Biomedical subjects

E Skaugen

Publications and source records attributed to E Skaugen.

3 recordsLinked to original sources

PubMed1980

Firing behaviour in stochastic nerve membrane models with different pore densities.

A stochastic nerve membrane model with a two-state pore system was investigated by computer simulation in the uniform (space-clamped) case. The model was based upon the Hodgkin-Huxley equations for the giant axon in squid, but where both the maximal membrane conductances and the rate constants were changed systematically. This was done in order to simulate nerve membranes of small axons, where both of these parameters are smaller than in squid. It was found that the effects upon the firing behaviour due to a finite number of pores were not greatly affected by changes in these parameters. When the specific injected current was calculated relative to the maximal membrane conductances, the threshold for firing was increased somewhat, and the frequency-current relationship became slightly more linear when the maximal conductances (or pore density) were decreased, or the rate constants increased. In the discussion it is shown how the results obtained could be applied qualitatively to the firing behaviour of nerve cells, and that firing in small nerve cells should be significantly influenced by the stochastic effects of a finite number of pores. Gating currents were also discussed, and their effects were found to be insignificant in small nerve cells.

Action Potentials↗

PubMed1980

Firing behaviour in nerve cell models with a two-state pore system.

The firing behaviour of simple nerve cell models with a two-state pore system was investigated by computer simulation. The pores were assumed to open and close randomly, with the probabilities for opening an closing calculated from the equations found by Hodgkin and Huxley for the squid giant axon. The cell models had a cell body and an axon with an initial segment with a smaller diameter. Both the case of a uniform membrane with constant pore densities all over the cell, and the case of a cell body membrane with only a leakage conductance (a "passive" membrane) were investigated. The results indicate that the firing behaviour of a small nerve cell may be significantly influenced by the finite number of pores in the initial segment. In contrast to the original Hodgkin-Huxley equations which give a very non-linear frequency-current relationship in such nerve cell models, a fairly linear relationship over a large current range was found in many cases. It was estimated that the diameter of the initial segment must be less than approximately 1 micron and the length larger than half a space constant, in order to obtain a current frequency relationship significantly different from that predicted by the original Hodgkin-Huxley equations.

Mathematics↗

PubMed1979

Firing behaviour in a stochastic nerve membrane model based upon the Hodgkin-Huxley equations.

A nerve membrane model with a two-state pore system was investigated by computer simulation in the uniform (space-clamped) case. Both sodium and potassium conducting pores were modelled, each pore having four independent gates which switched randomly between the open and the closed position, governed by the assumed rate constants. Each pore conducted only when all the gates were open. The model was based upon the Hodgkin-Huxley equations for the giant axon in squid, and in the limit of an infinite number of pores it was identical to these. The firing behaviour of this model as a function of the number of pores and the injected current were investigated. The mean firing frequency and the distribution of interspike intervals were mainly used in the presentation of the results. It was found that for pore numbers less than about 20 000 the main effects due to a finite number of pores were a lowering of the current threshold for firing and a more linear frequency current relationship relative to that of the original H-H equations. For higher pore numbers an increase in the current threshold and a pronounced burst firing close to the threshold were found.

Animals↗