Modelled temperature-dependent excitability behaviour of a generalised human peripheral sensory nerve fibre

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 microm. 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 microm. Calculated strength-duration time constants ranged from 128.5 to 183.0 micros at 37 degrees 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.

Threshold predictions of different pulse shapes using a human auditory nerve fibre model containing persistent sodium and slow potassium currents

“…As discussed in the Methods section, the axonal part of the ANF model used in the present study is based on the general peripheral sensory nerve fibre model developed in Smit et al (2009b,c). In Smit et al (2009b) evidence was provided that the general sensory nerve fibre model is not in full accord with the McNeal (1976) results when nodal strangulation is included in the model, since for larger diameter fibres (larger than 10.0 mm) a decrease in threshold current occurred with an increase in diameter. However, when nodal strangulation was excluded from the model, the general nerve fibre model did comply fully with the McNeal (1976) results.…”

“…The original HH model, and hence the Rattay et al (2001) model, contains an I Nat current, although it activates and inactivates at slower rates than the I Nat current of the human ANF model (refer to Smit et al, 2009c). Two versions of the human ANF model were developed: one including a 100% I Nat and the one used in the present study that included both a 2.5% I Nap and 97.5% I Nat (Smit et al, 2008(Smit et al, , 2009b. Fig.…”

“…Although the soma employs the HodgkineHuxley dynamics as described by Rattay et al (2001), its diameter is smaller than in the Rattay model. The axonal section employs the human sensory nerve fibre dynamics and morphometry and morphology described in Smit et al (2009b). Unlike in the Rattay model, internodal lengths are considered constant and are shorter than in the Rattay model.…”

“…The human Type I ANF model is based on the cable model by Rattay et al (2001), but with the axon replaced by the generalised human sensory nerve fibre model described in Smit et al (2009b). The ANF model consists of a dendrite, soma and axon (Fig.…”

A 3D Computational Model of Transcutaneous Electrical Nerve Stimulation for Estimating Aβ Tactile Nerve Fiber Excitability

“…Although sensory nerve model had been studied for many years (Schwarz et al, 1995; Wesselink et al, 1999; Smit et al, 2009; Howells et al, 2012), the specific active model of tactile sensory fibers had not been studied in detail during the TENS. Our tactile nerve fiber model adopted the widely-accepted double-cable-layer model structure.…”