pain mechanism

pain mechanism,

the network that communicates unpleasant sensations and the perceptions of noxious stimuli throughout the body in association with physical disease and trauma involving tissue damage. The gate control theory of pain is an attempt to explain the role of the nervous system in the pain response. It states that pain signals that reach the nervous system excite a group of small neurons that form a "pain pool." When the total activity of these neurons reaches a minimum level, a theoretic gate opens up and allows the pain signals to proceed to higher brain centers. The areas in which the gates operate are considered to be in the spinal cord dorsal horn and the brainstem. The pattern theory holds that the intensity of a stimulus evokes a specific pattern, which is interpreted by the brain as pain. This perception is the result of the intensity and frequency of stimulation of a nonspecific end organ. Some authorities believe that bradykinin and histamine, two chemical substances produced by the body, cause pain. Recently discovered pain killers produced naturally by the body are the enkephalins and the endorphins. Some studies indicate that the enkephalins are 10 times as potent as morphine in reducing pain. It is known that after histamine and some other naturally occurring chemical substances are released in the body, pain sensations travel along fast-conducting and slow-conducting nerve fibers. These pain-transmitting neuropathways communicate the pain sensation to the dorsal root ganglia of the spinal cord and synapse with certain neurons in the posterior horns of the gray matter. The pain sensation is then transmitted to the reticular formation and the thalamus by neurons that form the anterolateral spinothalamic tract. It is then conveyed to various areas of the brain, such as the cortex and the hypothalamus, by synapses at the thalamus. The immediate reaction to pain is transmitted over the reflex arc by sensory fibers in the dorsal horn of the spinal cord and by synapsing motor neurons in the anterior horn. This anatomic pattern of sensory and motor neurons allows the individual to move quickly at the touch of some harmful stimulus, such as extreme heat or cold. Nerve impulses alerting the individual to move away from such stimuli are simultaneously sent along efferent nerve fibers from the brain. Also called gate theory of pain, pain pathway.

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pain,

n an unpleasant sensation created by a noxious stimulus mediated along specific nerve pathways to the central nervous system, where it is interpreted. The sensation of pain is a protective mechanism that warns of danger without giving too much information about the specific nature of the danger. It initiates nociceptive reflexes.

pain and suffering,

n an element in a claim for damages in a liability lawsuit. It requests compensation to an individual for mental and physical pain and discomfort as a result of an injury.

pain, assessment,

n an evaluation of the reported pain and the factors that alleviate or exacerbate a patient's pain; used as an aid in the diagnosis and the treatment of disease and trauma.

pain, chest,

n pain that occurs in the chest region because of disorders of the heart (e.g., angina pectoris, myocardial infarction, or pericarditis), pulmonary artery (pulmonary embolism or hypertension), lungs (pleuritis), esophagus (“heartburn”), abdominal organs (aerophagia, biliary tract disease, splenic infarction, or gaseous distention in the splenic flexure), or the chest wall (neoplasia, costochondral strains, trauma, hyperventilation, or muscular tension).

pain clinic,

n a multidisciplinary association of health care professionals devoted to the diagnosis and treatment of patients with acute and chronic pain.

pain, deep,

n dull, aching, or boring pain originating in muscles, tendons, and joints. It is poorly localized and tends to radiate.

pain dysfunction syndrome,

n in dentistry, a phrase used to describe a condition in patients who appear to have a psychophysiologic basis for stress overload on the temporomandibular joint. The preferred term is
mandibular stress syndrome.

pain, ghost,

n See odontalgia, phantom.

pain mechanism,

n the network that communicates unpleasant sensations and the perceptions of noxious stimuli throughout the body in association with both physical disease and trauma involving tissue damage.

pain, nerve ending,

n a receptor nerve ending that is relatively primitive and ends in an undifferentiated arborization. The nerve ending for the sensation of pain is a protective mechanism that warns of danger without giving too much information about the specific nature of the danger. The danger stimuli give rise to nociceptive reflexes, or defensive, protective, or withdrawal movements. The nociceptive reflexes supersede other, less urgent, reflexes that are thus inhibited.

pain, projected pathologic,

n pain erroneously perceived to arise in a peripheral region because of a stimulus from end-organs supplying the region (e.g., sciatic pain). Actually the stimulus occurred somewhere along the pain pathway from the nerve to the cortex.

pain, reaction,

n the individual's manifestation of the unpleasant sensation.

pain, referred,

n pain caused by an agent in one area but manifested in another (e.g., pain caused by caries in the maxillary third molar may be referred to the mandible, so the source of pain appears to be in the mandible).

pain stimulus,

n an agent that has the potential to induce pain, whether through chemical, mechanical, or thermal means.

pain, tactile stimuli,

n any of a number of physical sources that may aggravate dentin hypersensitivity, such as dental instruments, toothbrush bristles, ill-fitting oral prostheses, and various personal oral habits a patient may have.

pain, thermal stimuli,

n dentin hypersensitivity related to abrupt changes in temperature of teeth as a result of contact with very cold or very hot foods and liquids, rapid intake of air through the oral cavity, and during professional oral hygiene procedures requiring rapid drying of teeth.

pain threshold,

n the point at which a stimulus causes pain. It varies widely among individuals.

pain, tolerance,

n the maximum pain level an individual is able to withstand.