Where Does Pain Come From?

February 1st, 2010
Where Does Pain Come From?

Pain, in all its varieties and subtleties, is among the most complex of human symptoms. It has been described in uncounted ways by writers and portrayed by actors, but we read or view these characterizations through the lens of the pains we ourselves have had. Even though we all have felt pain, and in that sense have shared the experience with all other humans, it is also unique to us. Pain is both universal and profoundly personal. It’s a complicated subject.

Pain is not limited to humans, of course. All mammals certainly feel pain. Some aspects of the pain response reach far down below mammals in the animal kingdom to quite primitive creatures. How these creatures perceive it, if that is even the right word, is mysterious, but this observation tells us pain has been with us for many eons. That fact alone should tell us it must serve some important purpose.

All of us know that pain comes in many forms. There is the sharp pain from stepping on a tack. There is the vague, dull aching of a twisted knee, the cramping pain in the lower abdomen that comes with the flu, the pounding inside the skull of a migraine headache, the gnawing pain of a toothache. There is the restless pain that persists in spite of what positions you take, as well as the pain that only relents when you lie completely still. All of us could think of many more examples.

Pain is reported to the brain via a dense network of nerve fibers. Think of this network as an intricate grid of electrical wires.

The nervous system uses a series of switching stations to pass a signal from, for example, the end of your finger to your brain. The first of these are in the spinal cord. When you prick your finger, an electrical signal goes from a nerve fiber there, up your arm, and on to a relay station in the spinal cord in your neck. From there, it continues on up your spinal cord to your brain. What happens to it when it reaches your there is fascinating — and complicated.

Pain is a subjective feeling, meaning no one besides yourself can know precisely how you are feeling it. This means no two people will experience pain in the same way.

This variability in how pain is perceived, of the discomfort it causes us, is because the simple electrical signal running up your finger from that needle prick gets modulated by a maze of other nerve cells in the spinal cord and in the brain. Some of these influences dampen down the signal, others ramp it up. The result is when it finally gets to your upper brain, where your consciousness lies, all sorts of things have affected the signal, things that are unique to you and your brain.

We have two main approaches for treating pain: we can do things that reduce the pain signals coming from the spot that hurts, or we can use medications that confuse the brain into thinking the pain is either not there or is not so bad.

There are several simple things we can do to reduce the pain signals coming up the nerve fibers. A simple one has been known to parents for eons — simple rubbing of a painful spot. Stimulating one set of nerve fibers affects how our brain processes sensations. Stimulating the touch fibers in the same place where the pain is coming from causes them to intervene and dampen back the pain signal coming from the other fibers.

Cooling the area with an ice pack is another way to reduce the pain signals coming up the nerve network. Yet another is to put a medicine that interferes with how the nerves work right on the painful spot.

The other way to treat pain is to use medications that act directly on the nervous system to alter how the brain reacts to the signals coming up from the painful place. They convince the brain to downplay or even ignore the information.

More severe pain, such as from a broken arm, calls for medications more powerful than Tylenol or Motrin. Members of the opiate family, also called narcotics, are the standard. They all work in the same way: they go to the brain and the spinal cord and alter a person’s perception of the pain. They also can alter mood and a person’s level of awareness to things around them.

Even though we give narcotic medications for severe pain, a fascinating thing about them is that they are not really foreign to the body at all. We have similar substances that occur naturally in our body, and presumably these natural narcotics, called endorphins, are performing some useful function inside us, most likely involving pain control.

Pain, uncomfortable as it is, does serve some useful purpose, and in that sense helps a person heal. Pain alerts us that something is wrong and tells us we should try to do something about it. If we cannot feel the pain, worse injury often results.

But pain can also interfere with healing. Mild or moderate pain does not seem to affect healing much, but more severe pain, if it persists, can interfere with it. This stems from the effects of what we call stress hormones, substances like adrenaline, which the body releases at times of stress. They are called “fight or flight” hormones because they probably helped our ancient ancestors deal with things like a wild animal attack. Although they can help in times of acute danger, prolonged high levels of these hormones, such as occurs with continuing severe pain, do inhibit proper healing.