Library · Physiology
Nerve regeneration
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A peripheral nerve is a bundle of axons, the long extensions neurons use to send their signal. When one is injured, the piece of axon beyond the cut almost never survives: it breaks down in a process called Wallerian degeneration, which starts within a few hours.
What follows is a job of cleanup and signaling. Schwann cells, the cells that wrap around the axon, and then macrophages, the cells that eat up debris, clear away what is left. And those same Schwann cells line up single file inside the endoneurial tube, the sheath that surrounded the axon, forming what are called bands of Büngner. The cable burns out but the conduit stays, and the new wire follows it to the far end.
Following that guide, the axon regrows at a rate of about one millimeter per day, with a range of half a millimeter to three millimeters.
If the injury destroyed that architecture too, things change: axons can enter the wrong tube and end up where they were not headed, and that hampers regeneration across the board.
In brief
In nearly every injury, the distal segment of the axon dies by Wallerian degeneration, which starts hours later.
Schwann cells and macrophages clear the debris, and the Schwann cells form bands of Büngner inside the endoneurial tube.
The cable burns out, the conduit stays, and the new wire follows it.
The axon regrows along that guide at roughly one millimeter per day, with a range of 0.5 to 3.
If the injury destroyed that architecture, axons can be misrouted into the wrong tube, and that hampers regeneration.
Sources (2)
- National Center for Biotechnology Information, StatPearls PublishingPeripheral Nerve Injury, StatPearlsPublished
- National Center for Biotechnology Information, StatPearls PublishingHistology, Schwann Cells, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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