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62-488: Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage." Pain motivates organisms to withdraw from damaging situations, to protect a damaged body part while it heals, and to avoid similar experiences in

124-486: A decreased appetite and decreased nutritional intake. A change in condition that deviates from baseline, such as moaning with movement or when manipulating a body part, and limited range of motion are also potential pain indicators. In patients who possess language but are incapable of expressing themselves effectively, such as those with dementia, an increase in confusion or display of aggressive behaviors or agitation may signal that discomfort exists, and further assessment

186-417: A cell membrane are isotonic if the concentration of solutes outside the cell is equal to the concentration of solutes inside the cell. In this case the cell neither swells nor shrinks because there is no concentration gradient to induce the diffusion of large amounts of water across the cell membrane. Water molecules freely diffuse through the plasma membrane in both directions, and as the rate of water diffusion

248-486: A credible and convincing signal of the need for relief, help, and care. Idiopathic pain (pain that persists after the trauma or pathology has healed, or that arises without any apparent cause) may be an exception to the idea that pain is helpful to survival, although some psychodynamic psychologists argue that such pain is psychogenic, enlisted as a protective distraction to keep dangerous emotions unconscious. In pain science, thresholds are measured by gradually increasing

310-454: A non-communicative person, observation becomes critical, and specific behaviors can be monitored as pain indicators. Behaviors such as facial grimacing and guarding (trying to protect part of the body from being bumped or touched) indicate pain, as well as an increase or decrease in vocalizations, changes in routine behavior patterns and mental status changes. Patients experiencing pain may exhibit withdrawn social behavior and possibly experience

372-573: A person's quality of life and general functioning. People in pain experience impaired concentration, working memory , mental flexibility , problem solving and information processing speed, and are more likely to experience irritability, depression, and anxiety. Simple pain medications are useful in 20% to 70% of cases. Psychological factors such as social support , cognitive behavioral therapy , excitement, or distraction can affect pain's intensity or unpleasantness. First attested in English in 1297,

434-555: A reduction in negative affect . Across studies, participants that were subjected to acute physical pain in the laboratory subsequently reported feeling better than those in non-painful control conditions, a finding which was also reflected in physiological parameters. A potential mechanism to explain this effect is provided by the opponent-process theory . Before the relatively recent discovery of neurons and their role in pain, various body functions were proposed to account for pain. There were several competing early theories of pain among

496-703: A result of decreased sensation. A much smaller number of people are insensitive to pain due to an inborn abnormality of the nervous system, known as " congenital insensitivity to pain ". Children with this condition incur carelessly-repeated damage to their tongues, eyes, joints, skin, and muscles. Some die before adulthood, and others have a reduced life expectancy. Most people with congenital insensitivity to pain have one of five hereditary sensory and autonomic neuropathies (which includes familial dysautonomia and congenital insensitivity to pain with anhidrosis ). These conditions feature decreased sensitivity to pain together with other neurological abnormalities, particularly of

558-407: A solution outside of a cell is called hypotonic if it has a lower concentration of solutes relative to the cytosol . Due to osmotic pressure , water diffuses into the cell, and the cell often appears turgid , or bloated. For cells without a cell wall such as animal cells, if the gradient is large enough, the uptake of excess water can produce enough pressure to induce cytolysis , or rupturing of

620-446: A state known as pain asymbolia, described as intense pain devoid of unpleasantness, with morphine injection or psychosurgery . Such patients report that they have pain but are not bothered by it; they recognize the sensation of pain but suffer little, or not at all. Indifference to pain can also rarely be present from birth; these people have normal nerves on medical investigations, and find pain unpleasant, but do not avoid repetition of

682-427: Is "pain that extends beyond the expected period of healing". Chronic pain may be classified as " cancer-related " or "benign." Allodynia is pain experienced in response to a normally painless stimulus. It has no biological function and is classified by characteristics of the stimuli as cold, heat, touch, pressure or a pinprick. Phantom pain is pain felt in a part of the body that has been amputated , or from which

