Physiology 261 Chapter 20:Fluid and Electrolyte Balance1.The renal, respiratory and cardiovascular systems control fluid, regulates BP, pH, and electrolyte balance. Behaviors such as drinking also pay an important role.2.Pulmonary and cardiovascular compensations are more rapid than renal compensation.3.ADH stimulates H2O conservation at the kidneys.Urinary: Early Filtrate Processing4.Most water intake comes from food and drink. The largest water loss is 1.5liters/day in urine. Smaller amounts are lost in feces, by evaporation from skin,and in exhaled humidified air.5.Renal water reabsorption conserves water but cannot restore water lost from the body.6.To produce dilute urine, the nephron must reabsorb solute without reabsorbing water. To concentrate urine, the nephron must reabsorb water without reabsorbing solute.7.Filtrate leaving the ascending limb of the loop of Henle is dilute. The final concentration of urine depends on the water permeability of the collecting duct.8.The hypothalamic hormone vasopressin controls collecting duct permeability to water in a graded fashion. When vasopressin absent, water permeability is nearly zero.9.Vasopressin causes distal nephron cells to insert aquaporin water pores in their apical membrane.