Morris-Lescar Model of Membranes with Multiple Ion Channels

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Application of various depolarizing currents to barnacle muscle fibers produces spikes or oscillations for some values of the applied current. The Morris–Lescar model, which is a simplified version of the Hodgkin–Huxley model, involves a fast-activating calcium current; a slow potassium current, which is coupled to the calcium current; and a passive leak. The nonlinear simultaneous differential equations display bifurcation corresponding to these modes of behavior for various values of the relevant parameters.

Contributed by: Benson R. Sundheim (May 2013)
Open content licensed under CC BY-NC-SA



An increase in the applied current first produces a steady state in the membrane voltage, then a transient spike, and finally continued oscillation. (Since the oscillations begin at nonzero frequencies, they are termed Type II.) Increasing the initial voltage causes a similar sequence of behavior (termed excitability), as does varying the relaxation rate. Each of these changes may be seen to be reflected as a bifurcation in the phase plane representation.

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