Understanding pain

You know what it's like to feel pain. Its unpleasantness can take many forms, whether it's the smart of a burn, the daily ache of arthritis or a throbbing headache. What you might not be aware of is the science behind why you hurt.

Pain involves a complex interaction between specialized nerves, your spinal cord and your brain. Imagine a complicated traffic system, with on-ramps, different speeds, traffic lights, varying weather and road conditions, a traffic control center, an emergency response system, and more. And the vehicle you're in also makes a difference, because the experience of pain varies from one person to another.

Pain is both physical and emotional. It involves learning and memory. How you feel and react to pain depends on what's causing it, as well as many personal factors.

Acute versus chronic pain

There are two major categories of pain. Pain can be short term (acute) or long term (chronic):

  • Acute pain is a severe or sudden pain that resolves within a certain amount of time. You might feel acute pain when you have an illness, injury or surgery.
  • Chronic pain is persistent, lasting for months or even longer. Chronic pain is considered a health condition in itself.

With acute pain, you typically know exactly where and why it hurts. Your elbow burns after a scrape or you feel pain at the site of a surgical incision. Acute pain is triggered by tissue damage. Its purpose is to alert you to injury and protect you from further harm.

With chronic pain, you might not know the reason for the pain. For example, an injury has healed, yet the pain remains — and might even become more intense. Chronic pain can also occur without any indication of an injury or illness.

Causes of pain

At the most basic level, pain begins when particular nerve endings are stimulated. This might result from damage to your body tissues, such as when you cut yourself. Pain can also result from damage or disruption to the nerves themselves. Sometimes pain occurs for no known cause, or long after an injury has healed.

Pain can affect any part of your body. Some of the most common forms of pain are back and neck pain, joint pain, headaches, pain from nerve damage, pain from an injury, cancer pain, and pain-related conditions such as fibromyalgia (a disorder that causes widespread musculoskeletal pain).

Pain from tissue damage

Pain is your body's way of alerting you to danger and letting you know what's happening in your body. You perceive pain through sensory nerve cells. These are the same type of cells that transmit information from your senses, allowing you to smell, see, hear, taste and touch.

The nerve cells that respond to pain are part of the peripheral nervous system — which includes all of the body's nerves except those in the spinal cord and brain (the central nervous system). Peripheral nerve cells align into a network of fibers that carry messages from skin, muscles and internal organs to your spinal cord and brain. The messages take the form of electrical currents and chemical interactions.

Illustration of how nerves run through the body

The peripheral nervous system is all the nerves in your body, aside from the ones in your brain and spinal cord. It acts as a communication relay between your brain and your extremities. For example, if you touch a hot stove, the pain signals travel from your finger to your brain in a split second. In just as short a time, your brain tells the muscles in your arm and hand to snatch your finger off the hot stove.

The peripheral nerve fibers have special endings that can sense different types of harmful stimuli — anything that damages or threatens to damage tissues in your body. It could be a cut, pressure, heat, inflammation, even chemical changes. Injuries, illnesses and surgery all can cause tissue damage.

These specialized nerve endings are called nociceptors (no-sih-SEP-turs). You have millions of them in your skin, bones, joints, muscles and connective tissues, as well as in the protective membranes around your internal organs.

In response to tissue damage, nociceptors at the source of the injury relay pain messages in the form of electrical impulses. These pain messages travel along a peripheral nerve to your spinal cord.

This type of pain is referred to as nociceptive pain. It may be mild or severe. It may be sharp, stabbing, throbbing, burning, stinging, tingling, nagging, dull or aching. Ouch!

July 26, 2016