Transcript Document

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.
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