fluid,electrolyte,pHbalance - Fluids, Electrolytes, pH...

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Fluids, Electrolytes, pH balance Basic Concepts Homeostatic mechanisms regulating fluid volume and composition focus on extracellular fluids (tissue fluid and plasma) No receptors directly monitor fluid or electrolyte composition Cannot tell how many liters of water are in the body Cannot tell how many grams of Na, K, etc. in the body Can detect plasma volume and osmotic concentration (hypothalamus) Water only moves by Osmosis (not actively transported) Therefore, it is inextricably associated with electrolytes Water and electrolyte content/concentration is a balance of gain (dietary) and loss (mostly thru digestive and urinary systems) If gain exceeds loss content/concentration increases If loss exceeds gain content/concentration decreases Water Balance Gain vs. Loss o Metabolic generation of intracellular fluid gain extracellular fluid o Absorption across digestive epithelium gain extracellular fluid o Sensible perspiration loss of extracellular fluid o Defecation loss of extracellular fluid o Respiratory functions and Insensible perspiration loss of extracellular fluid *Gain/Loss both equal ~2.5L/day, which balances the water composition Water Regulation o Regulation of Intake-mostly governed by thirst Need for water sensed by osmoreceptors in hypothalamus These receptors sense solute concentrations of plasma and CSF when solute concentration increases, sign of need more water volume Hypothalamus is also sensitive to Angiotensin II-result of renin release by juxtaglomerular cells when they detect decreasing blood pressure, which would also suggest more water is needed. Sends signal to the cerebrum to generate the sensation of thirst ADH is released more water reabsorbed at the DCT and CD o Regulation of Output-mainly governed by urine volume regulation Water reabsorbed or excreted by the kidney controlled by: Sodium gain/loss
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This note was uploaded on 03/22/2009 for the course BIOL 252 taught by Professor Johnson during the Spring '07 term at UNC.

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fluid,electrolyte,pHbalance - Fluids, Electrolytes, pH...

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