Pain appears; pain appears. What is pain, types and causes of pain

In the entire history of mankind, only 20 cases have been described in which people had absolutely no pain sensitivity. This phenomenon is called analgia. People suffering from this genetic disorder receive a large number of injuries; in early childhood they develop multiple scars on the tongue and mucous membranes of the mouth: when teething, the baby begins to bite his tongue and cheeks. Later fractures and burns appear. It is very difficult for such people to live and they have to regularly examine their body for damage. That is, pain is actually a useful phenomenon, it allows a person to understand: harmful processes are going on in the body, you need to find out what is wrong, or, if the pain is sharp, you need to quickly change behavior (for example, remove your hand from the hot iron).

What causes pain

The nature of pain is not always the same. In the simplest case, if pain sensitivity is normal, pain occurs as a result of infection, metabolic disorder, or injury. Tissue damage activates pain receptors, which transmit a signal to the brain. Such pain - also called physiological - easily goes away after eliminating its cause and treating with painkillers. It happens that a diseased organ cannot be cured quickly and completely, and then treating pain becomes an independent task.

Another cause of pain is damage to the nervous system itself. This pain is called neuropathic. Damage can affect individual nerves and areas of the brain or spinal cord. This is the pain of herpes, and toothache, and known to tennis players and people working at the keyboard, carpal tunnel syndrome. Neuropathic pain is often associated with sensory abnormalities. It happens that the most common stimuli (heat, cold, touch) are perceived as painful. This phenomenon is called allodynia. Hyperalgesia is an increased pain response to a weak painful stimulus.

The perception of pain depends on many factors. For example, on gender (on average, women are more sensitive to pain) and religiosity (religious people find it easier to cope with pain than atheists).

Phantom pain

As early as 1552, the French surgeon Ambroise Pare described the complaints of wounded people about pain in amputated limbs. Today such pains are called phantom pains. It has been established that all people who have had an arm or leg removed and half of the women who have had breast amputation complain of phantom pain. One year after surgery, only two thirds of patients experience pain.

It cannot be said that the causes of phantom pain are known. It is now believed that in different parts of the central nervous system a system of foci is formed that generate pathological pain impulses.
There are more than 40 treatments for phantom pain, but only 15% of patients are completely cured. Since the specific part of the nervous system responsible for the appearance of phantom pain has not been identified, surgical methods treatments are ineffective. Local administration of painkillers helps only a few patients. The technique of electrical stimulation of the motor cortex of the brain is considered quite effective. It can be carried out without surgical intervention- on the surface of the head - or by implanting an electrode for constant direct stimulation of areas of the cortex.

Hangover pain

One of the actions ethyl alcohol- suppression of the production of the pituitary hormone, which is responsible for fluid retention in the body. With a deficiency of this hormone, excessive secretion of water by the kidneys begins and dehydration occurs. Alcohol also stimulates the production of insulin, which helps the tissues take up glucose. When drinking liqueurs and sweet wines, insulin synthesis is doubled. As a result, blood sugar levels drop, which can also cause headache. It can also be provoked by impurities, which are especially abundant in dark-colored drinks: red wine, cognac, whiskey.

The World Health Organization recommends treating cancer pain according to the pain ladder. First step of the ladder - mild pain, for the treatment of which non-steroidal anti-inflammatory drugs are used. When first-stage medications stop helping, in Russia they use the weak opioid analgesic tramadol, which is not a narcotic. At the third stage, for severe unbearable pain, narcotic analgesics are used.
Using narcotic drugs You may experience weakness, which usually goes away after a few days. Constipation may occur because opioids suppress intestinal motility. Over time, the dose of analgesic prescribed by the doctor ceases to help. This happens because the pain has gotten worse or because resistance to the drug has developed. In this case, the doctor will recommend increasing the dose of the medication or prescribing another analgesic. Developing resistance does not mean becoming dependent on the drug. Opioid analgesics, when prescribed for the treatment of pain and used correctly, do not cause psychological dependence.

An opioid overdose can cause breathing problems, so increasing the dose of the medication is only possible under the supervision of a doctor. Stopping opioids abruptly is also dangerous, but with the help of a doctor, you can gradually reduce the dose of the drug and avoid unpleasant symptoms.

Pain not caused by injury

The American Journal of Cardiology in 1989 published data from a survey of more than seven thousand patients with pain in the heart who were admitted to the department emergency care. According to the results of the examination, only 4% of patients suffered from myocardial infarction, in half one could suspect a heart attack, and 40% of the people who applied had a completely healthy heart. Many parents have had to deal with a situation where a child, cheerful and active on weekends, collapses on Monday before school and complains of abdominal pain. And this is not pretense: the stomach really hurts, and yet everything is in order with the stomach and other organs.

