"M.E. is characterized primarily by damage to the central nervous system (the brain) which results in dysfunctions and damage to many of the body’s vital systems and a loss of normal internal homeostasis. Therefore, although Myalgic Encephalomyelitis is primarily neurological, symptoms may be manifested by: cognitive, cardiac, cardiovascular, immunological, endocrinological, respiratory, hormonal, gastrointestinal and musculo-skeletal dysfunctions and damage. More than 64 distinct symptoms have been authentically documented in M.E. Symptoms are also caused by a loss of normal internal homeostasis; the body becomes unable to make all the appropriate physiological adjustments that allow it to maintain homeostatic equilibrium in response to the changes to the internal and external environment that are part of everyday life. The body/brain no longer responds appropriately to homeostatic pressures, including (to varying extents): physical activity, cognitive exertion, sensory input, orthostatic stress, emotional stress and infectious stress.