Sweating is controlled by the autonomic nervous system, which has both sympathetic and parasympathetic divisions. The sympathetic division of the ANS controls involuntary or “autonomic” functions such as digestion, heart rate, breathing rate—both inspiration and expiration—and vasomotor tone (excess sweating). The parasympathetic division regulates all involuntary systems except the cardiovascular system; it modulates these involuntary functions through release of acetylcholine at postganglionic nerve endings. Sweat glands derive their primary secretions from eccrine sweat glands located in hair follicles throughout most skin folds. This type of sweat contains water-soluble electrolytes that are lost when a person sweats—a process referred to as evaporation. Another component of eccrine sweat is urea [N(CH 3 ) 2 NH 2 ], which is metabolically oxidized over time to ammonia [NH 3 ]. Ammonia leads to immediate hypersensitivity reactions when contact occurs with eyes or mucous membranes but does not elicit a reaction in others unless large amounts are present in the body.
To better understand how sweating works under normal conditions, let’s take a look at what happens during ordinary exercise: During prolonged exercise many times there will be several days where you do not perspire much because your body consumes more oxygen than it produces so you begin using up stored reserves before they run out completely. In this case your ability to produce sweat decreases due to reduced blood flow