Figure 6
Dendritic morphology and morphoelectrotonic transforms of a cervical motoneuron. Morphology (A) and METs (B) and (C) of the same MN (C-167) with homogeneous (Rms = Rmd) and inhomogeneous (Rms < Rmd) soma-dendrite membranes constrained by the physiological 5 MΩ somatic input resistance of the MN for both METs. Arrows 1 and 2 point to homologous proximal (red) and distal (green) dendritic branches where changes during METs are visibly non-proportional to their geometrical sizes (for quantitative analysis see body text). Arrows labeled by S point to the center of the soma (its entire shape is not shown in the figures). D-dorsal, V-ventral, M-medial, L-lateral directions. Note the different size of the MET with our choice of the physiologically constrained pair of Rms-Rmd values in the inhomogeneous soma-dendritic membrane (C) relative to the MET of the same MN with homogeneous membrane (B) drawn to a common scale of space constants. Both METs show attenuations of somatopetal PSP propagation (‘Vin mode’ in NEURON) at DC input (frequency = 0 Hz), recording electrode was at mid-soma, stimulating electrode was at mid-points of dendritic compartments. Dendritic and somatic specific membrane resistances (Rmd and Rms) were equally 8348 Ωcm2 for the homogeneous soma-dendritic membrane, while for the MET with inhomogeneous membrane Rmd and Rms were 20000 and 1046 Ωcm2 respectively. With these Rms and Rmd values the somatic input resistance was 5 MΩ in both membrane models of the MN.