$Unique_ID{BRK00849}
$Pretitle{Ill Defined Symptoms and Rare Diseases}
$Title{What Causes Pain?}
$Subject{pain causes types}
$Volume{N-2}
$Log{}

Copyright (c) 1991   Tribune Media Services, Inc.


What Causes Pain?


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QUESTION:  It seems that I suffer from pain in different ways, and the hurt
feels different at various times.  What causes pain?  Is it possible that
there are different nerves involved?

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ANSWER:  Pain is caused by overstimulation of nerves that may or may not
conduct the stimulus to the central nervous system, meaning the brain and
spinal cord.
     Depending on the type of stimulus, pain impulses can travel through two
different types of nerves that are quite different in structure and entirely
independent.  For example, a pinprick sensation (also called fast pain or
first pain) travels through small nerve fibers with a myelin sheath or
covering like an insulated cable.  Deep pain (also called muscle pain or
second pain) occurs when you have a muscle cramp or more severe muscle damage.
This type of pain travels slower and is conducted by larger nerve fibers that
lack the myelin sheath or covering found on smaller nerve fibers.
     Thus there are two types of pain receptors, and the two types of fibers
are specific for such pain.  Pain is never due to overstimulation of other
types of receptors.
     The different types of pain may be demonstrated by inflating a blood
pressure cuff (or tourniquet) around a limb to restrict its blood flow, then
inducing pain first by a pinprick (first pain), then by pinching a full
thickness fold of skin (second pain).  If the lack of blood flow (ischemia) is
maintained by the cuff, the pinprick sensation will disappear while the
pinching or muscle cramp type pain will remain, and is usually increased and
feels more painful.
     Because there are two different reflex actions--a rapid withdrawal after
pinprick and muscle contraction and immobility after pinching--it is obvious
the central circuits from two different types of fibers for two different
types of pain must be different.
     It would be impossible for the same circuit to produce reflex responses
that are almost opposite in nature:  immediate withdrawal and fairly rapid
loss of pain versus a dull cramp-like pain that persists associated with
muscle contraction and actual tissue damage.
     This information helps physicians prescribe the most effective analgesic
for the particular type of pain that is causing the misery.
ÿ
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The material contained here is "FOR INFORMATION ONLY" and should not replace 
the counsel and advice of your personal physician.  Promptly consulting your 
doctor is the best path to a quick and successful resolution of any medical 
problem.
