What Is It? Why Do We Have Pain?
Pain is a very subjective experience: what you feel isn't exactly the same as what someone else feels. Defining pain is difficult, then.
Because pain almost always has emotional and psychological components (in addition to physical pain), there is no objective test that can quantify the exact degree of pain a person is feeling.
But we all know pain when we feel it.
Types of Pain: Acute Pain and Chronic Pain
Pain can be divided into two main types: acute pain and chronic pain.
There's acute pain—short-lasting pain that was caused by, for example, crunching your finger in the car door. The nerves in your finger send a pain message to the brain, demonstrating main purpose of pain: to tell us when something is wrong in our bodies.
The pain signals sent by acute pain are helpful, and typically, acute pain goes away once the cause of the pain has been addressed.
However, pain can be chronic. Pain can linger long after the original injury or nerve damage, and chronic pain is typically defined as pain that lasts more than 6 months.
Pain can also be defined as chronic (or intractable pain) when there's no clear physiologic cause for the lingering pain. In these cases, the body continues to send pain signals even though there is nothing creating the need for the pain signal.
Definition of Pain
In 1973, the International Association for the Study of Pain (IASP) released a definition of pain that has stood for decades:
Pain is "an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.1
This broad definition encompasses both acute and chronic pain, and it even addresses the conundrum of chronic pain: it is unpleasant. It does have an emotional side, but there isn't always a known cause. However, it is undeniable that the patient is experiencing pain, even if the medical community can't say why exactly.
The IASP's general definition of pain is helpful, but it's interesting to note that there isn't a widely accepted definition of chronic pain specifically.
How Pain and Pain Signals Work
To understand pain and pain signals, you need a quick briefing in the body's nervous system.
There are two parts to the nervous system: the central nervous system and the peripheral nervous system. Through these two systems, nerves transmit messages to and from the brain.
The central nervous system is made up of the spinal cord and brain. Coming off the spinal cord is the peripheral nervous system; these nerves travel to every other part of your body to help you feel and move—and experience pain.
The peripheral nervous system has two further subsystems: the somatic nervous system and the autonomic nervous system.
The somatic nervous system nerves go to your bones, ligaments, tendons, muscles, and skin; the soma- in somatic means body in Greek. This is what helps you move and feel.
The autonomic nervous system is in charge of the involuntary functions of your body—breathing, heartbeat, digestion, and the other things that happen without you having to think about them.
If you damage any nerves—in any part of the body's nervous system—you can develop chronic pain. The nerves can start to malfunction; instead of sending pain messages only when there's an appropriate stimuli, they can start to send pain messages all the time.