The node of Ranvier in CNS pathology.

I Lorena Arancibia-Carcamo,David Attwell

doi:10.1007/s00401-014-1305-z

Abstract

Healthy nodes of Ranvier are crucial for action potential propagation along myelinated axons, both in the central and in the peripheral nervous system. Surprisingly, the node of Ranvier has often been neglected when describing CNS disorders, with most pathologies classified simply as being due to neuronal defects in the grey matter or due to oligodendrocyte damage in the white matter. However, recent studies have highlighted changes that occur in pathological conditions at the node of Ranvier, and at the associated paranodal and juxtaparanodal regions where neurons and myelinating glial cells interact. Lengthening of the node of Ranvier, failure of the electrically resistive seal between the myelin and the axon at the paranode, and retraction of myelin to expose voltage-gated K+ channels in the juxtaparanode, may contribute to altering the function of myelinated axons in a wide range of diseases, including stroke, spinal cord injury and multiple sclerosis. Here, we review the principles by which the node of Ranvier operates and its molecular structure, and thus explain how defects at the node and paranode contribute to neurological disorders.

Highlights

Delivery of information is essential for the proper function of the nervous system
The axon down which the action potential travels is wrapped by myelin, which is produced by oligodendrocytes in the central nervous system (CNS) and by Schwann cells in the peripheral nervous system (PNS)
Action potential propagation along myelinated axons is dependent on healthy nodes of Ranvier

Summary

Introduction

Delivery of information is essential for the proper function of the nervous system. The axon down which the action potential travels is wrapped by myelin, which is produced by oligodendrocytes in the central nervous system (CNS) and by Schwann cells in the peripheral nervous system (PNS). This myelin sheath increases the effective resistance of the axonal membrane, lengthening its electrical space constant and promoting signal spread along the axon. Paranode Juxtaparanode less charge (in the form of Na+) needs to enter to depolarize the cell. Both of these effects increase the action potential conduction speed. The reduction of Na+ entry leads to less ATP being used by the axon on Na+ pumping, thereby allowing the conduction of the action potential to be more energetically efficient for the axon, at the expense of more energy being used to maintain the resting potential of the ensheathing oligodendrocyte [55]

Objectives

Conclusion