Headache, pain in the heart, stomach, back, which arose without organic damage tissues and nerves is called psychogenic. The cause of psychogenic pain is psychological trauma, depression and intense emotional states: grief, anger, resentment. Anxious and suspicious people, as well as people prone to demonstrative behavior, are most susceptible to psychogenic pain.

In this condition, the functioning of the nervous system and its sensitivity change: impulses that are usually not perceived as painful begin to be interpreted as such.

Despite the fact that psychogenic pain is not caused by a malfunction of the organs, it must be taken seriously. Firstly, it is important to make sure that this is psychogenic pain and not a dangerous disease. Secondly, psychogenic pain, like any other, worsens the quality of life. You need to cope with this condition with the help of psychotherapy.

How to understand that a person is in pain

There are times when a sick person cannot tell his loved ones that he is in pain. But for those caring for him, it is important to determine the appearance and severity of pain. Often such problems arise when caring for small children, frail patients, or people who do not speak due to severe depression.

A sign that a person is in pain may be crying, groaning, or a grimace of suffering on the face. But these signs are not always reliable. If we are talking about long-term chronic pain, then there may be no tears or grimaces of suffering. In this case, you need to pay attention to changes in behavior: the sick person either freezes in a forced position, in which pain is felt the least, or, conversely, rushes around to find the most comfortable position. He avoids movements that could cause pain. It happens that a person suddenly becomes apathetic and loses interest in the environment. This is also a likely signal that he is in pain. Doctors can use graphic scales to assess pain: compare different behavioral characteristics, physiological manifestations and in accordance with accepted standards determine how severe the patient's pain is. To do this, for example, it is necessary to perform a test with an analgesic, paying attention to the respiratory rate, pulse, blood pressure and general behavior of the person.

Pain represents an opportunity for the body to communicate to the subject that something bad has happened. Pain draws our attention to burns, fractures, sprains and advises us to be careful. There are a small number of people who are born without the ability to feel pain, they can endure the most severe injuries. As a rule, they die in early period maturity. Their joints wear out from excessive load, since without feeling discomfort from staying in the same position for a long time; they do not change their body position for a long time. No pain symptoms infectious diseases, undetected in time, and various injuries to parts of the body occur in a more acute form. But there are significantly more people who feel chronic pain (constant or periodic pain in the back, head, arthritis, cancer).

Nociceptive sensitivity(from Lat. notion - I cut, I damage) - a form of sensitivity that allows the body to recognize influences that are harmful to it. Nociceptive sensitivity can be subjectively presented in the form of pain, as well as in the form of various interoreceptive sensations, such as heartburn, nausea, dizziness, itching, numbness.

Painful sensations arise as a response of the body to such influences that can lead to a violation of its integrity. Characterized by pronounced negative emotional coloring and vegetative changes (increased heart rate, dilated pupils). In relation to pain sensitivity sensory adaptation practically absent.

Pain sensitivity determined by pain thresholds, among which are:

The lower one, which is represented by the magnitude of irritation at the first appearance sensations of pain,

The upper one, which is represented by the magnitude of irritation at which pain becomes unbearable.

Pain thresholds vary depending on general condition organism and from cultural stereotypes. Thus, women are more sensitive to pain during periods during ovulation. In addition, they are more sensitive to electrical stimulation than men, but have the same sensitivity to extreme thermal stimulation. Representatives of traditional ethnic groups are more resistant to pain.

Unlike vision, for example, pain is not localized to any specific nerve fiber that connects the receptor to the corresponding part of the cerebral cortex. There is also no single type of stimulus that causes pain (like, say, light irritates vision), and there are no special pain receptors (like the rods and cones of the retina). Stimuli that cause pain, in small doses, can also cause other sensations, such as a feeling of warmth, cold, smoothness or roughness.

Theories of pain. There were two alternative positions in the interpretation of the specificity of pain reception. One position was formed by R. Descartes, who believed that there are specific pathways coming from specific pain receptors. The more intense the flow of impulses, the stronger the pain. Another position was presented, for example, by Goldscheider (1894), who denied the existence of both specific pain receptors and specific pathways pain conduction. Pain occurs whenever the brain receives too much stimulus from other modalities (cutaneous, auditory, etc.). It is currently believed that there are still specific pain receptors. Thus, in Frey's experiments it was proven that on the surface of the skin there are special pain points, stimulation of which does not cause any sensations other than pain. These pain points are more numerous than pressure or temperature tender points. In addition, the skin can be made insensitive to pain using morphine, but other types of skin sensitivity are not affected. Free nerve endings, also located in the internal organs.

Pain signals are transmitted through spinal cord to the nuclei of the thalamus and then to the new cortex and limbic system. Along with the nonspecific mechanisms of pain, which are activated when any afferent nerve conductors are damaged, there is a special nervous apparatus for pain sensitivity with special chemoreceptors that are irritated by kinins formed during the interaction of blood proteins with damaged tissues. Kinins can be blocked by painkillers (aspirin, pyramidon).

