multiple sclerosis

Joseph T. Ho jtho at
Fri Oct 25 21:16:27 EST 1996

MS is due to demyelination in the CNS.  Myelin insulates the axons.  As the
amount of myelin around an axon is decreased, the capacitance goes up (more
charge is required for the same potential difference).  This means that it
becomes more and more difficult for an action potential to propagate through
this region of the axon.  Once the amount of myelination falls down to about
2% in an area, basically no action potentials can get across that area.

Stimulating a nerve more would most likely increase the frequency of action
potentials.  However, action potentials are basically non-graded.  That is, as
long as you reach threshhold, the action potential will fire and reach about
the same voltage each time.  This of course could be a different story if you
were to do something extremely artificial like stick an electrode in the
axon.  In fact, I think increasing the voltage change would have less to do
with a solution than increasing the current.

NOTE: I am certainly no expert in this. This is what I have picked up in my
first 5 weeks of med school :)

Joseph T. Ho ( jtho at )
University of Washington School of Medicine, MS I

John King (johnkate at wrote:
: Is the cause of signs for MS due to demyelination?  Is it due to
: decreased nerve conduction?  Could nerve conduction increase if the
: nerve was stimulated more?

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