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744-698: Is a common, reproducible tool in the assessment of pain and pain relief. The scale is a continuous line anchored by verbal descriptors, one for each extreme of pain where a higher score indicates greater pain intensity. It is usually 10 cm in length with no intermediate descriptors as to avoid marking of scores around a preferred numeric value. When applied as a pain descriptor, these anchors are often 'no pain' and 'worst imaginable pain". Cut-offs for pain classification have been recommended as no pain (0–4mm), mild pain (5–44mm), moderate pain (45–74mm) and severe pain (75–100mm). The Multidimensional Pain Inventory (MPI)

806-494: Is a questionnaire designed to assess the psychosocial state of a person with chronic pain. Combining the MPI characterization of the person with their IASP five-category pain profile is recommended for deriving the most useful case description. Non-verbal people cannot use words to tell others that they are experiencing pain. However, they may be able to communicate through other means, such as blinking, pointing, or nodding. With

868-614: Is a symptom of many medical conditions. Knowing the time of onset, location, intensity, pattern of occurrence (continuous, intermittent, etc.), exacerbating and relieving factors, and quality (burning, sharp, etc.) of the pain will help the examining physician to accurately diagnose the problem. For example, chest pain described as extreme heaviness may indicate myocardial infarction , while chest pain described as tearing may indicate aortic dissection . Functional magnetic resonance imaging brain scanning has been used to measure pain, and correlates well with self-reported pain. Nociceptive pain

930-474: Is also associated with increased depression, anxiety, fear, and anger. If I have matters right, the consequences of pain will include direct physical distress, unemployment, financial difficulties, marital disharmony, and difficulties in concentration and attention… Although pain is considered to be aversive and unpleasant and is therefore usually avoided, a meta-analysis which summarized and evaluated numerous studies from various psychological disciplines, found

992-548: Is caused by stimulation of sensory nerve fibers that respond to stimuli approaching or exceeding harmful intensity ( nociceptors ), and may be classified according to the mode of noxious stimulation. The most common categories are "thermal" (e.g. heat or cold), "mechanical" (e.g. crushing, tearing, shearing, etc.) and "chemical" (e.g. iodine in a cut or chemicals released during inflammation ). Some nociceptors respond to more than one of these modalities and are consequently designated polymodal. International Association for

1054-406: Is distilled water. A hypertonic solution has a greater concentration of non-permeating solutes than another solution. In biology, the tonicity of a solution usually refers to its solute concentration relative to that of another solution on the opposite side of a cell membrane ; a solution outside of a cell is called hypertonic if it has a greater concentration of solutes than the cytosol inside

1116-472: Is essential for protection from injury, and recognition of the presence of injury. Episodic analgesia may occur under special circumstances, such as in the excitement of sport or war: a soldier on the battlefield may feel no pain for many hours from a traumatic amputation or other severe injury. Although unpleasantness is an essential part of the IASP definition of pain, it is possible in some patients to induce

1178-450: Is hypertonic to the fish that live in it. Because the fish need a large surface area in their gills in contact with seawater for gas exchange , they lose water osmotically to the sea from gill cells. They respond to the loss by drinking large amounts of saltwater, and actively excreting the excess salt. This process is called osmoregulation . A hypotonic solution has a lower concentration of solutes than another solution. In biology,

1240-511: Is influenced only by solutes that cannot cross the membrane, as only these exert an effective osmotic pressure. Solutes able to freely cross the membrane do not affect tonicity because they will always equilibrate with equal concentrations on both sides of the membrane without net solvent movement. It is also a factor affecting imbibition . There are three classifications of tonicity that one solution can have relative to another: hypertonic , hypotonic , and isotonic . A hypotonic solution example

1302-401: Is initially described as burning or tingling but may evolve into severe crushing or pinching pain, or the sensation of fire running down the legs or of a knife twisting in the flesh. Onset may be immediate or may not occur until years after the disabling injury. Surgical treatment rarely provides lasting relief. Breakthrough pain is transitory pain that comes on suddenly and is not alleviated by