It’s interesting how painful sensations are remembered. Experiments show that after medical procedures, people forget about the duration of pain. Instead, the moments of the strongest and final pain sensations are recorded in memory. D. Kahneman and his colleagues established this when they asked participants to put one hand in ice water that caused pain and hold it in it for 60 seconds, and then the other in the same water for 60 seconds, plus another 30 seconds, but During these 30 seconds the water no longer caused such severe pain. And when the experiment participants were asked which procedure they would like to repeat, the majority wanted to repeat a longer procedure, when the pain, although it lasted longer, subsided at the end of the procedure. When patients recalled the pain experienced during a rectal examination a month later, they also better remembered the last (as well as the most painful) moments, rather than the total duration of the pain. This leads to the conclusion that it is better to slowly ease the pain during a painful procedure than to abruptly end the procedure at the most painful moment. In one experiment, a doctor did this during a rectal examination procedure - he extended the procedure by one minute and made sure that during this time the patient’s pain decreased. And although an additional minute of discomfort did not reduce the total duration of pain during the procedure, patients later recalled this procedure as less painful than one that lasted less time but ended at the most painful moment.

Types of pain. It has long been noted that consciously inflicting additional pain on oneself helps reduce the subjective strength of pain. For example, Napoleon, who suffered from kidney stones, interrupted this pain by burning his hand in the flame of a candle. This raises the question of what should perhaps be said about different types of pain.

It has been found that there are two types of pain:

Pain, transmitted by large-diameter fast-conducting nerve fibers (L-fibers), is sharp, distinct, fast-acting, and appears to originate from specific areas of the body. This warning system body, indicating that it is urgent to remove the source of pain. This type of pain can be felt if you prick yourself with a needle. The warning pain quickly disappears.

The second type of pain is also transmitted by slowly conducting nerve fibers (S-fibers) of small diameter. It's slow, aching, Blunt pain, which is different widespread and very unpleasant. This pain intensifies if the irritation is repeated. It is a pain resembling system it signals to the brain that the body has been damaged and movement must be restricted.

Although there is no generally accepted theory of pain control gate theory (or sensory gating), created by psychologist R. Melzack and biologist P. Wall (1965, 1983), is considered as the most substantiated. In accordance with it, it is believed that the spinal cord has a kind of nerve “gate” that either blocks pain signals or gives them the opportunity (relief) to go to the brain. They noticed that one type of pain sometimes suppresses another. Hence the hypothesis was born that pain signals from different nerve fibers pass through the same nerve “gates” in the spinal cord. If the gate is “closed” by one pain signal, other signals cannot pass through it. But how are the gates closed? Signals transmitted by large, fast-acting nerve fibers of the warning system appear to close the spinal pain gate directly. This prevents the slow pain "reminder system" from reaching the brain.

Thus, if tissue is damaged, small fibers are activated, opening the neural gates, and pain is felt. Activation of large fibers causes the pain gate to close, causing pain to subside.

R. Melzack and P. Wall believe that the gate control theory explains the analgesic effects of acupuncture. Clinics use this effect by applying a weak electricity: such stimulation, felt only as slight tingling, can significantly reduce more excruciating pain.

In addition, pain can be blocked at the level of the spinal hilum due to an increase in general arousal and the appearance of emotions, including during stress. These cortical processes activate fast L-fibers and thereby block access for the transmission of information from S-fibers.

Also, the gate to pain can be closed with the help of information that comes from the brain. Signals that travel from the brain to the spinal cord help explain examples of psychological effects on pain. If you divert attention from pain signals in various ways, the sensation of pain will be significantly less. Injuries sustained in sports games, may not be noticed until you shower after the game. While playing basketball in 1989, Ohio State University player J. Burson broke his neck, but continued to play.

This theory also helps explain the occurrence of phantom pain. Just as we see a dream with our eyes closed or hear a ringing in complete silence, 7 out of 10 amputees have pain in their amputated limbs (in addition, it may seem to them that they are moving). This phantom limb sensation suggests that (as in the examples with vision and hearing) the brain may misunderstand the spontaneous activity of the central nervous system that occurs in the absence of normal sensory stimulation. This is explained by the fact that after amputation, partial regeneration of nerve fibers occurs, but primarily of the S-fiber type, but not of the L-fiber. Because of this, the spinal gate always remains open, which leads to phantom pain.

Pain control. One way to relieve chronic pain is to stimulate (massage, electromassage or even acupuncture) large nerve fibers so that they close the path to pain signals. If you rub the skin around the bruise, you create additional irritation, which will block some of the pain signals. Ice on the bruised area not only reduces swelling, but also sends cold signals to the brain that close the pain gate. Some people with arthritis may wear a small, portable electrical stimulator near the affected area. When it irritates the nerves in a sore spot, the patient feels vibration rather than pain.

