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Following signposts

As the growing axon winds its way through the developing embryo, long- and short-range chemical signals guide it. Some chemicals work by attracting the growth cone at the tip of the axon, and others by repelling it. Long-range signals come from the targets - like beacons, and short-range signals from 'signpost' cells along the way. Like real signposts, these signals tell the axon where to turn or stop.

A growing nerve ending.
A growing nerve ending.
David Becker/Wellcome Photo Library

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