Plan of olfactory neuronsOlfactory 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.
Humans have between 10 and 20 million olfactory receptor neurons (ORNs).[3] In vertebrates, ORNs are bipolar neurons with 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]
Functionedit
ORs, which are located on the membranes of the cilia have been classified as a complex type of ligand-gated metabotropic channels.[7] There are approximately 1000 different genes that code for the ORs, making them the largest gene family. An odorant will dissolve into the mucus of the olfactory epithelium and then bind to an OR. ORs can bind to a variety of odor molecules, with varying affinities. The difference in affinities causes differences in activation patterns resulting in unique odorant profiles.[8][9] The activated OR in turn activates the intracellular G-protein, GOLF (GNAL), adenylate cyclase and production of cyclic AMP (cAMP) opens 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
Desensitizationedit
The olfactory receptor neuron has a fast working negative feedback response upon depolarization. When the neuron is depolarizing, the CNG ion channel is open allowing sodium and calcium to rush into the cell. The influx of calcium begins a cascade of events within the cell. Calcium first binds to calmodulin to form CaM. CaM will then bind to the CNG channel and close it, stopping the sodium and calcium influx.[10]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 odorsedit
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]
^Berkowicz, D. A.; Trombley, P. Q.; Shepherd, G. M. (1994). "Evidence for glutamate as the olfactory receptor cell neurotransmitter". Journal of Neurophysiology. 71 (6): 2557–61. doi:10.1152/jn.1994.71.6.2557. PMID 7931535.
^Vermeulen, A; Rospars, J. P. (1998). "Dendritic integration in olfactory sensory neurons: A steady-state analysis of how the neuron structure and neuron environment influence the coding of odor intensity". Journal of Computational Neuroscience. 5 (3): 243–66. doi:10.1023/A:1008826827728. PMID 9663551. S2CID 19598225.
^Saladin, Kenneth (2012). Anatomy & physiology : the unity of form and function (6th ed.). McGraw-Hill. p. 593. ISBN978-0073378251.
^Cunningham, A.M.; Manis, P.B.; Reed, R.R.; Ronnett, G.V. (1999). "Olfactory receptor neurons exist as distinct subclasses of immature and mature cells in primary culture". Neuroscience. 93 (4): 1301–12. doi:10.1016/s0306-4522(99)00193-1. PMID 10501454. S2CID 23634746.
^McClintock, TS; Khan, N; Xie, C; Martens, JR (5 December 2020). "Maturation of the Olfactory Sensory Neuron and Its Cilia". Chemical Senses. 45 (9): 805–822. doi:10.1093/chemse/bjaa070. PMC8133333. PMID 33075817.
^McEwen, D. P (2008). "Olfactory cilia: our direct neuronal connection to the external world". Curr. Top. Dev. Biol. Current Topics in Developmental Biology. 85: 333–370. doi:10.1016/S0070-2153(08)00812-0. ISBN9780123744531. PMID 19147011.
^Touhara, Kazushige (2009). "Insect Olfactory Receptor Complex Functions as a Ligand-gated Ionotropic Channel". Annals of the New York Academy of Sciences. 1170 (1): 177–80. Bibcode:2009NYASA1170..177T. doi:10.1111/j.1749-6632.2009.03935.x. PMID 19686133. S2CID 6336906.
^Bieri, S.; Monastyrskaia, K; Schilling, B (2004). "Olfactory Receptor Neuron Profiling using Sandalwood Odorants". Chemical Senses. 29 (6): 483–7. doi:10.1093/chemse/bjh050. PMID 15269120.
^Fan, Jinhong; Ngai, John (2001). "Onset of Odorant Receptor Gene Expression during Olfactory Sensory Neuron Regeneration". Developmental Biology. 229 (1): 119–27. doi:10.1006/dbio.2000.9972. PMID 11133158.
^Bradley, J; Reuter, D; Frings, S (2001). "Facilitation of calmodulinmediated odor adaptation by cAMP-gated channel subunits". Science. 294 (5549): 2176–2178. Bibcode:2001Sci...294.2176B. doi:10.1126/science.1063415. PMID 11739960. S2CID 13357941.