Depending on the symptoms in a clinical setting, one or more methods of pain relief are chosen: medications, surgery, acupuncture, electrical stimulation, massage, gymnastics, hypnosis, auto-training. Thus, the widely known preparation according to the Lamaze method (preparation for childbirth) includes several of the above-mentioned techniques. Among them is relaxation ( deep breathing and muscle relaxation), counterstimulation (light massage), distraction (concentrating attention on some pleasant object). After E. Worthington (1983) and his colleagues conducted several such sessions with women, the latter more easily tolerated the unpleasant sensations associated with holding their hands in ice water. Nurse may distract patients who are afraid of needles by speaking kindly and asking them to look somewhere while inserting a needle into the body. Beautiful view looking at a park or garden from a hospital ward window also has a positive effect on patients, helping them to forget unpleasant feelings. When R. Ulrich (1984) became familiar with medical records patients at the Pennsylvania Hospital, he concluded that patients who were treated in rooms overlooking the park required less medication and left the hospital faster than those who lived in cramped rooms whose windows faced a blank brick wall.

Neuropathic pain, unlike ordinary pain, which is a signaling function of the body, is not associated with dysfunction of any organ. This pathology becomes in Lately an increasingly common illness: according to statistics, 7 out of 100 people suffer from neuropathic pain of varying degrees of severity. This type of pain can make doing the simplest activities excruciating.

Kinds

Neuropathic pain, like “ordinary” pain, can be acute or chronic.

There are also other forms of pain:

Moderate neuropathic pain in the form of burning and tingling. Most often felt in the extremities. It does not cause any particular concern, but it creates psychological discomfort in a person.
Pressing neuropathic pain in the legs. It is felt mainly in the feet and legs, and can be quite pronounced. Such pain makes walking difficult and brings serious inconvenience to a person’s life.
Short-term pain. It may last only a couple of seconds and then disappears or moves to another part of the body. Most likely caused by spasmodic phenomena in the nerves.
Excessive sensitivity when the skin is exposed to temperature and mechanical factors. The patient experiences discomfort from any contact. Patients with this disorder wear the same familiar things and try not to change positions during sleep, since changing positions interrupts their sleep.

Causes of neuropathic pain

Neuropathic pain can occur due to damage to any part of the nervous system (central, peripheral and sympathetic).

We list the main influencing factors for this pathology:

Diabetes. This metabolic disease can cause nerve damage. This pathology is called diabetic polyneuropathy. It can lead to neuropathic pain of various nature, mainly localized in the feet. Pain syndromes intensify at night or when wearing shoes.
Herpes. The consequence of this virus may be postherpetic neuralgia. More often this reaction occurs in older people. Neuropathic post-herpes pain can last for about 3 months and is accompanied by severe burning in the area where the rash was present. There may also be pain from touching clothing and bedding to the skin. The disease disrupts sleep and causes increased nervous excitability.
Spinal cord injury. Its consequences cause long-term pain symptoms. This is due to damage to the nerve fibers located in the spinal cord. This can be severe stabbing, burning and spasmodic pain in all parts of the body.
This serious brain injury causes great damage to the entire human nervous system. A patient who has undergone this disease, for a long time (from a month to a year and a half) may feel painful symptoms of a stabbing and burning nature in the affected side of the body. Such sensations are especially pronounced when in contact with cool or warm objects. Sometimes there is a feeling of freezing of the limbs.
Surgical operations. After surgical interventions caused by the treatment of diseases of internal organs, some patients are bothered by discomfort in the suture area. This is due to damage to peripheral nerve endings in the surgical area. Often such pain occurs due to removal of the mammary gland in women.
This nerve is responsible for facial sensitivity. When it is compressed as a result of injury and due to the expansion of a nearby blood vessel, intense pain can occur. It can occur when talking, chewing, or touching the skin in any way. More common in older people.
Osteochondrosis and other diseases of the spine. Compression and displacement of the vertebrae can lead to pinched nerves and the appearance of pain of a neuropathic nature. Squeezing spinal nerves leads to the emergence radicular syndrome, in which pain can manifest itself in completely different parts of the body - in the neck, in the limbs, in the lumbar region, as well as in the internal organs - in the heart and stomach.
Multiple sclerosis. This damage to the nervous system can also cause neuropathic pain in different parts bodies.
Radiation and chemical exposure. Radiation and chemicals have Negative influence on neurons of the central and peripheral nervous system, which can also be expressed in the occurrence of pain of a different nature and varying intensity.

Clinical picture and diagnosis of neuropathic pain

Neuropathic pain is characterized by a combination of specific sensory disturbances. The most characteristic clinical manifestation neuropathy is a phenomenon called medical practice"allodynia".

Allodynia is a manifestation of a pain reaction in response to a stimulus that healthy person does not cause pain.

A neuropathic patient can experience severe pain from the slightest touch and literally from a breath of air.

