Most of the time pain acts as a critical part of our sensory system, and is therefore a necessary though unpleasant function of a healthy body.  However, it’s becoming increasingly obvious that chronic pain may be more like a disease or pathology of the nervous system related to abnormal reactions in the brain and spinal cord.
In this light, chronic pain is both a common and serious medical condition.  Chronic pain is serious because of the effect it has on every facet of people’s lives and because for many individuals, cures are unattainable.  It is medical because, in its root cause, chronic pain is obviously connected with the body and the brain.
Acute pain is that initial feeling of caution and hurt that all of us experience.  It tells us immediately when we’re injured and let us know the location and most often even the amount of damage that might have occurred.   It activates our protective systems of withdrawals (taking your hands out of the fire), remainder (to allow the injured area to cure), protection (tensing up areas around an accident to prevent re-injury), avoidance (fears of the context of the injury to stop doing it again), and even warning to others (shouting out).  These are all crucial activities for survival.
It’s important to keep in mind that these properties of acute pain in order to better understand chronic pain.  A variety of methods are used to attempt to help people manage chronic pain.  Although this management approach differs from that of acute pain, keep in mind that the physiological system inherent is the same.
So regardless of how much you read or are told about the differences between acute and chronic pain, and no matter how much you tell yourself that chronic pain doesn’t mean something is horribly wrong (it is “hurt but not hurt”), chronic pain may still mostly “feel” like tissue damage and trauma.  This does not mean that you can’t better manage and even decrease the severity and impact of pain in your life, since in fact you can.
Nevertheless, the optimum pain management approach is not based on willing pain away, or pretending it isn’t there, but rather on making best use of the growing scientific understanding of the pain is communicated and modulated (altered or modified) in the human body and brain.
Chronic pain
Chronic pain, which is often defined as continuous or intermittent pain lasting more than six months, afflicts an estimated 30 million to 50 million Americans.  The societal costs in disability and lost productivity totaling over $100 billion annually.
Pain is the number one problem that brings patients to doctors, and to complementary or alternative medicine (CAM) practitioners.  The tremendous suffering brought on by chronic pain isn’t measurable in dollars and virtually all of us know at least one person who’s struggling with chronic pain.
Pain contributes to disability and psychological suffering.  Additionally, evidence is accumulating that some kinds of chronic pain may be detrimental to both the nervous system and even the immune system.
Although much remains to be understood, research over the past 3 decades has revealed key information about pain and our bodies’ response, and this has led to improved treatment in many areas. They react exclusively to tissue-damaging stimuli like, excessive heat, cold, tearing, or stress.  Various chemicals, like prostaglandins and stress-related hormones, can sensitize nociceptors.  (Aspirin-type pain relief medicines (NSAIDs) work by blocking the prostaglandins.)The pain signal then travels along specific nerve pathways to the part of the spinal cord called the dorsal horn.  From that point, the pain ascends to a variety of brain structures.
Though this pain transmission system was once thought to operate like an old-time telegraph (messages input at one end and arrive in the other), we now know that the system is much more like a computer
.In order to enable our body to have the best information when it’s needed, signs coming in are highly modulated.  This implies pain signals from certain areas can be amplified, suppressed, or altered in quality from the spinal cord or brain.
For the most part this works to our great advantage.  For instance, after stubbing your toe, the pain, which can be an acute signal to check for damage, quickly dulls.  This is an active process of pain suppression to allow us to return to other activities.  In a similar manner, most of the activity going on in our gastrointestinal tract (including quite large muscle contractions) isn’t felt due to active suppression.  On the other hand, the pain may continue to remind us to avoid active usage in an injury in which movement could be harmful.
The gate-control theory states that neural impulses, evoked by injury, are influenced from the spinal cord by other nerve cells that act like gates, either preventing the impulses from getting through, or facilitating their passage.  To put it differently, the brain is not a passive receiver of pain advice but can influence the information obtained.
The description of our built-in pain modulation system (known as the gate control theory) by Drs. Melzack and Wall in 1965 and the subsequent discovery of inner opiate-type chemicals (including the endorphins) were major first steps in a fuller comprehension of pain control within the body.
More recently, many more parts of the complex system have been discovered, in addition to new chemical transmitters and interactions between pain modulation and other pieces of our sensory and emotional brain systems.
Pain and threat
We’ve known for a long time that pain isn’t a simple sensation and it is intimately linked with our inborn emotional systems for detecting and responding to threat.  This way it is closely tied to the same anxiety or “fight or flight” system that responds to outside threats.  Any sound or thing may be associated with a fear reaction, but pain is unique in that it always has a negative psychological quality (unpleasantness) and is closely associated with emotions of fear and anxiety.
The ability of learned associations between particular painful sensations and emotional reactions is dramatic.  Once set in place, these conditioned responses operate regardless of the context and without conscious input.
In a similar way, pain or even the circumstance — the time, place, or situation — surrounding a debilitating episode may perpetuate a pain-fear-pain cycle.  Some of the brain circuits underlying this pain-fear cycle have recently been made clear with functional brain imaging for pain problems both in the inner organs and the rest of the body.
Connections between the psychological and pain systems may also account for the frequently successful use of anti-anxiety and anti-depression drugs to treat chronic pain.
Chronic pain management In chronic pain we have strong evidence that our pain modulation process is not working well.  Rather than suppression, the system may be over-sensitized so that normal sensations activate pain transmission and suffering.  Because of the pain, individuals might also have increased levels of depression and anxiety, diminished quality of life, fear of further pain and impairment, sleep loss, and withdrawal from social and pleasurable activities.
The above discussion might cause you to feel helpless in the face of such an important and strong physiological system that has gone astray.  The better news is that both ancient and modern medicine has evolved a variety of approaches to help cope with chronic pain — and perhaps even return the system to more normal functioning.