^Wei, J; Zhao, AZ; Chan, GC; Baker, LP; Impey, S; Beavo, JA; Storm, DR (1998). "Phosphorylation and inhibition of olfactory adenylyl cyclase by CaM kinase II in Neurons: a mechanism for attenuation of olfactory signals". Neuron. 21 (3): 495–504. doi:10.1016/s0896-6273(00)80561-9. PMID 9768837. S2CID 9860137.
^Yan, C; Zhao, AZ; Bentley, JK; Loughney, K; Ferguson, K; Beavo, JA (1995). "Molecular cloning and characterization of a calmodulin-dependent phosphodiesterase enriched in olfactory sensory neurons". Proc Natl Acad Sci USA. 92 (21): 9677–9681. Bibcode:1995PNAS...92.9677Y. doi:10.1073/pnas.92.21.9677. PMC40865. PMID 7568196.
^Bushdid, C.; Magnasco, M. O.; Vosshall, L. B.; Keller, A. (2014). "Humans Can Discriminate More than 1 Trillion Olfactory Stimuli". Science. 343 (6177): 1370–2. Bibcode:2014Sci...343.1370B. doi:10.1126/science.1249168. PMC4483192. PMID 24653035.
^Meister, Markus (2015). "On the dimensionality of odor space". eLife. 4: e07865. doi:10.7554/eLife.07865. PMC4491593. PMID 26151672.
^Gerkin, Richard C.; Castro, Jason B. (2015). "The number of olfactory stimuli that humans can discriminate is still unknown". eLife. 4: e08127. doi:10.7554/eLife.08127. PMC4491703. PMID 26151673.
^Magnasco, Marcelo O.; Keller, Andreas; Vosshall, Leslie B. (2015). "On the dimensionality of olfactory space". doi:10.1101/022103. {{cite journal}}: Cite journal requires |journal= (help)
External linksedit
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Insect olfaction
April 12, 2024
olfactory, receptor, neuron, olfactory, receptor, neuron, also, called, olfactory, sensory, neuron, sensory, neuron, within, olfactory, system, labels, german, zellen, cell, riech, smell, riechnerv, olfactory, nerve, cillien, cilia, detailssystemsmelllocationo. An olfactory receptor neuron ORN also called an olfactory sensory neuron OSN is a sensory neuron within the olfactory system 2 Olfactory receptor neuronLabels in German Zellen cell riech smell Riechnerv olfactory nerve cillien cilia DetailsSystemSmellLocationOlfactory epithelium in the noseShapeBipolar sensory receptorFunctionDetect traces of chemicals in inhaled air sense of smell NeurotransmitterGlutamate 1 Presynaptic connectionsNonePostsynaptic connectionsOlfactory bulbIdentifiersMeSHD018034NeuroLex IDnifext 116THH3 11 07 0 01003FMA67860Anatomical terms of neuroanatomy edit on Wikidata Plan of olfactory neuronsOlfactory 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 Contents 1 Structure 2 Function 2 1 Desensitization 2 2 Number of distinguishable odors 3 Other animals 4 See also 5 References 6 External linksStructure editHumans have between 10 and 20 million olfactory receptor neurons ORNs 3 In vertebrates ORNs are bipolar neurons with 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 editORs which are located on the membranes of the cilia have been classified as a complex type of ligand gated metabotropic channels 7 There are approximately 1000 different genes that code for the ORs making them the largest gene family An odorant will dissolve into the mucus of the olfactory epithelium and then bind to an OR ORs can bind to a variety of odor molecules with varying affinities The difference in affinities causes differences in activation patterns resulting in unique odorant profiles 8 9 The activated OR in turn activates the intracellular G protein GOLF GNAL adenylate cyclase and production of cyclic AMP cAMP opens 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 nbsp Desensitization of olfactory neuronDesensitization edit The olfactory receptor neuron has a fast working negative feedback response upon depolarization When the neuron is depolarizing the CNG ion channel is open allowing sodium and calcium to rush into the cell The influx of calcium begins a cascade of events within the cell Calcium first binds to calmodulin to form CaM CaM will then bind to the CNG channel and close it stopping the sodium and calcium influx 10 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 edit 