Allodynia can be:

mechanical, when pain occurs when pressure is applied to certain areas skin or irritation with their fingertips;
thermal, when pain manifests itself in response to a temperature stimulus.

There are no specific methods for diagnosing pain (which is a subjective phenomenon). However, there are standard diagnostic tests that allow you to evaluate symptoms and, based on them, develop a therapeutic strategy.

Serious assistance in diagnosing this pathology will be provided by the use of questionnaires to verify pain and its quantitative assessment. It will be very useful accurate diagnosis causes of neuropathic pain and identification of the disease that led to it.

To diagnose neuropathic pain in medical practice, the so-called method of three“S” - look, listen, correlate.

look - i.e. identify and evaluate local violations pain sensitivity;
listen carefully to what the patient says and note characteristic features in their description of pain symptoms;
correlate the patient’s complaints with the results of an objective examination;

It is these methods that make it possible to identify symptoms of neuropathic pain in adults.

Neuropathic pain - treatment

Treatment of neuropathic pain is often a lengthy process and requires a comprehensive approach. The therapy uses psychotherapeutic, physiotherapeutic and medicinal methods.

Medication

This is the main technique in the treatment of neuropathic pain. Often, such pain cannot be relieved with conventional painkillers.

This is due to the specific nature of neuropathic pain.

Treatment with opiates, although quite effective, leads to tolerance to the drugs and can contribute to the development of drug addiction in the patient.

Most often used in modern medicine lidocaine(in the form of ointment or patch). The drug is also used gabapentin And pregabalin- effective medicines produced abroad. Together with these means they use - sedatives for the nervous system, reducing its hypersensitivity.

In addition, the patient may be prescribed drugs that eliminate the consequences of the diseases that led to neuropathy.

Non-drug

In the treatment of neuropathic pain important role plays physiotherapy. IN acute phase diseases use physical methods to relieve or reduce pain syndromes. Such methods improve blood circulation and reduce spasmodic phenomena in the muscles.

At the first stage of treatment, diadynamic currents, magnetic therapy, and acupuncture are used. In the future, physiotherapy is used that improves cellular and tissue nutrition - laser, massage, light and kinesitherapy (therapeutic movement).

During the recovery period physical therapy is given great importance. Also used various techniques relaxations that help eliminate pain.

Treatment of neuropathic pain folk remedies not particularly popular. Patients are strictly prohibited from using traditional methods of self-medication (especially heating procedures), since neuropathic pain is most often caused by inflammation of the nerve, and its heating is fraught with serious damage, including complete death.

Acceptable phytotherapy(treatment with herbal decoctions), however, before using any herbal remedy, you should consult your doctor.

Neuropathic pain, like any other, requires careful attention. Timely treatment will help avoid severe attacks of the disease and prevent its unpleasant consequences.

The video will help you understand the problem of neuropathic pain in more detail:

What do you know about pain and painful sensations? Do you know how the perfect pain mechanism works?

How does pain occur?

Pain, for many, is a complex experience consisting of a physiological and psychological response to a noxious stimulus. Pain is a warning mechanism that protects the body by influencing it to withdraw from harmful stimuli. It is primarily associated with injury or threat of injury.

Pain is subjective and difficult to quantify because it has both an emotional and sensory component. Although the neuroanatomical basis for the sensation of pain develops before birth, individual pain responses develop in early childhood and are, in particular, influenced by social, cultural, psychological, cognitive and genetic factors. These factors explain differences in pain tolerance among people. For example, athletes may resist or ignore pain while playing sports, and some religious practices may require participants to endure pain that seems unbearable to most people.

Pain sensations and pain function

An important function of pain is to warn the body of possible damage. This is achieved through nociception, the neural processing of noxious stimuli. Painful sensation, however, is only one part of the nociceptive response, which may include an increase blood pressure, increased heart rate and reflexive avoidance of a noxious stimulus. Acute pain may result from breaking a bone or touching a hot surface.

During acute pain, an immediate intense sensation of short duration, sometimes described as a sharp, startling sensation, is accompanied by a dull throbbing sensation. Chronic pain, which is often associated with diseases such as cancer or arthritis, is more difficult to find and treat. If the pain cannot be relieved, psychological factors, such as depression and anxiety, can worsen the condition.

Early concepts of pain

The concept of pain is that pain is a physiological and psychological element of human existence and thus it has been known to mankind since the earliest eras, but the ways in which people react and understand pain vary greatly. In some ancient cultures, for example, pain was deliberately inflicted on people as a means of appeasing angry gods. Pain was also seen as a form of punishment, inflicted on people gods or demons. In ancient China, pain was considered to be the cause of an imbalance between the two complementary forces of life, yin and yang. The ancient Greek physician Hippocrates believed that pain was associated with too much or too little of one of the four spirits (blood, phlegm, yellow bile or black bile). The Muslim physician Avicenna believed that pain is a sensation that arose with a change in the physical state of the body.

