Anatomy of Chronic Pain

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To understand chronic pain, you need to understand the anatomy of your nervous system. Through the nerves, the nervous system transmits message to and from the brain, and it's a very complex system.

The central nervous system is the spinal cord and the brain. Branching off the spinal cord is the peripheral nervous system; either the central or peripheral nervous systems can be affected in neuropathic pain, which is a type of chronic pain caused by a malfunction of nerves.

spinal cord and nerve structures

The peripheral nervous system has 31 pairs of nerve roots that extend from the spinal cord to the various parts of the body. These nerves help you feel (those are the sensory nerves) and move (those are the motor nerves).

Following is a chart that shows you how many pairs of spinal nerves are at each level of the spine.

SPINAL CORD 31 Pairs – Spinal Nerves
Cervical 8 pair
Thoracic 12 pair
Lumbar 5 pair
Sacral 5 pair
Coccyx 1 pair

The peripheral nervous system is further divided:

  • The somatic nervous system has nerves that go to the musculoskeletal system (bones, ligaments, tendons, muscles) and the skin. It's what helps you feel; these nerves are part of what help you feel pain.
  • The autonomic nervous system runs the "involuntary" functions of your body. That means that it makes sure your heart keeps pumping and you digest your food right—without thinking about it.

If you damage any nerves, you may develop chronic pain. They're responsible for sending pain messages, so if they're damaged, they may send a continuous stream of pain messages.

Nociceptors are another important part of your nerves, and you need to understand them if you want to understand certain types of pain. Nociceptors are receptors at nerve endings, and they are activated when something happens that triggers pain. For example, if you slam your finger in the car door, the nociceptors in your finger will turn on and send a pain message via the peripheral nerve to the spinal cord and on to the brain. Two seconds before you slammed your finger, though, the nociceptor was not active because there was no stimulus (in this case, injury) making it respond.

It's thought that one cause of chronic pain may be malfunctioning nociceptors. Even if there's no direct cause, they may be constantly sending pain messages to the brain. Continuing the above example, say that your finger healed after you slammed it in the door but you continue to feel pain. The nociceptors on your finger's nerves may be malfunctioning in this case; they may still be sending pain messages. That can result in chronic pain.

Updated on: 04/07/16
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Symptoms of Chronic Pain
Steven Richeimer, MD
This article was reviewed by Steven Richeimer, MD.
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