Axonal transport: The orderly motion of axonal structures.

Axonal transport is a constitutive process that supplies the axon and axon terminal with materials required to maintain their structure and function. Most materials are supplied via three rate components termed the fast component, slow component a, and slow component b. Each of these delivers a distinct set of materials with distinct transport kinetics. Understanding the basis for how materials sort among these rate components and the mechanisms that generate their distinctive transport kinetics have been long-standing goals in the field. An early view emphasized the relationships between axonally transported cargoes and cytological structures of the axon. In this article, I discuss key observations that led to this view and contemporary studies that have demonstrated its validity and thereby advanced the current understanding of the dynamics of axonal structure.