Symptom - Pain and the associative physical problems which begin to effect everyday life.

Pain is classed as a somatosensation, involving stimulation arising from cells in the body referred to as nociceptors. The function of pain is to alert the body to injury of some form, and in so doing to accelerate action towards dealing with the pain. The signal from which pain arises is most commonly tissue damage. As with many things exceptions can arise. An individual suffering with tissue damage may feel no pain, and individuals who appear to be suffering severe pain, show no signs of tissue damage. I will elaborate on this at a later point in this article.

Tissue damage can occur through cuts and bruises or by attack from bacteria, virus or fungus. It also occurs through ingesting or having chemical contact the skin. Heat also causes tissue damage, examples of this are sunburn and a direct flame. The injury causes the body to produce what is known as the acute inflammatory response. This response can last from a few hours to a few days.

Inflammation comprises of pain, thermal response, alongside redness and swelling. The body’s purpose in triggering these responses which unfortunately induce pain is to encourage blood flow to the area, a process referred to as vasodilation. The exchange of blood and fluids between blood vessels and body tissue increases, so that excess fluid, proteins and cell contents leak outwards while space is made for the invasion of extra fluid flow.

Blood vessels dilate and become permeable due to the presence of proteins called kinins. Kinins are highly potent in their ability to stimulate nociceptor (pain receptor)activity and induce pain response, it can activate release of a substance called arachidonic acid which subsequently promotes the release of prostaglandins.

Prostaglandins have a protective function, for example they block ulcer formation in the stomach, but in some cases they are powerful enough to increase inflammation further thus promoting pain. Clotting processes block lymphatic vessels and the areas surrounding the site of tissue damage are sealed (these are later visible as bruising), to prevent infection, by organisms such as bacteria.

The speed of inflammatory response, is dictated by the extent of tissue damage. The bacteria Staphylococcus aureus is highly toxic and response to it is quick, but streptoccal bacteria are less toxic, demanding a slower response, permitting it to overtake the body, occasionally can result in death.


The activity of pain receptors is very important and at this point I believe it necessary to expand upon its properties as relevant in the pain process. There are three types of pain receptor free nerve endings, each is adaptable to a particular required function. some respond to touch, others to pressure, temperature etc. Deviations from from what is considered normal fo rthe body, sets processes into action which casue these pain responses to be quickly modified.

During tissue damage, chemicals are released which can impact in one of three ways: they can directly effect pain receptor response, they make pain receptors more sensitive when faced with noxious stimuli and cause pain receptors to respond to current tissue damage, (where inflammation response has already occurred) by triggering pain in those areas at the slightest contact. If the contact is touch over a severe knock to the hand, the phenomenon is referred to as hyperalgesia, however if warm water runs over burnt skin it is called allodynia.

The presence in the tissue of chemicals such as potassium, histamine, bradykinin and serotonin will activate pain receptors, obviously heightening pain response, but prostaglandins, substance P, acetylcholine and adenosine triphosphate will effect the sensitivity of pain receptors so that they are triggered more quickly into creating a pain response.

Technology has through investigation postulated and tested evidence to show how help and management of pain situations is possible. A model was originally formulated by Patrick Wall and Ronald Melzack, which has lead to further development in more recent years something called the gate control theory of pain. In 1965, Wall and Melzack proposed that a 'gate' existed at the level of the spinal cord, which is able to modulate signals taken up by vessels going towards the spine from pain receptors at the site of tissue damage. The explanation of this theory is quite in depth and beyond the scope of this article at this time.However, it forms ther theory by which the Transcutaneous electrical nerve stimulation(TENS) is used as a means of reducing pain

The gate theory can also serve as evidence towards the phenomenon of arousal analgesia. This is where extreme emotion can work to switch off pain response in pain receptors. Substances such as those involved the fight or flight syndrome, have been observed as beign in abundance in the brain at these times.

Ofcourse it is not as simplistic an explanation as this, there are other factors involved, which play a part.

What can be seen from the evidence of gate control, arousal analgesia and drug intervention formulated to follow neural mechanisms, is that the pain sensing areas of the brain and neural system are extremely powerful and are capable along their length of organizing and reorganizing temporarily, until tissue has a chance to heal. An exception to this return to normality state, is in a scenario of limb amputation. Where neural pathways are severed, connecting cells higher along the path in the spinal cord die, and produce abnormalities in spinal circuitry. This is felt as pain in a limb which no longer exists and is referred to as phantom limb pain. This phenomenon stands as example of what is known as neuropathic pain. Neuropathic pain is defined as being “pain caused by abnormal patterns of activity in neurons rather than by actual tissue damage” . Neuropathic pain can be severe and is not easily treated, by conventional drug methods.

From information presented we gauge the importance of pain in notifying the body of tissue changes which can be injurious to health and well being, but that the tissue damage will not always induce a pain response and so there may be psychological issues involved with tissue damage and therefore pain. We achieve a degree of understanding of the pain receptor responses which promote pain and the body's natural means of inhibiting pain via the gate theory. We also are offered an insight in to the body's natural mechanism for combating pain response during periods of heightened arousal via the presence of fight or flight substances.

This has obviously been a lengthy explanation, but if you are in pain, sometimes knowing why the pain exists in you is a way of coming to deal with its maintenance and possible elimination.