The body's system for processing the sensation of pain is very complex and involves many different levels. Each level may either amplify or suppress messages from an area of injury. When strong pain messages run unchecked through the body, they can end up doing further harm to the body as a whole, causing, for instance, the stress response or the evolution of chronic pain.

Pain medication and other techniques target these various levels of processing in an effort to help increase the body's own ability to limit the consequences of tissue injury and pain.

One level of pain processing is where the pain messages are sent between the area of injury (surgical site or bone fracture) and the spinal cord. Basic and clinical research has led to exciting progress that allows us to reliably change the pain messages at this level. Let's look at what happens when tissue injury occurs.

Tissue damage turns on a cascade of nerve messages to the spinal cord

When an injury happens (cut, crush, fracture), local tissues are disturbed. Special pain-sensitive nerve endings are directly stimulated by the injury or indirectly stimulated from chemicals released by the damaged cells. These nerve endings send messages along the nerves to the spinal cord.

A cascade of nerve messages travels from this zone of tissue damage to a specific area in the spinal cord that acts like a relay center where the nerves connect with other specialized nerves in the spinal cord. These, in turn, connect to many other nerves, sending signals up and down the spinal cord.

The excited specialized nerves in the spinal cord then send messages back down to the area of injury, but now covering a wider area. This returning signal causes the common effect of local tenderness, swelling, and muscle spasm. The excited spinal cord simultaneously relays these messages up to the brain, causing us to perceive the pain.

This whole process occurs quickly and is the normal sequence of events designed to protect us from further tissue injury. Because of the returning round of messages from the nerves, a wider injured area becomes painful to touch, muscle spasm slows down normal movement, blood pressure may rise, and we may break out in a cold sweat. Although this may protect the area after an accident, it is hardly the situation we would desire after in other situations (e.g., after surgery).

The sensation of pain is different for different areas of the body. The skin has many pain receptors that are able to send detailed information that will tell the brain exactly where the pain is and what the pain is like. For other areas of the body such as internal organs, there are fewer pain receptors and the receptors are not able to send very precise messages. Therefore, internal pain can be difficulty to pinpoint.

In some cases, pain can be felt in a different part of the body than where the cause is because nerve impulses from different areas of the body can share the same nerve pathways. This is called referred pain. For example, pain from gallstones may radiate to the right shoulder and stimulation of nerves in the throat and mouth can cause "ice cream headache."

Everyone responds to and experiences pain differently. The difference in pain response can be due to:

  • age
  • cultural or religious expectations
  • current emotional status
  • general medical status
  • pre-existing pain problems
  • prior experiences and expectations regarding pain.

All of these factors can affect how pain is experienced. For example, if you know someone who had the same condition as you and was comfortable, you may not feel as worried or fear pain as much as if you know someone who has pain and distress. Fear and other emotions can intensify the perceptions of pain.

Finding out more information about your situation and discussing it with your doctor will often help you understand that virtually all pain can be controlled. This will ease much of your fear and anxiety, and will also help ease some of your pain.

Other emotions that you're feeling as a result of the illness can also have a significant effect on your perception of pain, and are worth addressing and discussing.

By understanding the processes and experience of pain, we are able to prevent and treat pain more effectively.