Changes in myelin structure and fatty-acid tail ordering upon nerve fiber excitation

Abstract

Using laser interference microscopy and Raman spectroscopy of frog myelinated nerve, it has been found that upon a train of action potentials passing along the fiber, the phase height (refractive index) of paranodal myelin declines while the ordering of fatty-acid tails therein increases. In contrast, at the node of Ranvier where excitation is generated, both the phase height of the axoplasm and the ordering of axolemmal lipid tails decline. It is supposed that such changes in myelin are caused by desorption of membrane-bound Ca2+.