About pain, pain conditions and pain relief

Pain occurs when the endings of special nerve fibers send signals to brain centers capable of generating the feeling of pain, or when some process within these nerve fbres make them send signals.

Many types of impacts can make these nerves send signals: Mechanicle pressure, chemical stimuli, elctric charges or electric current.

Mechanical pressure can occur by external impact, pressure from anatomical structures with som abnormality, musccular tension or tension in blood vessel walls.

Increased pressure in the tissue fluid due to osmosis or hindered fluid drainage can also make these nerves send pain signals.

Pain signals can also occur because of processes in the nerve fibres themselves, so called neuralgia.

An experience of pain pass several faces due to passing certain threshoulds of the stimuli and the way the stimuli are processed in the nerve system. A specific treshold can be reach immediately or the perseption can go though one or more thresholds before the definite threshold is reached:

- The stimulus is recognized, but not yet felt painful

- The stimulus result in the feeling of pain

- The pain gets unbearable. At this stage it is not possible to the individual to  let the stimulus stay on without retracting from the stimulus. And if the pain is not possible to avoid, it is not possible for the individual to concentrate on other things than the pain.

- The pain alleviates to a more tollerable point again due to automatic analgesic activities in the nerve system, for example secretion of endorphins.

The ultimate way to relieve pain is of cource curing the basic disease or injury that generates the pain. Sometimes this is not possible, one do not find any specific diosease or the healing takes time. Therefore it is often necessary to alleviate the pain itself or the physical factor creating the pain.

Analgesic drugs decrease or hinder the function of the nerves that create and propagate the nerve signals and thereby reduce pain.

The hinderance can be done at the nerve endings, at the propagation mechanism along the nerve fibre or at the connection between two nerve cells, the synapses.

Other drugs help by relieveing muscular tension or tension i blood vessel walls.

Still other drugs alleviate the process in the brain itself that makes the pain upon resceived pain signal.

Variants of pain and aspects of pain

The phenomenon of pain is something all of us have experienced in lesser or greater degree. We know the fact that pain is important for survival. A famous example is patients suffering from congenitial analgesia, ie the inability to feel pain. This is often associated with premature death, since no pain alerts about progressing damages to the body  caused by things like fractures, burns, or appendicitis. At the same time it is also clear that children with this disorder do not learn to avoid harmful stimuli. We also know that the most common reason for physician visits is pain. 50% of adults who visit a doctor do so because of the pain symptom. While pain is a serious personal problem, it is also a societal problem because of abcense from work, cocial costs and medical costs. Pain can occur in several variants and under several circumstances:

Subjective experience of pain

In many cases, one might ask how to describe pain. Pain is very much a personal experience. One person can not know how another feels the pain of for example his sprained foot, but he can imagine it based on personal experience from similar types of pain.

However, we can also think about the pain in two aspects: quality and intensity. The quality of pain may be described with the feelings we all have experienced: burning, stinging, burning, etc. 

The intensity of pain is a measure of the pain sensation, regardless of quality. Just how strong the pain you feel.

Emotional aspects of pain

At the same time, we can also say that pain is a subjective experience with the following characteristics; every pain has a certain strength or intensity. A needle felt definitely less intensive than a bone fracture. We can also say that pain has an emotional or emotional aspect, since pain is always associated with some discomfort. We also know that back pain evokes a process of thinking about the pain, and we can therefore add a cognitive aspect. Pain also has a spatial and temporal aspects, since we can feel more or less clear localization of the pain and more or less duration of pain.

Melzack and Torgerson's formulas of pain quality

Melzack and Torgerson (1971) established a form to describe the differnt quality aspects of pain. The formula uses three quality subaspects:  Sensorial qualities, emotional qualities, and evaluative qualities. The formula uses 102 words in small groups that describe different aspects of pain.

McGill Pain Questionnaire 

MPQ can  be used to measure the quality and intensity of pain and using this formula, the aspects of various pain syndromes can be compared. The most impressive with this form is that this form can be used for diagnosis, as it was perceived that people with the same disease often use the same words to describe pain. Various pain syndromes that can be uncovered using the McGill formulas are rheumatism, osteoarthritis, and phantom limb pain.

Subjective measures of pain intensity

McGill Pain Questionnaire have formulations to define the intensity of pain. How does one then measure the intensity (and not the quality) of pain? Here we have a few different ways.

