Action Potential

Joseph T. Ho jtho at
Thu Dec 12 03:24:55 EST 1996

Saltatory conduction basically is what happens when axons are myelinated.  The
myelin acts as an insulator between the nodes of Ranvier.  These nodes are
areas of the axon that are not covered by the myelin sheath.  A depolarization
of the membrane "jumps" from node to node.  Because of the increased
insultation, there is a high resistance across the axon membrane.  The
depolarization travels between the nodes basically instantaneously, like
electricity in a wire.  It is only at the nodes that the action potential is
regenerated, because on these areas have the voltage-gated Na channels, etc.

If this doesn't make sense then perhaps someone else can explain it.  This was
my first attempt at explaining it to someone else. :)

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

Loren A. Evey (lae2 at wrote:

: > > How does an impulse travel down an axon in action potential
: > 
: Major snip
: > At the end of the journey, at the synaptic terminal, the voltage 
: sensative
: > sodium channels are joined by voltage sensative calcium channels, and 
: it
: > is the influx of calcium that is responsible for causing the
: > neurotransmitters, packages in little membrane vesicles, to be released
: > onto the next cell.  That next cell may be another neuron, and the 
: whole
: > thing could start again at the next cell, and so on ...
: > 
: > Hope that helped.
: > 
: > Matt

: Excellent, would you extend your explanation to include saltatory 
: conduction?  Thanks.

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