Olfactory receptor neuron

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Olfactory receptor neuron
Glutamate[1]
Presynaptic connectionsNone
Postsynaptic connectionsOlfactory bulb
Identifiers
MeSHD018034
NeuroLex IDnifext_116
THH3.11.07.0.01003
FMA67860
Anatomical terms of neuroanatomy]
Plan of olfactory neurons
Olfactory sensory neurons (OSNs) express odorant receptors. The axons of OSNs expressing the same odorant receptors converge onto the same glomerulus at the olfactory bulb, allowing for the organization of olfactory information.

An olfactory receptor neuron (ORN), also called an olfactory sensory neuron (OSN), is a sensory neuron within the olfactory system.[2]

Structure

Humans have between 10 and 20 million olfactory receptor neurons (ORNs).

dendrites facing the external surface of the cribriform plate with axons that pass through the cribriform foramina with terminal end at olfactory bulbs. The ORNs are located in the olfactory epithelium in the nasal cavity. The cell bodies of the ORNs are distributed among all three of the stratified layers of the olfactory epithelium.[4]

Many tiny hair-like non-motile

cilia protrude from the olfactory receptor cell's dendrites. The dendrites extend to the olfactory epithelial surface and each ends in a dendritic knob from which around 20 to 35 cilia protrude. The cilia have a length of up to 100 micrometres and with the cilia from other dendrites form a meshwork in the olfactory mucus.[5] The surface of the cilia is covered with olfactory receptors, a type of G protein-coupled receptor. Each olfactory receptor cell expresses only one type of olfactory receptor (OR), but many separate olfactory receptor cells express ORs which bind the same set of odors. The axons of olfactory receptor cells which express the same OR converge to form glomeruli in the olfactory bulb.[6]

Function

ORs, which are located on the membranes of the cilia have been classified as a complex type of

ion channels in the cell membrane, resulting in an influx of sodium and calcium ions into the cell, and an efflux of chloride ions. This influx of positive ions and efflux of negative ions causes the neuron to depolarize, generating an action potential
.

Desensitization of olfactory neuron

Desensitization

The olfactory receptor neuron has a fast working negative feedback response upon

CaMKII will be activated by the presence of CaM, which will phosphorylate ACIII and reduce cAMP production.[11] CaMKII will also activate phosphodiesterase, which will then hydrolyze cAMP.[12]
The effect of this negative feedback response inhibits the neuron from further activation when another odor molecule is introduced.

Number of distinguishable odors

A widely publicized study suggested that humans can detect more than one trillion different odors.[13] This finding has been disputed. Critics argued that the methodology used for the estimation was fundamentally flawed, showing that applying the same argument for better-understood sensory modalities, such as vision or audition, leads to wrong conclusions.[14] Other researchers have also showed that the result is extremely sensitive to the precise details of the calculation, with small variations changing the result over dozens of orders of magnitude, possibly going as low as a few thousand.[15] The authors of the original study have argued that their estimate holds as long as it is assumed that odor space is sufficiently high-dimensional.[16]

Other animals

See also: Odor detection threshold § Variation among species
See also: insect olfaction

See also

References

  1. PMID 7931535
    .
  2. S2CID 19598225
    .
  3. ISBN 978-0073378251
    .
  4. S2CID 23634746
    .
  5. PMID 33075817
    .
  6. PMID 19147011
    .
  7. S2CID 6336906
    .
  8. PMID 15269120
    .
  9. PMID 11133158
    .
  10. S2CID 13357941
    .
  11. S2CID 9860137
    .
  12. PMID 7568196
    .
  13. PMID 24653035
    .
  14. PMID 26151672
    .
  15. PMID 26151673
    .
  16. doi:10.1101/022103. {{cite journal}}: Cite journal requires |journal= (help
    )

External links

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