Water, Sodium, and Potassium PDF

+ Water,Sodium and Potassium + n Balance – a state of equilibrium – substances are maintained in the right amounts and in the right place in the body + Water Balance n Osmosis is the primary method of water movement into and out of body fluid compartments. n Osmosis is...

+ Water,Sodium and Potassium + n Balance – a state of equilibrium – substances are maintained in the right amounts and in the right place in the body + Water Balance n Osmosis is the primary method of water movement into and out of body fluid compartments. n Osmosis is the net movement of water molecules through a selectively permeable membrane from an area of high water concentration to an area of lower water concentration. + n The concentration of solutes determines the direction of water movement. n Most solutes in the body are electrolytes – inorganic compounds which dissociate into ions in solution. n “Where sodium goes, water follows.” + n About 40 Liters (10.56 gallons) of body water n Babies – 75% water n Men – 63 % n Women – 52% + Fluid compartments n Separated by selectively permeable membranes n Intracellular – 2/3 (63%) of total body water n Extracellular – 1/3 (37%) n Interstitial fluid – 80 % of extracellular water n Blood plasma – 20 % of extracellular water + Composition of compartments n Extracellular fluids: n High in Na+, Cl-, Ca++, HCO3- n Blood plasma has more protein than interstitial fluid and lymph n Intracellular fluids: n High in K+, phosphate, Mg++, and more protein than plasma + Regulation of water intake n Main regulator is thirst. n Dehydration (output>intake) as little as 1% decrease in body water causes: n Decreased production of saliva n Increased blood osmotic pressure – stimulates osmoreceptors in the hypothalamus n Decreased blood volume – renin is produced + Regulation of Water Output n Through regulating urine formation n ADH – production stimulated by ↑ blood tonicity of decrease in volume. nActs on distal convoluted tubules and collecting ducts of kidney – permits reabsorption of water + n Aldosterone – production is stimulated by angiotensin II through renin production n Causes sodium ( and water) to be reabsorbed n ANP – causes sodium (and water) loss when pressure in right atrium is too high + Water imbalances n Dehydration is the imbalance seen most often. n Prolonged diarrhea or vomiting n Excessive sweating