The spinal cord is the main part of the body's central nervous system that conveys signals from the brain to the nerves throughout the body. Nerves coming from and leading to all parts of the body enter and exit the spinal cord along its entire length.
How Nerve Pain Occurs
There are 31 pairs of spinal nerves that exit the spinal cord through openings between the vertebrae. The point at which the nerve exits the spinal cord is called the nerve root, and where it branches out into many smaller nerves that control different parts of the body is called peripheral nerves. For example, a nerve that exits the lower back has peripheral branches that extend all the way down to the toes. Peripheral nerves comprise the peripheral nervous system.
The peripheral nerves include both motor nerves and sensory nerves:
- Sensory nerves are nerves that receive sensory stimuli, such as how something feels and if it is painful. They are made up of nerve fibers, called sensory fibers (mechanoreceptor fibers sense body movement and pressure placed against the body, and nociceptor fibers sense tissue injury).
- Motor nerves lead to the muscles and stimulate movement. They are made up of nerve fibers called motor fibers.
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Nerve Injury and Neuropathy Pain
While is has not been firmly established, it is thought that injury to any of the above types of nerve tissue can be a possible cause neuropathy pain.
The part of the nerve cell that is damaged by a neuropathy is the axon (the inner information pathway of the nerve cell) and/or its myelin covering (the fatty outer sheath that protects the nerve cell and assists in conveying information throughout the nervous system).
When neuropathy pain occurs by damage to the above structures, neuropathy is sustained by abnormal processing of sensory input by the peripheral nervous system and the central nervous system.