Chapter 12.3, Problem 3AYLO

Summary Introduction

To discuss:

How fiber diameter and the presence or absence of myelin affect the conduction speed of a nerve fiber.

Introduction:

The nerve fiber is insulated by a spiral layer called myelin, which is produced in both central nervous system (CNS) and peripheral nervous system (PNS). The formation of myelin is called myelination or myelinogenesis. Schwann cells spiral a single nerve fiber repeatedly forming hundred compact layers without cytoplasm between the plasma membrane. These layers form the myelin sheath. This myelin sheath is absent in unmyelinated nerve cells. Each gap between adjacent Schwann cells in the myelin sheath of a neuron is called as nodes of Ranvier or myelin sheath gap.