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1364-505: Is necessary. Changes in behavior may be noticed by caregivers who are familiar with the person's normal behavior. Infants do feel pain , but lack the language needed to report it, and so communicate distress by crying. A non-verbal pain assessment should be conducted involving the parents, who will notice changes in the infant which may not be obvious to the health care provider. Pre-term babies are more sensitive to painful stimuli than those carried to full term. Another approach, when pain

1426-419: Is often described as shooting, crushing, burning or cramping. If the pain is continuous for a long period, parts of the intact body may become sensitized, so that touching them evokes pain in the phantom limb. Phantom limb pain may accompany urination or defecation . Local anesthetic injections into the nerves or sensitive areas of the stump may relieve pain for days, weeks, or sometimes permanently, despite

1488-409: Is suspected, is to give the person treatment for pain, and then watch to see whether the suspected indicators of pain subside. The way in which one experiences and responds to pain is related to sociocultural characteristics, such as gender, ethnicity, and age. An aging adult may not respond to pain in the same way that a younger person might. Their ability to recognize pain may be blunted by illness or

1550-432: Is the same in each direction, the cell will neither gain nor lose water. An iso-osmolar solution can be hypotonic if the solute is able to penetrate the cell membrane. For example, an iso-osmolar urea solution is hypotonic to red blood cells, causing their lysis . This is due to urea entering the cell down its concentration gradient, followed by water. The osmolarity of normal saline , 9 grams NaCl dissolved in water to

1612-523: The autonomic nervous system . A very rare syndrome with isolated congenital insensitivity to pain has been linked with mutations in the SCN9A gene, which codes for a sodium channel ( Na v 1.7 ) necessary in conducting pain nerve stimuli. Experimental subjects challenged by acute pain and patients in chronic pain experience impairments in attention control, working memory capacity , mental flexibility , problem solving, and information processing speed. Pain

1674-405: The medial , paleospinothalamic tract . The neospinothalamic tract carries the fast, sharp A-delta signal to the ventral posterolateral nucleus of the thalamus . The paleospinothalamic tract carries the slow, dull C fiber pain signal. Some of the paleospinothalamic fibers peel off in the brain stem—connecting with the reticular formation or midbrain periaqueductal gray—and the remainder terminate in

1736-508: The primary and secondary somatosensory cortex . Spinal cord fibers dedicated to carrying A-delta fiber pain signals and others that carry both A-delta and C fiber pain signals to the thalamus have been identified. Other spinal cord fibers, known as wide dynamic range neurons , respond to A-delta and C fibers and the much larger, more heavily myelinated A-beta fibers that carry touch, pressure, and vibration signals. Ronald Melzack and Patrick Wall introduced their gate control theory in

1798-472: The 1965 Science article "Pain Mechanisms: A New Theory". The authors proposed that the thin C and A-delta (pain) and large diameter A-beta (touch, pressure, vibration) nerve fibers carry information from the site of injury to two destinations in the dorsal horn of the spinal cord, and that A-beta fiber signals acting on inhibitory cells in the dorsal horn can reduce the intensity of pain signals sent to

1860-445: The 19th-century development of specificity theory . Specificity theory saw pain as "a specific sensation, with its own sensory apparatus independent of touch and other senses". Another theory that came to prominence in the 18th and 19th centuries was intensive theory , which conceived of pain not as a unique sensory modality, but an emotional state produced by stronger than normal stimuli such as intense light, pressure or temperature. By

1922-414: The C fibers. These A-delta and C fibers enter the spinal cord via Lissauer's tract and connect with spinal cord nerve fibers in the central gelatinous substance of the spinal cord . These spinal cord fibers then cross the cord via the anterior white commissure and ascend in the spinothalamic tract . Before reaching the brain, the spinothalamic tract splits into the lateral , neospinothalamic tract and

