The 1-2-3 of CHRONIC PAIN
So how do you go from stubbing your toe to saying “Ouch, that hurts” a mili-second later.
Doctors believe that we have three levels of pain processing within the body: from 1) the site of injury; to 2) the spinal cord; to 3) the brain. This is the body's natural circuit to pass along the pain signal. Lets take a look at each step.
1) SITE OF INJURY
Our skin, our muscles, our bones all have millions of tiny pain receptors that get activated when we touch something hot, sharp, etc. The offending agent (like a knife) will cause an injury that leads to increased levels of little molecules (like Prostaglandins, Leukotrienes, Histamine, Bradykinin, Substance P and others). The release of all these molecules is a well-known process called "inflammation". One aspect of "inflammation" is that our pain receptors get activated, and we say ouch (other aspects of inflammation include dilation of blood vessels that makes an inflamed area red, hot, and swollen).
These pain receptors are found at the end of “peripheral nerves”. We have many many peripheral nerves, which start around the spinal cord and travel all the way down our arms and legs to reach different spots along our body. They carry the “pain information” from your finger tip to your spine.
There are two kinds of peripheral nerves:
a) Delta nerves: which transmit pain very quickly, and the pain they report is sharp; the other nerve is b) C-fibers: which transmit pain at 10% the speed, and they report vague, achy pain.
Once the “pain information” arrives at the spine (it arrives after a long trip along the peripheral nerve), it gets handed off to a new nerve, a “central nerve”. The central nerve is located entirely within the spinal cord, and it takes the pain information from the spine (at the spinal level nearest the injury) to the brain. The Hand-Off of the pain information from the peripheral nerve to the central nerve is very complex.
There are some nerves travel from the brain to this hand-off site (they send information in the opposite direction as the pain information), and they can affect how much pain information gets passed along at the Hand-Off.
Our brain is the final destination of the “pain information” that started all the way back in our stubbed toe, or broken wrist for example. The brain is where we process information and where we realize that something hurts, and we say “Ouch”.
Our brains perception of pain is affected by other nerves within the brain. Meaning some brains are more sensitized to pain information that other brains. That is why doctors believe people with depression or anxiety disorders are at more risk for developing chronic pain. Their brains are primed, ready to be overwhelmed by pain information.