Mechanism of pain

How does the pain mechanism work, where does it turn on and why does it go away?

Theories of pain
Medical understanding of the mechanism of pain and the physiological basis of pain is a relatively recent development, beginning in earnest in the 19th century. At that time, various British, German and French doctors recognized the problem of chronic "pain without lesions" and explained them functional disorder or constant irritation of the nervous system. Another of the creative etiologies proposed for pain was the German physiologist and anatomist Johannes Peter Müller's "Gemeingefühl", or "cenesthesis", the human ability to correctly perceive internal sensations.

American physician and author S. Weir Mitchell studied the mechanism of pain and observed soldiers civil war suffering from causalgia (constant burning pain, later called complex regional pain syndrome), phantom pain of limbs and others painful conditions after their initial wounds had healed. Despite the strange and often hostile behavior of his patients, Mitchell was convinced of the reality of his physical suffering.

By the late 1800s, the development of specific diagnostic tests and the identification of specific signs of pain began to redefine the practice of neurology, leaving little room for chronic pain that could not be explained in the absence of other physiological symptoms. At the same time, practitioners of psychiatry and the emerging field of psychoanalysis discovered that "hysterical" pain offered potential insight into mental and emotional states. Contributions from individuals such as the English physiologist Sir Charles Scott Sherrington supported the concept of specificity, according to which "real" pain was a direct individual response to a specific noxious stimulus. Sherrington coined the term "nociception" to describe the response of pain to such stimuli. Specificity theory suggested that people who reported pain in the absence of an obvious cause were delusional, neurotically obsessive, or malingering (often a finding of military surgeons or those who handled workers' compensation cases). Another theory that was popular among psychologists at the time but was soon abandoned was the intensity theory of pain, in which pain was considered an emotional state caused by unusually intense stimuli.

In the 1890s, German neurologist Alfred Goldscheider, who was studying the mechanism of pain, endorsed Sherrington's insistence that the central nervous system integrates input from the periphery. Goldscheider proposed that pain results from the brain's recognition of spatial and temporal patterns of sensation. French surgeon René Lerich, who worked with casualties during World War I, theorized that nerve injury that damages the myelin sheath surrounding sympathetic nerves(nerves involved in the response) can lead to sensations of pain in response to normal stimuli and intrinsic physiological activity. American neurologist William C. Livingston, who worked with patients with work-related injuries in the 1930s, charted feedback in the nervous system, which he called a “vicious circle.” Livingston proposed that severe, long-term pain causes functional and organic changes in the nervous system, thereby creating a chronic pain condition.

However, various theories of pain have been to a large extent ignored until World War II, when organized groups of doctors began to observe and treat large numbers of people with similar injuries. In the 1950s, American anesthesiologist Henry C. Beecher, using his experience with civilian patients and wartime casualties, found that soldiers with severe wounds often fared much worse than civilian surgical patients. Beecher concluded that pain was the result of fusion physical sensations with a cognitive and emotional “reactionary component”. Thus, the mental context of pain is important. Pain for a surgical patient meant disruption of normal life and fear of serious illness, while pain for wounded soldiers meant release from the battlefield and an increased chance of survival. Therefore, the assumptions of specificity theory based on laboratory experiments, in which the reaction component was relatively neutral, could not be applied to the understanding of clinical pain. Beecher's findings were supported by the work of American anesthesiologist John Bonica, who in his book The Management of Pain (1953) believed that clinical pain included both physiological and psychological components.

Dutch neurosurgeon Willem Nordenbos expanded the theory of pain as the integration of multiple inputs to the nervous system in his short but classic book Pain (1959). Nordenbos' ideas appealed to Canadian psychologist Ronald Melzack and British neurologist Patrick David Wall. Melzack and Stena combined the ideas of Goldscheider, Livingston and Nordenbos with available research data, and in 1965 they proposed the so-called pain theory of pain management. According to gate control theory, the perception of pain depends on nervous mechanism in the substantial gelatinous layer of the dorsal horn of the spinal cord. The mechanism acts as a synaptic gate that modulates the sensation of pain from myelinated and unmyelinated peripheral nerve fibers and the activity of inhibitory neurons. Thus, stimulating nearby nerve endings can inhibit nerve fibers that transmit pain signals, which explains the relief that can occur when the injured area is stimulated by pressure or friction. Although the theory itself turned out to be incorrect, it was implied that laboratory and clinical observations taken together could demonstrate a physiological basis complex mechanism neural integration for pain perception, inspiring and challenging a younger generation of researchers.

In 1973, building on the surge of interest in pain caused by Walls and Melzack, Bonica organized a meeting between interdisciplinary pain researchers and clinicians. Under Bonica's leadership, the conference, which took place in the United States, gave birth to an interdisciplinary organization known as the International Association for the Study of Pain (IASP) and a new journal called Pain, originally edited by Wall. The formation of the IASP and the launch of the journal marked the emergence of pain science as a professional field.