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1984-596: The Study of Pain The International Association for the Study of Pain ( IASP ) is an international learned society promoting research, education, and policies for the understanding, prevention, and treatment of pain . IASP was founded in 1973 under the leadership of John J. Bonica . Its secretariat, formerly based in Seattle, Washington , is now located in Washington, D.C. It publishes

2046-428: The affective-motivational dimension. Thus, excitement in games or war appears to block both the sensory-discriminative and affective-motivational dimensions of pain, while suggestion and placebos may modulate only the affective-motivational dimension and leave the sensory-discriminative dimension relatively undisturbed. (p. 432) The paper ends with a call to action: "Pain can be treated not only by trying to cut down

2108-403: The ancient Greeks: Hippocrates believed that it was due to an imbalance in vital fluids . In the 11th century, Avicenna theorized that there were a number of feeling senses, including touch, pain, and titillation. In 1644, René Descartes theorized that pain was a disturbance that passed along nerve fibers until the disturbance reached the brain. The work of Descartes and Avicenna prefigured

2170-467: The brain no longer receives signals. It is a type of neuropathic pain. The prevalence of phantom pain in upper limb amputees is nearly 82%, and in lower limb amputees is 54%. One study found that eight days after amputation, 72% of patients had phantom limb pain, and six months later, 67% reported it. Some amputees experience continuous pain that varies in intensity or quality; others experience several bouts of pain per day, or it may reoccur less often. It

2232-505: The brain. In 1968, Ronald Melzack and Kenneth Casey described chronic pain in terms of its three dimensions: They theorized that pain intensity (the sensory discriminative dimension) and unpleasantness (the affective-motivational dimension) are not simply determined by the magnitude of the painful stimulus, but "higher" cognitive activities can influence perceived intensity and unpleasantness. Cognitive activities may affect both sensory and affective experience, or they may modify primarily

2294-520: The cell wall at points called plasmodesmata . The cells often take on the appearance of a pincushion , and the plasmodesmata almost cease to function because they become constricted, a condition known as plasmolysis . In plant cells the terms isotonic, hypotonic and hypertonic cannot strictly be used accurately because the pressure exerted by the cell wall significantly affects the osmotic equilibrium point. Some organisms have evolved intricate methods of circumventing hypertonicity. For example, saltwater

2356-435: The cell. When a cell is immersed in a hypertonic solution, osmotic pressure tends to force water to flow out of the cell in order to balance the concentrations of the solutes on either side of the cell membrane. The cytosol is conversely categorized as hypotonic, opposite of the outer solution. When plant cells are in a hypertonic solution, the flexible cell membrane pulls away from the rigid cell wall , but remains joined to

2418-426: The cell. When plant cells are in a hypotonic solution, the central vacuole takes on extra water and pushes the cell membrane against the cell wall. Due to the rigidity of the cell wall, it pushes back, preventing the cell from bursting. This is called turgor pressure . A solution is isotonic when its effective osmole concentration is the same as that of another solution. In biology, the solutions on either side of

2480-413: The drug wearing off in a matter of hours; and small injections of hypertonic saline into the soft tissue between vertebrae produces local pain that radiates into the phantom limb for ten minutes or so and may be followed by hours, weeks, or even longer of partial or total relief from phantom pain. Vigorous vibration or electrical stimulation of the stump, or current from electrodes surgically implanted onto

2542-425: The future. Most pain resolves once the noxious stimulus is removed and the body has healed, but it may persist despite removal of the stimulus and apparent healing of the body. Sometimes pain arises in the absence of any detectable stimulus, damage or disease. Pain is the most common reason for physician consultation in most developed countries. It is a major symptom in many medical conditions, and can interfere with

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2604-399: The intensity of a stimulus in a procedure called quantitative sensory testing which involves such stimuli as electric current , thermal (heat or cold), mechanical (pressure, touch, vibration), ischemic , or chemical stimuli applied to the subject to evoke a response. The " pain perception threshold " is the point at which the subject begins to feel pain, and the "pain threshold intensity" is

