a) Mapping of dendrites (Woolley et al., 1990) and axons (Shepherd et al., 2002) into a d = 1 dimensional transmission line with barriers of permeability k (Node 2.2.1.1 in Fig. 1). Here shows an example of caliber variation (blue) along an axon, and the local maxima (red) in caliber are identified as microstructural inhomogeneity along the axon. b) A system of randomly distributed disks in d = 2 dimensions (Node 2.2.1.2 in Fig. 1). c) A d = 3 dimensional system of random rods (Node 2.2.1.3 in Fig. 1). The panel a) is adapted with permission from (Woolley et al., 1990), Copyright 1990 Society for Neuroscience, and (Shepherd et al., 2002), Copyright 2002 National Academy of Sciences.