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Saltatory Conduction

This page offers a metaphor for understanding how myelin speeds up the propagation of action potentials.

Imagine a very long, thin water-balloon lying on the ground in front of you.  The balloon represents an UN-myelinated axon.

Now imagine another water-balloon enclosed within long, tight-fitting segments of pipe.  In between the segments of pipe are short stretches, about as wide as your foot, where the balloon is naked.  Now the balloon represents a myelinated axon; the pipe is myelin and the short naked stretches correspond to nodes of Ranvier.

BACKGROUND and EXPLANATION:  This metaphor may appear silly, but the physics is actually plausible.  It is based on a respectable hydrodynamic model for electricity, in which water pressure corresponds to voltage, flowing water corresponds to electric current, and elasticity of the balloon corresponds to capacitance. 

David KingComments and questions: dgking@siu.edu

SIUC / School of Medicine / Anatomy / David King

Last updated:  29 December 2006 / dgk