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 editSee also Odor detection threshold Variation among species See also insect olfaction This section needs expansion You can help by adding to it February 2018 See also editChemoreceptor Sensory receptor List of distinct cell types in the adult human bodyReferences edit Berkowicz D A Trombley P Q Shepherd G M 1994 Evidence for glutamate as the olfactory receptor cell neurotransmitter Journal of Neurophysiology 71 6 2557 61 doi 10 1152 jn 1994 71 6 2557 PMID 7931535 Vermeulen A Rospars J P 1998 Dendritic integration in olfactory sensory neurons A steady state analysis of how the neuron structure and neuron environment influence the coding of odor intensity Journal of Computational Neuroscience 5 3 243 66 doi 10 1023 A 1008826827728 PMID 9663551 S2CID 19598225 Saladin Kenneth 2012 Anatomy amp physiology the unity of form and function 6th ed McGraw Hill p 593 ISBN 978 0073378251 Cunningham A M Manis P B Reed R R Ronnett G V 1999 Olfactory receptor neurons exist as distinct subclasses of immature and mature cells in primary culture Neuroscience 93 4 1301 12 doi 10 1016 s0306 4522 99 00193 1 PMID 10501454 S2CID 23634746 McClintock TS Khan N Xie C Martens JR 5 December 2020 Maturation of the Olfactory Sensory Neuron and Its Cilia Chemical Senses 45 9 805 822 doi 10 1093 chemse bjaa070 PMC 8133333 PMID 33075817 McEwen D P 2008 Olfactory cilia our direct neuronal connection to the external world Curr Top Dev Biol Current Topics in Developmental Biology 85 333 370 doi 10 1016 S0070 2153 08 00812 0 ISBN 9780123744531 PMID 19147011 Touhara Kazushige 2009 Insect Olfactory Receptor Complex Functions as a Ligand gated Ionotropic Channel Annals of the New York Academy of Sciences 1170 1 177 80 Bibcode 2009NYASA1170 177T doi 10 1111 j 1749 6632 2009 03935 x PMID 19686133 S2CID 6336906 Bieri S Monastyrskaia K Schilling B 2004 Olfactory Receptor Neuron Profiling using Sandalwood Odorants Chemical Senses 29 6 483 7 doi 10 1093 chemse bjh050 PMID 15269120 Fan Jinhong Ngai John 2001 Onset of Odorant Receptor Gene Expression during Olfactory Sensory Neuron Regeneration Developmental Biology 229 1 119 27 doi 10 1006 dbio 2000 9972 PMID 11133158 Bradley J Reuter D Frings S 2001 Facilitation of calmodulinmediated odor adaptation by cAMP gated channel subunits Science 294 5549 2176 2178 Bibcode 2001Sci 294 2176B doi 10 1126 science 1063415 PMID 11739960 S2CID 13357941 Wei J Zhao AZ Chan GC Baker LP Impey S Beavo JA Storm DR 1998 Phosphorylation and inhibition of olfactory adenylyl cyclase by CaM kinase II in Neurons a mechanism for attenuation of olfactory signals Neuron 21 3 495 504 doi 10 1016 s0896 6273 00 80561 9 PMID 9768837 S2CID 9860137 Yan C Zhao AZ Bentley JK Loughney K Ferguson K Beavo JA 1995 Molecular cloning and characterization of a calmodulin dependent phosphodiesterase enriched in olfactory sensory neurons Proc Natl Acad Sci USA 92 21 9677 9681 Bibcode 1995PNAS 92 9677Y doi 10 1073 pnas 92 21 9677 PMC 40865 PMID 7568196 Bushdid C Magnasco M O Vosshall L B Keller A 2014 Humans Can Discriminate More than 1 Trillion Olfactory Stimuli Science 343 6177 1370 2 Bibcode 2014Sci 343 1370B doi 10 1126 science 1249168 PMC 4483192 PMID 24653035 Meister Markus 2015 On the dimensionality of odor space eLife 4 e07865 doi 10 7554 eLife 07865 PMC 4491593 PMID 26151672 Gerkin Richard C Castro Jason B 2015 The number of olfactory stimuli that humans can discriminate is still unknown eLife 4 e08127 doi 10 7554 eLife 08127 PMC 4491703 PMID 26151673 Magnasco Marcelo O Keller Andreas Vosshall Leslie B 2015 On the dimensionality of olfactory space doi 10 1101 022103 a href Template Cite journal html title Template Cite journal cite journal a Cite journal requires journal help External links edit nbsp Wikimedia Commons has media related to Olfactory receptor neurons Insect olfaction Retrieved from https en wikipedia org w index php title Olfactory receptor neuron amp oldid 1214790398, wikipedia, wiki, book, books, library,
