Chronic pain is persistent pain, generally caused by a condition like fibromyalgia or arthritis. People with chronic pain need long-term treatment and therapy to manage their pain. They feel pain differently and process those pain messages differently from an acute, stub-your-toe or paper-cut pain because of their long experience with pain.
The chemicals released by the body when an injury occurs or when the body has other abnormal processes taking place actually make changes to the nervous system. The types of changes they make are related to the type of pain you feel. Normally, the central nervous system automatically inhibits unpleasant sensations like pain. But with chronic pain, the nervous system's function is altered and becomes more sensitive to pain. The nerve cells in people with chronic pain may become so sensitive that the brain perceives even a gentle touch as pain.
There is physical evidence, based on magnetic resonance imaging MRI scans, that shows an abnormal amount of stimulation in the brains of chronic pain patients, says Tongprasert. That means people with chronic pain physically perceive and feel pain differently — more intensely — than others.
When the brain is stimulated, the brain recognizes that pain stimulus, but also relies on past experiences to help determine what that stimulus is. When the brain has "memory" of chronic and persistent pain, it changes the way that it "feels" every new pain, and feels it more strongly.
In fact, nociceptors never develop in the brain; in embryos, the cells that are responsible for making nociceptors are different from the ones that make up the brain [Woolf ]. The brain is so insensitive to painful stimuli that neurosurgeons do not apply anaesthesia to the brain tissue they operate upon, allowing patients to be awake and completely responsive for the whole procedure. You can see this phenomenon for yourself in the video linked here.
Although nociceptors embedded in your sinuses are in the front of your face, the brain can still interpret sinus pain as coming from the middle of your head. One answer is that the brain mistakenly identifies pain as coming from the middle of your head.
Your brain can be bad at localizing certain types of head pain because there are so many different types of tissues in the head, and many of them are pretty bad at communicating where the hurt is happening. As another example, consider brain freeze, the painful headache you get for a few seconds after eating ice cream too quickly. Why does it happen? Think back to a cold day spent outside: when the cold air first hits the blood vessels on your face, they eventually widen, giving you ruddy cheeks.
The same thing happens when the top of your mouth is suddenly cooled - those blood vessels widen very suddenly, activating nociceptors in the roof of your mouth. You may have also heard of referred pain in the context of a heart attack - even though your heart is the damaged tissue, sufferers will often feel referred pain in their arm instead [Kosek ].
Finally, remember that your head is full of lots of tiny muscles. When these muscles are strained - say, because you were staring at your computer all day - the nociceptors embedded in these tissue types send pain signals. Many of these nociceptors are the type with a lot of branches, so that it can be hard for the brain to pinpoint exactly where the pain is coming from, and as a result the pain is difficult to localize.
Your brain also has the unfortunate ability to fabricate a sensation of pain when no nociceptors are active. Consider, for example, when you scrape your knee during a soccer game. This can go the other way, too - if you suffered from psychosomatic pain, you would feel pain even though your nociceptors are quiet.
Your brain can even create feelings of pain in places that have no nociceptors - like a hand that has been missing for years [Flor ].
Some scientists believe that migraines may be related to this kind of psychosomatic pain, but new evidence suggests that there is more to the story. Another theory is that migraines occur when an aberrant electrical activity in brain accidentally stimulates nociceptors in surrounding blood vessels.
Since this seems to affect areas of the cortex related to vision, the theory goes, this could explain why some migraine sufferers experience visual auras and dancing lights before the migraine starts.
This is known as referred pain and occurs because signals from different parts of the body often converge on the same neurones in the spinal cord. The gate control theory helps explain how the brain influences your experience of pain. It seems that several factors can affect how you interpret pain:.
This is the type of pain illustrated in the first diagram. Nociceptive pain is caused by any injury to body tissues, for example, a cut, burn or fracture broken bone.
Postoperative pain and cancer pain are other forms of nociceptive pain. This type of pain can be aching, sharp or throbbing. Nociceptive pain can be constant or intermittent and may be worsened by movement or by coughing, depending on the area it originates from. This is caused by abnormalities in the system that carries and interprets pain — the problem may be in the nerves, spinal cord or brain.
Neuropathic pain is felt as a burning, tingling, shooting or electric sensation. One form of neuropathic pain is associated with shingles — a skin condition caused by varicella zoster virus. The virus triggers inflammation of the nerves and this inflammation can set off a constant deep aching, tingling or burning sensation that in some people can persist for months after the shingles rash has resolved.
People with neuropathic pain may feel pain from stimuli that are not normally painful, such as light touch or cold. They can also be more sensitive than normal to stimuli that are usually painful. For example, bedclothes touching the affected area could feel painful, and a pin prick could feel excessively sharp. This type of pain is caused or worsened by psychological factors. Often the pain has a physical cause, but the degree of pain and disability are out of proportion to what would be experienced by most people with a similar disorder.
This does not mean that the pain is not real, even if a physical cause cannot be found. Any kind of pain can be complicated by psychological factors. This is short-lived pain warning the body that damage is occurring. It is a symptom of injury or disease at the tissue level, and tends to resolve as the injury or disease does. Chronic pain also called persistent pain can be caused by ongoing tissue damage, such as in osteoarthritis.
However, in some cases no physical cause for the pain can be found or pain persists long after the injury has healed. In many cases chronic pain is a disorder in itself rather than being the symptom of a disease process. Chronic pain can persist for months or even years after an initial injury and can be difficult to treat. People with chronic pain may experience sleeplessness, anxiety and depression, all of which can compound the problem. However, support and help are available, often in the form of a multidisciplinary approach, as carried out in pain management clinics.
Chronic pain is an area that is being researched intensively, with the hope of relieving this distressing condition in the future. Merck Manual Home Health Handbook. Overview of pain updated Aug Types of pain updated Aug Physiology and pathophysiology of pain revised September In: eTG complete.
Melbourne: Therapeutic Guidelines Limited; Nov. Types of pain revised February Skip to content. You prick your finger on something sharp. This causes tissue damage, which is registered by microscopic pain receptors nociceptors in your skin.
Each pain receptor forms one end of a nerve cell neurone.
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