One can use verbal report from the patient, visual analouge scales and numerical rating scales and these scales can be calibrated against experiments using different physical intensities of painful stimuli.

At NRS (numerical rating scale) pain can be given a score from 1 to 10, 10 is the very worst possible pain, and 1 is easily hurt. VAS (Visual analouge scale) is in many ways very similar to the NRS, but here one uses only one line of 10 cm without visible figures in which the patient must put a cross. In retrospect, use a ruler to read off the result.

Ojective measures of pain intensity

At the same time, recent research paved the way for new objective measures of pain, then one can not call the verbal report from a patient objectively. Examples of this are the EEG, fMRI and reflexes. EEG measures such as blood flow in the brain, and increased metabolism that particular can say something about the experience of pain.

Transient pain

It is most known for most of us are transient pain. It has a clear function in both humans and animals. First and foremost, it motivates us to pull us away from any harmful stimuli, but it will at the same time also teach us what stimuli that can be harmful. Transient pain may occur before serious damage occurs, and disappears after a few seconds. It is easy to imagine examples of this type of pain. An example is when you just put your hand on something hot, and pulls it away quickly..

Acute pain

If a sudden damage allready has occured pain is often the result. Acute pain will at first be extrema and then it will usually alleviate somewhat and continue as a more prolonged pain. If one makes movements or loads the injured body part in such a way that firther damage can occure, the sharp pain will suddenly reappear. It is due to this pain that we stay in peace to ease the healing process. This pain make us know that there will be a period when one has to stay calm and rest.

Most of us have probably experienced this also, whether you put your hand on a hot plate or sprain the heel.  For most of us it will not take more than 1-2 weeks before the damage is completely healed. But in some cases the pain continues even if it is a long time since the injury has healed. This is called chronic pain..

Chronic pain

The definition of chronic pain is pain that occurs in the absence of other diseases or remain long after the injury healed. Chronic pain affects quality of life. Statistics show that 28% of patients with chronic pain in western societies are also is diagnosed with depression. Additionally, 24% will have to give up their job as a direct result of the chronic pain.

Chronic pain is one of the fields within the pain that is researched most of the last century, since it has no apparent reason. In chronic pain, one can say that the pain no longer is a symptom of an injury or illness, but here is the pain a disorder in itself.

There is a tendency to diagnose chronic pain as a psychiatric disorder. Probably this attitude is faulty. Prabably there is some physical abnormality or unhealed  damage not so easily seen by examinations that trigger the nerves to send pain impulses to the brain.

Experimentally induced pain

In this case we are talking only about pain induced purposedly under controlled conditions to do research in order to study and explain the phenomenon of pain.

Factors that infuence the intensity of pain and the reaction to pain

Generally about psychological factors

The nerve system has machanism that boost the intensity of pain felt upon a stimulus and mechanisms that reduce the intensity. These mechanisms contain inhibitory nerve connections, exitory nerve connections and productions of endorphins that make an analgesic effect. These nervous mechanisms are to some extend controlled by psychological mechanisms. Therefore the psychological attitudes towards pain will directly infuence the intensity of the felt pain. These psychological mechanisms are influenced by the culture, by previous experiencees and also by conscious choises and conscious reasoning.

The role of endorphines

Endorphines are peptides that the thalamus, a part of the brain, and the pancreas gland produce when a person is subjected to paibful stimuli. The production of endorphines begin when the stimuli has worked some time. If a person decides to igore pain, the production of endorphines will often make the pain alleviate after some time. Chronic pain is often more or løes continually qaleviated by production of endorphines.

Thee ndorphines are resceived by receptor sites on the nerve cells that are leading pain impulses and they make the nerve cells reduce their firing of impulses and sendiing of impulses to the brain. They make a person or animal able to endure pain that it is not possible to withdraw from.

Endorphines are peptids, that is they consist of amino acids chained together. They have a chemical composition that resamble the composition of opiates, that is the effective subsatances in opium. The reason why opiates work is that they mimic endorphines.

Attention / distraction, and anxiety

Stimuli persceived at the same time as the painful stimulus, will lower the intensity of the pain. Also cognitive activities and strong mental concentration upon some taks have the ability to lower the pain felt. If for example a person is intenily preoccupied with reaching a specific goal, stimuli caused by his activities to reach those goals will not as likely cause pain or untollarable pain.

