Simulation Experiments for Neural Pulses - Brain Theory from a Circuits and Systems Perspective - page 183

Table A.1 Simulation
parameters

Rest potential 70 mV

Trigger voltage (both Na and K currents) 55 mV

Na current cutoff voltage +40 mV

K current cutoff voltage

90 mV

67.25 μA/cm 2

Sodium current

30.4 μA/cm 2 Potassium current

1 μF/cm 2

Membrane capacitance

0.3 mS/cm 2 Membrane conductance

Internal resistivity 15.7 Ω cm

ρ

Fig. A.1 Simplified hand
analysis of a neural pulse in
terms of Na and K currents

perfectly straight because of conductance effects that were ignored in the figure.
However, although an approximation, much can be learned from a simplified model.
Next the above parameters will to be scaled to the physical sizes of the regions
involved.

Physical Parameters

Short lengths of dendrite can be modeled as being tubular as in Fig. A.2 .
Segments could be any convenient size in a linear model, but here each segment
has a fixed diameter D 10 4 cm and length L 0.1 cm. The number of

segments n is left variable. Table A.2 summarizes equations for computing electri-
cal parameters from physical parameters. Table A.2 summarizes the results of a
calculation for the given segment.

1

¼ ¼