why is the nerve tender to touch?

Richard Norman rsnorman at mediaone.net
Tue Feb 27 23:33:10 EST 2001


"satish gore" <sgore at stanford.edu> wrote in message
news:3A9C35D9.C60866B at stanford.edu...
> Hi
> i had a basic query,
> why does a painful nerve become tender?
> what is the molecular mechanism?
> any thoughts welcome!
>
> satish gore

I am not sure what you mean by a "painful nerve".  Do you
literally mean a neurological problem in the nerve itself
that causes pain (like Trigeminal neuralgia, for instance)?
And what do you mean by "touching" the nerve.  Certainly
not touching the actual nerve with your finger.  Do you mean
pressing on the nerve itself or on a "tender" tissue area?

If you mean why does an area of tissue become "tender" so
that touching or pressing on it cause pain, the question is
a bit circular.  The "tenderness" means that touching or
pressing it causes pain.

Most likely, some tissue damage causes (and is caused by)
physical damage to cells, anoxia, changed extracellular
osmotic pressure/ion concentration/pH etc. These "irritate"
sensory cells in the area causing them to generate excessive
numbers of action potentials to minor stimuli.  The pain cells
also can have lower threshold so that even mild stimuli
activate them.

The tissue damage also triggers an immune response
resulting in histamine release in the area.  This triggers
the inflammatory response including excessive
capillary dilation and redness/heat/swelling/pain (rubor/
calor/tumor/dolor).  The histamine also induces the
sensation of pain.

As a result, you tend to avoid using that damaged part
of the body for a while, giving it an opportunity to heal.








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