2666-435: The intralaminar nuclei of the thalamus. Pain-related activity in the thalamus spreads to the insular cortex (thought to embody, among other things, the feeling that distinguishes pain from other homeostatic emotions such as itch and nausea) and anterior cingulate cortex (thought to embody, among other things, the affective/motivational element, the unpleasantness of pain), and pain that is distinctly located also activates

2728-416: The likelihood of reporting pain. Patients may feel that certain treatments go against their religious beliefs. They may not report pain because they feel it is a sign that death is near. Many people fear the stigma of addiction, and avoid pain treatment so as not to be prescribed potentially addicting drugs. Many Asians do not want to lose respect in society by admitting they are in pain and need help, believing

2790-573: The mid-1890s, specificity was backed primarily by physiologists and physicians, and psychologists mostly backed the intensive theory . However, after a series of clinical observations by Henry Head and experiments by Max von Frey , the psychologists migrated to specificity almost en masse. By the century's end, most physiology and psychology textbooks presented pain specificity as fact. Some sensory fibers do not differentiate between noxious and non-noxious stimuli, while others (i.e., nociceptors ) respond only to noxious, high-intensity stimuli. At

2852-604: The motto "The Relief of Pain Should be a Human Right". Every year, the focus is on another aspect of pain. The World Congress on Pain is the largest global gathering of pain professionals. This event brings together more than 7,000 scientists, clinicians, and healthcare providers from around the world and across pain disciplines.. The program comprises plenary sessions, workshops, poster sessions, and refresher courses, and attendees may receive continuing medical education credits. hypertonic Unlike osmotic pressure, tonicity

2914-480: The noxious stimulus is removed or the underlying damage or pathology has healed. But some painful conditions, such as rheumatoid arthritis , peripheral neuropathy , cancer , and idiopathic pain, may persist for years. Pain that lasts a long time is called " chronic " or "persistent", and pain that resolves quickly is called " acute ". Traditionally, the distinction between acute and chronic pain has relied upon an arbitrary interval of time between onset and resolution;

2976-702: The pain should be borne in silence, while other cultures feel they should report pain immediately to receive immediate relief. Gender can also be a perceived factor in reporting pain. Gender differences can be the result of social and cultural expectations, with, in some cultures, women expected to be more emotional and show pain, and men to be more stoic. As a result, female pain may be at a higher risk of being stigmatized, leading to less urgent treatment of women based on social expectations of their ability to accurately report it. This has been postulated to lead to extended emergency room wait times for women and frequent dismissal of their ability to accurately report pain. Pain

3038-485: The pain stimulus. Insensitivity to pain may also result from abnormalities in the nervous system . This is usually the result of acquired damage to the nerves, such as spinal cord injury , diabetes mellitus ( diabetic neuropathy ), or leprosy in countries where that disease is prevalent. These individuals are at risk of tissue damage and infection due to undiscovered injuries. People with diabetes-related nerve damage, for instance, sustain poorly-healing foot ulcers as

3100-495: The patient's regular pain management . It is common in cancer patients who often have background pain that is generally well-controlled by medications, but who also sometimes experience bouts of severe pain that from time to time "breaks through" the medication. The characteristics of breakthrough cancer pain vary from person to person and according to the cause. Management of breakthrough pain can entail intensive use of opioids , including fentanyl . The ability to experience pain

3162-511: The peripheral end of the nociceptor, noxious stimuli generate currents that, above a given threshold, send signals along the nerve fiber to the spinal cord. The "specificity" (whether it responds to thermal, chemical, or mechanical features of its environment) of a nociceptor is determined by which ion channels it expresses at its peripheral end. So far, dozens of types of nociceptor ion channels have been identified, and their exact functions are still being determined. The pain signal travels from

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3224-490: The periphery to the spinal cord along A-delta and C fibers. Because the A-delta fiber is thicker than the C fiber, and is thinly sheathed in an electrically insulating material ( myelin ), it carries its signal faster (5–30  m/s ) than the unmyelinated C fiber (0.5–2 m/s). Pain evoked by the A-delta fibers is described as sharp and is felt first. This is followed by a duller pain—often described as burning—carried by

