Table 3.

Model parameters to estimate the bulk transverse endoneurial resistivity for a bundle of unmyelinated axons.

Parameter (variable name)	Default value	Test range	References
Fascicle diameter (dfasc)	105 μm	80–300 μm	(Kawagishi, 2008; Tweden, 2013)
Axon diameter (daxon)	1 μm	0.5–2 μm	(Giordano, 2005; Guo, 1987; Helmers, 2012; Mei et al., 1980; Robinson, 1972; Waataja, 2011)
Axonal area fraction (AAF)a	0.435b	0.20–0.737c	(Agostini, 1957; Altman and Plonsey, 1989)
Endoneurial resistivity (ρendo-micro)	0.65 Ω-m	0.5–2 Q-m	(Altman and Plonsey, 1989; Geddes and Baker, 1967b)
Intracellular resistivity (ρa)	0.7 Ω-m	0.5–4 Q-m	(McIntyre et al., 2002; McIntyre and Grill, 2000)
Specific membrane resistance (Rm)	0.2 Ω-m2	0.0025–0.4 Ω-m2 d	(Barrett and Crill, 1974; Cole and Hodgkin, 1939)

^aTable 5 (Supplement C) shows calculations for estimating the axonal area fraction for a single fascicle based on cat posterior abdominal vagus nerve morphology.

^bAlthough we estimated an axonal area fraction of 0.45 from cat posterior abdominal vagus nerve histology slides (Table 5, Supplement C), we could only achieve AAF = 0.435 in the finite element model with the default parameters.

^cThe lower bound of this range was chosen arbitrarily simply to test model sensitivity to this parameter. The upper bound is the maximum extent to which we could pack 2 μm axons into a 105 μm diameter fascicle.

^dThe lower bound of this range represents the minimum membrane resistance for squid giant axon if all axons in the fascicle are active simultaneously.