Pain overview

# Overview
Pain, in the sense of physical pain, is a typical sensory experience that may be described as the unpleasant awareness of a noxious stimulus or bodily harm. Individuals experience pain by various daily hurts and aches, and occasionally through more serious injuries or illnesses. For scientific and clinical purposes, pain is defined by the International Association for the Study of Pain (IASP) as "an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage".
Pain is highly subjective to the individual experiencing it. A definition that is widely used  in nursing was first given as early as 1968 by Margo McCaffery: "'Pain is whatever the experiencing person says it is, existing whenever he says it does".
Pain of any type is the most frequent reason for physician consultation in the United States, prompting half of all Americans to seek medical care annually. It is a major symptom in many medical conditions, significantly interfering with a person's quality of life and general functioning. Diagnosis is based on characterizing pain in various ways, according to duration, intensity, type (dull, burning or stabbing), source, or location in body. Usually pain stops without treatment or responds to simple measures such as resting or taking an analgesic, and it is then called acute pain. But it may also become intractable and develop into a condition called chronic pain, in which pain is no longer considered a symptom but an illness by itself. The study of pain has in recent years attracted many different fields such as pharmacology, neurobiology, nursing sciences, dentistry, physiotherapy, and psychology. Pain medicine is a separate subspecialty figuring under some medical specialties like anesthesiology, physiatry, neurology, psychiatry.
Pain is part of the body's defense system, triggering a reflex reaction to retract from a painful stimulus, and helps adjust behaviour to increase avoidance of that particular harmful situation in the future. Given its significance, physical pain is also linked to various cultural, religious, philosophical, or social issues.

# Historical Perspective
"Pain  (n.) 1297, "punishment," especially for a crime; also (c.1300) "condition one feels when hurt, opposite of pleasure," from O.Fr. peine, from L. poena "punishment, penalty" (in L.L. also "torment, hardship, suffering"), from Gk. poine "punishment," from PIE *kwei- "to pay, atone, compensate" (...)." 

# Pathophysiology
Stimulation of a nociceptor, due to a chemical, thermal, or mechanical event that has the potential to damage body tissue, may cause nociceptivepain.

# Diagnosis

## X Ray
X-rays produce pictures of the body's structures, such as bones and joints

## MRI
Imaging, especially magnetic resonance imaging or MRI, provides physicians with pictures of the body's structures and tissues. MRI uses magnetic fields and radio waves to differentiate between healthy and diseased tissue.

## Other Diagnostic Studies
Electrodiagnostic procedures include electromyography (EMG), nerve conduction studies, and evoked potential (EP) studies. Information from EMG can help physicians tell precisely which muscles or nerves are affected by weakness or pain. Thin needles are inserted in muscles and a physician can see or listen to electrical signals displayed on an EMG machine. With nerve conduction studies the doctor uses two sets of electrodes (similar to those used during an electrocardiogram) that are placed on the skin over the muscles. The first set gives the patient a mild shock that stimulates the nerve that runs to that muscle. The second set of electrodes is used to make a recording of the nerve's electrical signals, and from this information the doctor can determine if there is nerve damage. EP tests also involve two sets of electrodes-one set for stimulating a nerve (these electrodes are attached to a limb) and another set on the scalp for recording the speed of nerve signal transmission to the brain.