Biol 595N: Intro to Neuroscience

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Biol 595N Intro to Neuroscience
Morris-Lecar Model
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Voltage Oscillations in the Barnacle Giant Muscle
Fiber
Catherine Morris and Harold Lecar Biophysical
Journal 35 (1981) 193-213
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Biophysical Journal 35(1981) 193-213
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Experiments done in fibers excised from the
depressor scutorum rostralis muscles of the
Balanus nubilus. Previous work done by many
researchers had suggested this muscle is a
relatively simple system that uses voltage
dependent Ca2 and K channels that do not
inactivate under current stimulation. Also
evidence for Ca2 dependent K channels.
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On the other hand, there are complicated
oscillations that change dramatically with
changes in the applied excitatory current. Can
the known simple channels be responsible for the
complicated oscillations or is there some other,
as yet undiscovered, mechanism that is
contributing in an essential way?
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Ca2 in the external solution is essential for
the production of the complicated
oscillations Blocking the K channels also
prevents the complicated oscillations from
occuring. Perfusion of the fibers by EGTA, as
was done in the experiments, might cover up the
slow inactivation of some Ca2 channels
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The goal of the paper is to analyze the data
collected in experiments stimulating the muscle
fibers by current clamping, generating data from
a mathematical model that takes into account only
the K and Ca2 channels, and comparing the
resulting voltage responses.
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The results produced good agreement between the
experiment and the model -- that is, it appears
that the simple channels that have been shown to
be necessary for the behavior are sufficient to
explain it. The paper further analyzed the
mathematical model, as a dynamical system, to
explain why the system behaves as it does.