In subsequent decades, pain research has expanded significantly. Two important conclusions emerged from this work. First, it has been found that severe pain from injury or other stimulus, if continued over a period of time, alters the neurosurgery of the central nervous system, thereby sensitizing it and leading to neuronal changes that are carried out after the original stimulus is removed. This process is perceived as chronic pain for the affected person. Many studies have demonstrated the involvement of neuronal changes in the central nervous system in the development of chronic pain. In 1989, for example, American anesthesiologist Gary J. Bennett and Chinese scientist Xie Yikuan demonstrated the neural mechanism underlying this phenomenon in rats with constrictive ligatures placed loosely around the sciatic nerve. In 2002, Chinese neurologist Min Zhuo and colleagues reported the identification of two enzymes, adenylyl cyclase type 1 and 8, in mouse forebrains that play an important role in sensitizing the central nervous system to painful stimuli.

The second finding that emerged was that pain perception and response differed by gender and ethnicity, as well as by training and experience. Women appear to suffer pain more often and with more emotional distress than men, but some evidence suggests that women can cope with severe pain more effectively than men. African Americans demonstrate higher vulnerability to chronic pain and more high level disabilities than white patients. These observations are confirmed by neurochemical studies. For example, in 1996, a group of researchers led by American neuroscientist John Levine reported that Various types Opioid medications provide different levels of pain relief in women and men. Other animal studies have suggested that pain in early age may cause neuronal changes to molecular level, which influence a person's pain response as an adult. A significant finding from these studies is that no two patients experience pain in the same way.

Physiology of pain

Although subjective, most pain is related to tissue damage and has a physiological basis. However, not all tissues are susceptible to the same type of injury. For example, although skin is sensitive to burning and cutting, visceral organs can be cut without causing pain. However, excessive stretching or chemical irritation of the visceral surface will cause pain. Some tissues do not cause pain no matter how they are stimulated; the liver and alveoli of the lungs are insensitive to almost every stimulus. Thus, tissues respond only to specific stimuli that they may encounter and are generally impervious to all types of damage.

Mechanism of pain

Pain receptors, located in the skin and other tissues, are nerve fibers with endings that can be excited by three types of stimuli - mechanical, thermal and chemical; some endings respond primarily to one type of stimulation, whereas other endings can detect all types. Chemicals produced by the body that stimulate pain receptors include bradykinin, serotonin and histamine. Prostaglandins are fatty acids that are released during inflammation and can increase the sensation of pain by sensitizing nerve endings; that increased sensitivity is called hyperalgesia.

The biphasic experience of acute pain is mediated by two types of primary afferent nerve fibers that transmit electrical impulses from tissues to the spinal cord through ascending nerve pathways. Delta A fibers are the larger and more rapidly conducting of the two types due to their thin myelin coating, and are therefore associated with sharp, well-localized pain that first occurs. Delta fibers are activated by mechanical and thermal stimuli. Smaller, unmyelinated C fibers respond to chemical, mechanical, and thermal stimuli and are associated with a lingering, poorly localized sensation that follows the first rapid sensation of pain.

Pain impulses penetrate the spinal cord, where they synapse mainly on dorsal horn neurons in the marginal zone and substantial gelatinoses gray matter spinal cord. This area is responsible for regulating and modulating incoming impulses. Two different pathways, the spinothalamic and spinoreticular tracts, carry impulses to the brain and thalamus. The spinothalamic input is thought to influence the conscious experience of pain, and the spinoreticular tract is thought to produce the arousal and emotional aspects of pain.

Pain signals can be selectively inhibited in the spinal cord through a descending pathway that originates in the midbrain and ends in the dorsal horn. This analgesic (pain-relieving) response is controlled by neurochemicals called endorphins, which are opioid peptides such as enkephalins that are produced by the body. These substances block the reception of painful stimuli by binding to neural receptors that activate the painkiller neural pathway. This system can be activated by stress or shock and is likely responsible for the absence of pain associated with severe trauma. This may also explain people's different abilities to perceive pain.

The origin of pain signals may be unclear to the sufferer. Pain that originates from deep tissues but is “felt” in superficial tissues is called pain. Although the exact mechanism is unclear, this phenomenon may result from the convergence of nerve fibers from different tissues onto the same part of the spinal cord, which may allow nerve impulses from one pathway to travel to other pathways. Phantom limb pain is an amputee who experiences pain in her missing limb. This phenomenon occurs because the nerve trunks that connect the now missing limb to the brain still exist and are capable of firing. The brain continues to interpret stimuli from these fibers as coming from what it previously learned was a limb.

Psychology of pain

The perception of pain arises from the brain processing new sensory input with existing memories and emotions, just like other perceptions. Childhood experiences, cultural attitudes, heredity and gender are factors that contribute to each individual's development of perception and response to different types of pain. Although some people can physiologically withstand pain better than others, cultural factors, rather than heredity, usually explain this ability.