If we look at a nurse who puts vaccines or taking blood samples of children, we will see that he or she has a special technique. This method is based on the deflection of the patient from the painful stimuli that will inevitably follow. Distraction of attention may also explain why athletes ever to continue the race without checking that they are seriously injured.

A study on the effect of music and white noise in pain attenuation has shown that people quickly are able to use auditorial input to dampen the experience of pain. In an experiment (Melzack 1963b) was the subject hand in an ice bath, which produces a deep and severe pain, which most people fail more than a few minutes off. However, when the subject was able to listen to music and white noise, they would not just sit passively listening to music, but rather stepping to the beat, singing and change the volume of the music often to distraere attention on the pain.

However, the distraction does not work if you get a sudden increase in pain, only when we experience a gradual slow build-up of pain. This is that pain is "designed" to seize attention and react to it. We know in addition that if one is focusing on the pain it will in most cases be perceived as stronger. An experiment by Hall and Stride (1954) showed that if the word "pain" was the instruction to the person experimented on, then an electric shock would be perceived as more painful than if the word "pain" was omitted from the instructions.

The effect of previous experiences

Experimental research has shown that past experiences play a role in the perseption of pain and the reactions towards pain. Melzack and Scott (1957), raised Scottish terriers in isolated cages right from birth so they were completely unaffected by natural stimuli. This included that the dogs had never experienced bad incidences that would otherwise be inevitable for dogs.

When the dogs were fully adults, he conducted several experiments with surprising results. These dogs reacted very strangely to harmful stimuli. For example, many of them repeatedly appoached his nose and touched burning matches. Moreover, they also could take the spot of needles without showing any particular reaction to pain. On the other hand the dogs quite quickly learned to avoid harmful stimuli.

The conclusion is that young animals learn the basis of environment-based stimuli in childhood, and that this plays an important role in pain experience. Furthermore, it is also generally accepted that children are influenced by parents in their attitudes to pain. There are many different attitudes to pain, some are very influenced by a small cut, while others seem to not notice it once. It is clear that this can affect children's attitudes to pain, which will follow the rest of the life.

Cultural differences in the experience of pain

Research shows that cultural differences play a relatively large role in the experience of pain. For example, the rituals that in some cultures are performed completely normally will in other cultures be avoided because of the pain  they cause.

An example of this is trepanation which still takes place in Africa, where the scalp and underlying muscles are cut in order to arrive at the skull. This is done without anesthesia, and "patient" sitting quietly without showing signs of pain during the procedure. However, there is no evidence to suggest that humans are anatomically different in other cultures, and we find no differences in the free nerve endings or nerve paths. There are four different thresholds in relation to pain:

- Sans Threshold: the point where you detect stimuli
- Pain Threshold: the point where it feels painful stimuli.
- Pain tolerance: the point where the pain feels unbearable
- Extened pain tollerence due to demands from the society.


As previously mensioned there is no cultural variation in the sensory threshold, and sensory nerve fibers seems therefore to be the same at all. But there is definitely differences in pain threshold, as is shown by repeated experiment. For example, it has been shown in experimental research that North Europeans have a higher pain threshold for heat than native Mediterranean  inhabitants have.

The difference in pain treshold and the difference in the threshold of acceptance of pain is probably diferent in various cultures due to differences in psychological attitude.

In some cultures persons also are expected to endure pain so long that the production of endorphines in the body are increased, and then feeling of pain will decrease.

The significance of the situation

The situation in which a painful stimulus occur, have a significant effect upon the intensity of pain felt and the reaction to pain. This signifivance is to a great extend a result of the cultural upbringing of an individual and of previous experiences.

Pavlov (1927.1928) conducted an experiment that had great impact on the idea that the significance of the situation had an impact on pain experience. We know that dogs react with aggression upon the electric shock to their paws. However Pavlov found out that if he consistently presented the food to the dogs right in the wake of the shock, the dogs would not react aggressive. The dogs have thus created a new reaction to the shock, and the important in this context is that the stimulation will be located, identified and evaluated before it produced a conscious experience and outward behavior.

The importance of the situation can also appear with another example; Most people who experience to have pain in the stomach will conclude that there is only a stomach ache as a result of the gases. But in some cases, especially if one just for example, have learned about stomach cancer, this stomach ache feels totally convincing and more inclined toward cancer pain. The pain may persist on a specific high level in such cases until the person seeks medical assistance and verify that it's not stomach cancer. It is thus easy to see that the importance of the situation you're in plays a major role in the experience of pain, both for animals and humans.