym:
OLR
The term olfactory receptor (OLR) refers to a neuron with an oderant-sensitive apical dendrite embedded in the olfactory epithelium that lines the nasal cavity. There are two types. The more numerous main olfactory receptors (OLRm} have dendritic fibers in the epithelium that underlies the cribriform plate, the roof of the nasal cavity. Their cell bodies lie in the cranial cavity above the cribriform plate and project via the terminal nerve (tn) to the main olfactory bulb (MOB). OLRm's are found in the human ( Buck-2013 ), macaque ( Price-1990 ) and rodents ( Wirsig-Wiechmann-2001 ).
Less numerous are the accessory olfactory receptors (OLRa) whose cell bodies are located in the vomeronasal organ (VNO). The VNO is embedded in the epithelium of the nasal septum rostral and ventral to the OLRm's ( Barral-2009 ). Their axons project in the vomeronasal nerve (vn) component of the vomeronasal-terminal nerve complex (vtnc) through the cribriform plate to the accessory olfactory bulb (AOB) ( Barral-2009 Wirsig-Wiechmann-2001 ). The VNO and AOB are. quite prominent in the rodent ( Wirsig-Wiechmann-2001 ) but less so in the human and may be absent in the macaque ( Zhang-2003 Francia-2014 ).
OLRm's respond to most oderant molecules; OLRa's respond exclusively to pheromones, oderant molecules that signal the presence of another individual. The VNO not only projects to the AOB but has a reciprocal connection from the AOB that runs in the same terminal nerve. That input releases gonadotrophin-releasing hormone (GnRH). GnRH in other parts of the brain has distinctly different effects in males and females .( Wirsig-Wiechmann-2001 ). The presence of information as to the sexual category of both the stimulus individual and the preceirver suggests that the unique sensorimotor pathway from oderant stimulus to the appropriate behavioral response begins at the very first level of the olfactory system.
In the human, the total number of olfactory receptor neurons on the two sides of the nose is ~10,000,000 ( Wikipedia ).The number of variants of protein receptor molecules is approximately150 ( Purves-2001 ). The maximal number of possible combinations and permutations of 150 variants (150-squared) is 22,500... more than enough to account for the human ability to detect ~5,000 to10,000 distinct oderants ( Purves-2001 Buck-2013 ).
In animals, pheromonest play an essential role in territorial marking, sexual attraction and other aspects of reproductive function. In humans they are involved in the synchronization of menstrual cycles of women living in close residential contact, such as a convent or boarding school ( Barral-2009 ). Updated 29 Jun 2024.
Also known as: No other name for this structure has appeared in PubMed.NeuroNames ID : 5714
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