ABSTRACT
The method of mathematical modeling and computational simulations of human motor nerve fi bres in normal and abnormal cases are generally used to reveal some of the mechanisms underlying nerve excitability abnormalities observed and recorded in patients with demyelinating neuropathies and neuronopathies. The simulations presented here apply our model (Stephanova 2001), in which 150 interconnected parallel lamellae are simulated by alternating 150 lipid and 150 aqueous layers within the myelin sheath. The aqueous layers provide appreciable longitudinal and radial conductance, the latter via a spiral pathway (Fig. 1). This multi-layered model of the human motor nerve fi bre is a further development of the double cable models (Blight 1985, Halter and Clark 1991, Stephanova and Bostock 1995, 1996). It is derived from the model of Stephanova and Bostock (1995) in which the myelin sheath and internodal axolemma are treated as two concentric cables (Fig. 2). All calculations are carried out for fi bres with: an axon diameter of 12.5 µm; an external fi bre diameter of 17.3 µm; nodal diameter of 5 µm; nodal area of 24 μm2; myelin thickness of 2.4 μm; periodicity of myelin lamellae of 16 nm and periaxonal space thickness of 20 nm. The temperature is 37ºC.
