Axons

by Karin Sorra

Axons typically project over long distances from their sites of origin to communicate and synapse with their targets. Swellings termed axonal varicosities / boutons are typically the sites where synapses occur. Boutons form as terminal bulbs at the end of an axon, and/or along the length of individual axons as boutons en passant (see diagram left). Axonal bouton, varicosity, en passant terminal or bouton are terms often used interchangeably, although they may exist as slightly different morphological entities.

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Axon Coursing Through Apical Dendrites of a CA1 Pyramidal Neuron

An axon can be either myelinated or unmyelinated. Within the central nervous system, glial cells termed oligodendrocytes form the myelin sheath around axons and serve to facilitate synaptic transmission along their length. Oligodendrocytes are non-neuronal cells and their cell bodies can be found within hippocampal area CA1.