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2014 ; 276
(ä): 126-34
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Regulation of conduction time along axons
#MMPMID23820043
Seidl AH
Neuroscience
2014[Sep]; 276
(ä): 126-34
PMID23820043
show ga
Timely delivery of information is essential for proper functioning of the nervous
system. Precise regulation of nerve conduction velocity is needed for correct
exertion of motor skills, sensory integration and cognitive functions. In
vertebrates, the rapid transmission of signals along nerve fibers is made
possible by the myelination of axons and the resulting saltatory conduction in
between nodes of Ranvier. Myelin is a specialization of glia cells and is
provided by oligodendrocytes in the central nervous system. Myelination not only
maximizes conduction velocity, but also provides a means to systematically
regulate conduction times in the nervous system. Systematic regulation of
conduction velocity along axons, and thus systematic regulation of conduction
time in between neural areas, is a common occurrence in the nervous system. To
date, little is understood about the mechanism that underlies systematic
conduction velocity regulation and conduction time synchrony. Node assembly,
internode distance (node spacing) and axon diameter - all parameters determining
the speed of signal propagation along axons - are controlled by myelinating glia.
Therefore, an interaction between glial cells and neurons has been suggested.
This review summarizes examples of neural systems in which conduction velocity is
regulated by anatomical variations along axons. While functional implications in
these systems are not always clear, recent studies on the auditory system of
birds and mammals present examples of conduction velocity regulation in systems
with high temporal precision and a defined biological function. Together these
findings suggest an active process that shapes the interaction between axons and
myelinating glia to control conduction velocity along axons. Future studies
involving these systems may provide further insight into how specific conduction
times in the brain are established and maintained in development. Throughout the
text, conduction velocity is used for the speed of signal propagation, i.e. the
speed at which an action potential travels. Conduction time refers to the time it
takes for a specific signal to travel from its origin to its target, i.e.
neuronal cell body to axonal terminal.
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