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 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
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
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