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Cramp
A cramp is a sudden, and involuntary muscle contraction or over-shortening; while generally temporary and non-damaging, they can cause mild-to-excruciating pain, and a paralysis-like immobility of the affected muscle(s). Onset is usually sudden, and it resolves on its own over a period of several seconds, minutes, or hours. Cramps may occur in a skeletal muscle or smooth muscle. Skeletal muscle cramps may be caused by any combination of muscle fatigue, a lack of electrolytes (e.g., low sodium, low potassium, or low magnesium). Cramps of smooth muscle may be due to menstruation or gastroenteritis. ==Differential diagnosis== Causes of cramping include〔(Muscle Cramps Symptoms, Causes, Treatment – Do all muscle cramps fit into the above categories on MedicineNet ). Medicinenet.com. Retrieved on 2011-02-13.〕 hyperflexion, hypoxia, exposure to large changes in temperature, dehydration, or low blood salt. Muscle cramps may also be a symptom or complication of pregnancy, kidney disease, thyroid disease, hypokalemia, hypomagnesemia or hypocalcaemia (as conditions), restless-leg syndrome, varicose veins,〔Bergin J. The Vein Book, Hardcover text, Editor Bergin J , 2007.〕 and multiple sclerosis.〔(Muscle Cramps at WebMD )〕 Electrolyte disturbance may cause cramping and muscle tetany, particularly hypokalemia and hypocalcaemia. This disturbance arises as the body loses large amounts of interstitial fluid through sweat. This interstitial fluid comprises mostly water and salt (sodium chloride). The loss of osmotically active particles outside of muscle cells leads to a disturbance of the osmotic balance and therefore shrinking of muscle cells, as these contain more osmotically active particles. This causes the calcium pump between the muscle sarcoplasm and sarcoplasmic reticulum to short circuit; the calcium ions remain bound to the troponin, continuing muscle contraction. As early as 1965, researchers observed that leg cramps and restless-leg syndrome result from excess insulin, sometimes called hyperinsulinemia. Hypoglycemia and reactive hypoglycemia are associated with excess insulin (or insufficient glucagon), and avoidance of low blood glucose concentration may help to avoid cramps.
抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Cramp」の詳細全文を読む
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