HES 250 Lecture Notes - Lecture 9: Evaporation, Nephron, Adrenal Gland
Document Summary
Physiological responses to heat stress integration hypothalamus effectors cutaneous vasodilation sweating. Water loss: rest: 4. 2 ml/h, 5% total, prolonged exercise: 1,200 ml/h, 90. 6% (1. 2 kg per hour lost) Evaporation, not sweat, cools down the body. Factors affecting evaporative heat loss: amount of skin surface exposed to air, convection current around the body (wind, environmental temperature, relative humidity. Sweat loss = body mass before body mass after + fluid consumed. Sweat rate = sweat loss exercise time (min) Dehydration = sweat loss starting weight 100. Can dehydration be avoided by consuming enough water? (no. ) 2. (cid:2873)90 = 0. 278 l/min = 1. 67 l/hr. 2. (cid:2873)7(cid:2872). (cid:2873) 100 = 3: sweat rate: 3. 7 l/hr: gi absorption rate: ~0. 8-1. 2 l/hr. How does dehydration reduce performance: decreased blood volume, decreased venous return, altered electrolyte balance, accelerated glycogen loss. Concerns: decrease in amount of blood supplied to the muscle, decrease in venous return and stroke volume, decrease in blood pressure.
