The pain sensation begins as a chemical signal which is given out by pain-sensing nerve endings called nociceptors. These signals travel through the group of peripheral nerves that run throughout the body to the central nervous system, the brain and the spinal cord.

There they collect in the dorsal horn, a place in the spinal cord that is like a clearing-house for pain messages. The signals are passed through to the brain’s thalamus, which sorts then out and passes them to the cerebral cortex, the place where the pain is really felt.

ACUTE PAIN

Acute pain is a sharp, direct pain which comes from an injury to tissue but can also be triggered by a harsh illness.

1. Nociceptors in the peripheral nerves sense the injury and react by releasing chemical messengers.

2. The messengers move through very fast nerve channels to the spinal cord, where...

3. ...they are passed straight to the thalamus and into the cerebral cortex.

4. The brain accurately identifies the location of the injury and sends a message back down to the spinal column telling the muscles to contract and block the pain. The process can take place immediately for example when your finger touches a hot stove and reacts quickly by pulling away.

CHRONIC PAIN

Chronic pain is continual, unbearable pain, such as that can occur from a bad back or diseases of the nerves themselves, it takes a more indirect direction.

1. Pain signals go into the dorsal horn of the spinal cord

2. ...and move back and forth among nerves which connect with each other and that adjust the pain message as it travels up the spinal cord

3. ...to the cerebral cortex, where the damage is assessed and then emotions and other bodily functions are adjusted accordingly; such as correcting the breathing of the sufferer.

4. This slower way creates duller, more constant pain. If the pain continues, the complete nervous system may be reprogrammed to build a lower threshold for pain.