Modelled temperature-dependent excitability behaviour of a generalised human peripheral sensory nerve fibre |
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Authors: | Jacoba E Smit Tania Hanekom Johan J Hanekom |
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Institution: | (1) Department of Electrical, Electronic and Computer Engineering, University of Pretoria, Lynnwood Road, Pretoria, 0002, South Africa;(2) Present address: Biophotonics Group, CSIR National Laser Centre (NLC), Building 46, P.O. Box 395, Pretoria, 0001, South Africa |
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Abstract: | The objective of this study was to determine if a recently developed human Ranvier node model, which is based on a modified
version of the Hodgkin–Huxley model, could predict the excitability behaviour in human peripheral sensory nerve fibres with
diameters ranging from 5.0 to 15.0 μm. The Ranvier node model was extended to include a persistent sodium current and was
incorporated into a generalised single cable nerve fibre model. Parameter temperature dependence was included. All calculations
were performed in Matlab. Sensory nerve fibre excitability behaviour characteristics predicted by the new nerve fibre model
at different temperatures and fibre diameters compared well with measured data. Absolute refractory periods deviated from
measured data, while relative refractory periods were similar to measured data. Conduction velocities showed both fibre diameter
and temperature dependence and were underestimated in fibres thinner than 12.5 μm. Calculated strength–duration time constants
ranged from 128.5 to 183.0 μs at 37°C over the studied nerve fibre diameter range, with chronaxie times about 30% shorter
than strength–duration time constants. Chronaxie times exhibited temperature dependence, with values overestimated by a factor
5 at temperatures lower than body temperature. Possible explanations include the deviated absolute refractory period trend
and inclusion of a nodal strangulation relationship.
At the time of this research J. E. Smit was with the University of Pretoria. |
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Keywords: | Computational nerve fibre model Conduction velocity Chronaxie Refractory periods Persistent sodium current |
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