3286-474: The question of why pain should have the quality of being painful. He describes the alternative as a mental raising of a "red flag". To argue why that red flag might be insufficient, Dawkins argues that drives must compete with one another within living beings. The most "fit" creature would be the one whose pains are well balanced. Those pains which mean certain death when ignored will become the most powerfully felt. The relative intensities of pain, then, may resemble

3348-535: The relative importance of that risk to our ancestors. This resemblance will not be perfect, however, because natural selection can be a poor designer . This may have maladaptive results such as supernormal stimuli . Pain, however, does not only wave a "red flag" within living beings but may also act as a warning sign and a call for help to other living beings. Especially in humans who readily helped each other in case of sickness or injury throughout their evolutionary history, pain might be shaped by natural selection to be

3410-505: The scientific journal PAIN, PAIN Reports and PAIN: Clinical Updates. IASP currently has more than 7,200 members from 133 countries and in 94 chapters worldwide. IASP supports 20 Special Interest Groups (SIGs) which members may join to network and collaborate with others in their specific field of research or practice. In 2004, supported by various IASP chapters and federations holding their own local events and activities worldwide, IASP initiated its first "Global Year Against Pain" with

3472-650: The sensory input by anesthetic block, surgical intervention and the like, but also by influencing the motivational-affective and cognitive factors as well." (p. 435) Pain is part of the body's defense system, producing a reflexive retraction from the painful stimulus, and tendencies to protect the affected body part while it heals, and avoid that harmful situation in the future. It is an important part of animal life, vital to healthy survival. People with congenital insensitivity to pain have reduced life expectancy . In The Greatest Show on Earth: The Evidence for Evolution , biologist Richard Dawkins addresses

3534-532: The spinal cord, all produce relief in some patients. Mirror box therapy produces the illusion of movement and touch in a phantom limb which in turn may cause a reduction in pain. Paraplegia , the loss of sensation and voluntary motor control after serious spinal cord damage, may be accompanied by girdle pain at the level of the spinal cord damage, visceral pain evoked by a filling bladder or bowel, or, in five to ten percent of paraplegics, phantom body pain in areas of complete sensory loss. This phantom body pain

3596-403: The stimulus intensity at which the stimulus begins to hurt. The " pain tolerance threshold" is reached when the subject acts to stop the pain. A person's self-report is the most reliable measure of pain. Some health care professionals may underestimate pain severity. A definition of pain widely employed in nursing, emphasizing its subjective nature and the importance of believing patient reports,

3658-456: The two most commonly used markers being 3 months and 6 months since the onset of pain, though some theorists and researchers have placed the transition from acute to chronic pain at 12 months. Others apply "acute" to pain that lasts less than 30 days, "chronic" to pain of more than six months' duration, and "subacute" to pain that lasts from one to six months. A popular alternative definition of "chronic pain", involving no arbitrarily fixed duration,

3720-408: The use of medication . Depression may also keep older adult from reporting they are in pain. Decline in self-care may also indicate the older adult is experiencing pain. They may be reluctant to report pain because they do not want to be perceived as weak, or may feel it is impolite or shameful to complain, or they may feel the pain is a form of deserved punishment. Cultural barriers may also affect

3782-550: The word peyn comes from the Old French peine , in turn from Latin poena meaning "punishment, penalty" (also meaning "torment, hardship, suffering" in Late Latin) and that from Greek ποινή ( poine ), generally meaning "price paid, penalty, punishment". The International Association for the Study of Pain recommends using specific features to describe a patient's pain: Pain is usually transitory, lasting only until

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3844-551: Was introduced by Margo McCaffery in 1968: "Pain is whatever the experiencing person says it is, existing whenever he says it does". To assess intensity, the patient may be asked to locate their pain on a scale of 0 to 10, with 0 being no pain at all, and 10 the worst pain they have ever felt. Quality can be established by having the patient complete the McGill Pain Questionnaire indicating which words best describe their pain. The visual analogue scale

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