The point at which a stimulus begins to become painful is the pain threshold; Most studies have found that views are relatively similar among disparate groups of people. However, the pain tolerance threshold, the point at which pain becomes unbearable, varies significantly among these groups. A stoic, unemotional response to trauma may be a sign of courage in certain cultural or social groups, but this behavior can also mask the severity of the injury to the treating physician.

Depression and anxiety can lower both types of pain thresholds. Anger or worry, however, can temporarily ease or lessen the pain. Feelings of emotional relief can also reduce painful sensations. The context of the pain and the meaning it has for the sufferer also determines how the pain is perceived.

Pain relief

Attempts to relieve pain usually involve both physiological and psychological aspects pain. For example, reducing anxiety may reduce the amount of medication needed to relieve pain. Acute pain is usually the easiest to control; medications and rest are often effective. However, some pain may defy treatment and persist for many years. Such chronic pain can be exacerbated by hopelessness and anxiety.

Opiates are strong painkillers and are used to treat severe pain. Opium, a dried extract obtained from the immature sawdust of the opium poppy (Papaver somniferum), is one of the oldest analgesics. Morphine, a powerful opiate, is an extremely effective pain reliever. These narcotic alkaloids mimic the endorphins produced naturally by the body by binding to their receptors and blocking or reducing the activation of pain neurons. However, the use of opioid painkillers should be monitored not only because they are addictive substances, but also because the patient may become tolerant to them and may require progressively higher doses to achieve the desired level of pain relief. Overdose may cause potentially fatal respiratory depression. Other significant side effects such as nausea and psychological depression when withdrawn, also limit the usefulness of opiates.

Willow bark extracts (genus Salix) contain the active ingredient salicin and have been used since ancient times to relieve pain. Modern non-arcotic anti-inflammatory analgesic salicylates such as aspirin (acetylsalicylic acid) and other anti-inflammatory analgesics such as acetaminophen, nonsteroidal anti-inflammatory drugs (NSAIDs, such as ibuprofen), and cyclooxygenase (COX) inhibitors (such as celecoxib) are less effective than opiates. but are not additive. Aspirin, NSAIDs, and COX inhibitors either nonselectively or selectively block the activity of COX enzymes. COX enzymes are responsible for converting arachidonic acid (a fatty acid) into prostaglandins, which increases sensitivity to pain. Acetaminophen also prevents the formation of prostaglandins, but its activity appears to be limited primarily to the central nervous system and may occur through multiple mechanisms. Drugs known as N-methyl-d-aspartate receptor (NMDAR) antagonists, examples of which include dextromethorphan and ketamine, can be used to treat certain forms of neuropathic pain, such as diabetic neuropathy. The drugs work by blocking NMDARs, whose activation is involved in nociceptive transmission.

Psychotropic medications, including antidepressants and tranquilizers, may be used to treat patients with chronic pain who also suffer from psychological conditions. These medications help reduce anxiety and sometimes change the perception of pain. Pain appears to be relieved by hypnosis, placebos, and psychotherapy. Although the reasons why an individual might report pain relief after taking a placebo or after psychotherapy remains unclear, researchers suspect that the expectation of relief is stimulated by the release of dopamine in an area of the brain known as the ventral striatum. Activity in the abdominal genital organ is associated with increased dopamine activity and is associated with the placebo effect, in which pain relief is reported after placebo treatment.

Specific nerves may be blocked in cases where the pain is limited to an area that has few sensory nerves. Phenol and alcohol are neurolytics that destroy nerves; Lidocaine can be used for temporary pain relief. Surgical separation of the nerves is rarely performed because it can cause serious side effects such as motor loss or relieved pain.

Some pain may be treated through transcutaneous electrical nerve stimulation (TENS), in which electrodes are placed on the skin over the painful area. Stimulation of additional peripheral nerve endings has an inhibitory effect on nerve fibers, causing pain. Acupuncture, compresses and heat treatments can work by the same mechanism.

Chronic pain, defined broadly as pain that persists for at least six months, represents the biggest challenge in pain management. Unable to experience chronic discomfort can cause psychological complications such as hypochondria, depression, sleep disturbances, loss of appetite and feelings of helplessness. Many patient clinics offer a multidisciplinary approach to chronic pain management. Patients with chronic pain may require unique pain management strategies. For example, some patients may benefit from surgical implant. Examples of implants include intrathecal delivery medicine, in which a pump implanted under the skin delivers pain medication directly to the spinal cord, and a spinal cord stimulation implant, in which an electrical device placed in the body sends electrical impulses to the spinal cord to inhibit pain signaling. Other treatment strategies for chronic pain include alternative therapies, physical exercise, physical therapy, cognitive behavioral therapy and TENS.