Regeneration of nerves.

Bill Browning bbrownin at
Sun Oct 20 23:34:15 EST 2002

Professor Norman,
     Thanks for your explanation of nerve regeneration; you answered all of
questions clearly.
     My friend fell on a broken tree branch and impaled his fore arm.  He is
excellent care from a hand surgeon at Brigham & Womens Hospital.  The injury
close to his ulnar nerve but the functions of his fingers is not affected.
He has
numbness in the skin of his fore arm; and they tell him that may or may not
go away.
     Your explanation helps us understand what is going on.
     And it gives me the necessary information in case I ever have to
emergency nerve surgery!
Bill B.
"Richard S. Norman" <rnorman at> wrote in message
news:dte5ru4kesdtfg73ppi0li2bjvplsk5rnf at
> On Sun, 20 Oct 2002 00:52:02 GMT, "Bill Browning"
> <bbrownin at> wrote:
> >Regeneration of nerves.
> >     When a severed hand is reattached, how is the nerve restored?  Do
> >nerve bodies form and grow new axons?  Do the old axons rejoin their
> > segments?  Do the proximal parts of the old axons extend along the
> > route of the nerve?  How do the new nerves find the right places?
> > Does the sensation starting at the thumb give a sensation associated
> > with the thumb or is it random and the patient learns how it works?
> >Bill B.
> When a peripheral nerve is severed, the axons degenerate back to the
> cell bodies in the spinal cord (or the dorsal root ganglia, for
> sensory cells).  Then the axons regrow back along the old pathways. If
> the cut ends of the nerve are sutured together or are joined in some
> other way, then it is possible for at least some of the growing axons
> to find their way back to their original targets. The cells "know"
> (through chemical signals) just where they "belong" and preferentially
> reform the same functional connections they had originally, if
> possible.  However, the axons can innervate the wrong muscles or "get
> lost" along the way.
> If the original contact is re-established, then the function is simply
> restored.  Otherwise, either you relearn or else the function remains
> lost.  It is very variable -- sometimes a surprising amount of
> function is regained, sometimes a dissappointing amount is lost.
> See "peripheral nerve  regeneration" on, for example.

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