Persistent Link:
http://hdl.handle.net/10150/282741
Title:
Mathematical models of ionic diffusion in olfactory glomeruli
Author:
Rado, Anita, 1967-
Issue Date:
1998
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Many vertebrate and invertebrate olfactory systems are similar in the organization of their synaptic neuropil into glomeruli, structures surrounded by an incomplete layer of glial processes. Within glomeruli, the axons of olfactory receptor neurons synapse with the dendrites of their target brain neurons. Glomeruli are likely to be odor specific in that each glomerulus processes information from a subset of axons about a particular chemical feature of odorant molecules. Therefore, a large proportion of the neurons within a glomerulus may be excited simultaneously in response to a particular odor. The resulting release of potassium ions from neurons may be sufficient to cause a substantial increase in the extracellular concentration of potassium ions and thus affect the excitability of neighboring neurons. The goal of this study is to develop theoretical models for the diffusion of potassium ions in the extracellular space, and to predict how the glial border affects the spread of potassium ions following the activation of olfactory sensory neurons. Observations of the morphology of the interior and border of the glomerulus were used to estimate the porosity and effective diffusivity of these regions, and the size of the "mouth" region where there is no glial covering. Potassium was assumed to be released into the extracellular space during an initial 0.5 seconds. The time-dependent diffusion equation was solved in spherical coordinates using a finite-difference method. The results indicated that the glial envelope forms a partial barrier to the diffusion of potassium ions, and greatly reduces the spread of potassium ions to neighboring glomeruli following release. According to the model, the decline in potassium concentration within the glomerulus due to the leakage from the mouth and glial boundaries is relatively slow, taking more than 10 seconds to approach its resting level. These findings support the hypothesis that the characteristic distribution of glial cells around glomeruli could play a significant role in olfactory information processing.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Mathematics.; Biophysics, General.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Applied Mathematics
Degree Grantor:
University of Arizona
Advisor:
Secomb, Timothy; Tolbert, Leslie; Tabor, Michael

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleMathematical models of ionic diffusion in olfactory glomerulien_US
dc.creatorRado, Anita, 1967-en_US
dc.contributor.authorRado, Anita, 1967-en_US
dc.date.issued1998en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractMany vertebrate and invertebrate olfactory systems are similar in the organization of their synaptic neuropil into glomeruli, structures surrounded by an incomplete layer of glial processes. Within glomeruli, the axons of olfactory receptor neurons synapse with the dendrites of their target brain neurons. Glomeruli are likely to be odor specific in that each glomerulus processes information from a subset of axons about a particular chemical feature of odorant molecules. Therefore, a large proportion of the neurons within a glomerulus may be excited simultaneously in response to a particular odor. The resulting release of potassium ions from neurons may be sufficient to cause a substantial increase in the extracellular concentration of potassium ions and thus affect the excitability of neighboring neurons. The goal of this study is to develop theoretical models for the diffusion of potassium ions in the extracellular space, and to predict how the glial border affects the spread of potassium ions following the activation of olfactory sensory neurons. Observations of the morphology of the interior and border of the glomerulus were used to estimate the porosity and effective diffusivity of these regions, and the size of the "mouth" region where there is no glial covering. Potassium was assumed to be released into the extracellular space during an initial 0.5 seconds. The time-dependent diffusion equation was solved in spherical coordinates using a finite-difference method. The results indicated that the glial envelope forms a partial barrier to the diffusion of potassium ions, and greatly reduces the spread of potassium ions to neighboring glomeruli following release. According to the model, the decline in potassium concentration within the glomerulus due to the leakage from the mouth and glial boundaries is relatively slow, taking more than 10 seconds to approach its resting level. These findings support the hypothesis that the characteristic distribution of glial cells around glomeruli could play a significant role in olfactory information processing.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectMathematics.en_US
dc.subjectBiophysics, General.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineApplied Mathematicsen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorSecomb, Timothyen_US
dc.contributor.advisorTolbert, Leslieen_US
dc.contributor.advisorTabor, Michaelen_US
dc.identifier.proquest9901772en_US
dc.identifier.bibrecord.b38838254en_US
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