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Regeneration of nerves.

Thalamus zhil at online.no
Sat Oct 19 20:31:40 EST 2002


I am not a Medical Doctor, but a student if you will.

"Bill Browning" <bbrownin at nospamverizon.net> skrev i melding
news:S6ns9.11371$Pk1.8084 at nwrddc02.gnilink.net...
> Regeneration of nerves.
> When a severed hand is reattached, how is the nerve restored?

No, not unless the neurons are _forced_ one way or another.
Thus there wouldn't be anybody with a handicap, IE if they break their
spine.
But genetic reprogramming could potentially restore via viral vectors neural
pathways.

> Do new nerve bodies form and grow new axons?

No, and potentially yes in some cases, although they use stem cells.

> Do the old axons rejoin their segments?

No.
In some cases the destruction of a terminal will create a cascade of
destruction.
And they uses this mehode to find pathways from limbs/segments in certain
species through/to the spine, with chemical tracers (histology).

> Do the proximal parts of the old axons extend along the route of the
nerve?

If the nerve is cut, then the axon degenerates, and the cellbody (soma) with
it in some cases.
You're thinking of a 'replacement', right ?
So the neuron needs information that it should create a new growth-cone to
find it's way through the former pathway, and this means viral vectors if
I'm not mistaken.

> How do the new nerves find the right places?

Usually during developement, the growth-cone finds it ways through variuos
cues (chemical etc.).
There are several different ways (attraction/deflection), and it usually
happens when the neuron is beginning to specialize, but after it is full
grown it is difficult for it to repair or repeat the procedure unless nature
has evolved a way to regenerate neural pathways (which I'm sure exists
somewhere..........).

> 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.

Well, if the 'wiring' isn't screwed up, and the pathway has regenerated, the
sensation will not differ very much from previous experiences.
Ever heard about the 'phantom'-limb ?
It is the memory of how the neural network used to be experienced.
So, a repaired neural pathway should be exactly as the old one.

Brian
PS.Before I began to study in small part neural science, I didn't knew how
things work, but now I'm seriously impressed by how the neural metworks
operate.
The question of consciousness is still a mystery, yet.
And I think that I'll remain ignorant, because so many things are
developing; there simply won't be enough time to fully realize everything
every single aspect of neural science, thus the specializing.
But I think it is worth a try to study the subject, even for a layman like
me.





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