Figure 2.17

Membrane potential in a cable

(a) Steady state membrane potential as a function of distance in a semi-infinite cable in response to current injection at one end (x = 0 µm). The parameters are d = 1µm, Ra = 35.4 Ωcm, Rm = 10kΩcm2, which, from Equation 2.26, gives the length constant λ = 840 µm. (b) Top: a simulated excitatory postsynaptic current (EPSC). Below: the membrane potential measured at different points along a cable in response to the EPSC evoked at the left-hand end of the cable. The colour of each trace corresponds to the locations of the electrodes. The neurite is 500 µm long and other parameters are the same as the semi-infinite cable shown in (a).

Simulation environment:
NEURON How do I run a simulation using NEURON?
Notes

There are separate simulation files for (a) and (b). To run either simulation:

  1. In the RunControl window click on Init & Run.
  2. The time course of the membrane potential at various locations along the axon appears in the Graph[0] window.
  3. The membrane potential as a function of distance along the axon in appears in the Graph[1] window.

To observe how the spatial distribution of the membrane potential varies over time:

  1. In the RunControl window click on Init (mV).
  2. In the RunControl window click on Continue for (ms) repeatedly.
Download:
Binary Data fig-2-17a.nrnzip, Binary Data fig-2-17b.nrnzip