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Fluid and electrolyte balance

Fluid and electrolyte balance. Chapter 27. Fluid compartments & balance. Barriers. Separation of intracellular fluid, interstitial fluid & blood plasma by: Plasma membrane Selectively permeable Active transport pumps Blood vessel walls Only capillaries are leaky enough

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Fluid and electrolyte balance

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  1. Fluid and electrolyte balance Chapter 27

  2. Fluid compartments & balance

  3. Barriers • Separation of intracellular fluid, interstitial fluid & blood plasma by: • Plasma membrane • Selectively permeable • Active transport pumps • Blood vessel walls • Only capillaries are leaky enough • Water & solutes: plasma  interstitial fluid

  4. Fluid balance • Water- largest component of body • 45-75% total body mass • Compartmental exchange allowed by • Filtration • Reabsorption • Diffusion • Osmosis* primary means of movement between ICF & Interstitial fluid AND [solute] dictates direction of movement • Electrolytes = any cmpd that separates into ions when dissolved in water & conducts electricity • most solutes  fluid balance strongly related to electrolytes

  5. Daily water sources • Metabolic water- mainly produced by aerobic cellular respiration • Water loss>gain = dehydration • Thirst center in hypothalamus

  6. Pathway for dehydration stimulating thirst • Figure 27.3

  7. Hormonal regulation of Na+ & Cl- reabsorption • 3 main hormones: • Angiotensin II • Aldosterone • Both promote urinary absorption of Na and Cl  osmosis • Atrial Natriuretic Peptide (ANP) • Promotes natriuresis:  Na (& Cl) excretion followed by water •  renin  angiotensin

  8. Water loss regulation • ADH (AKA vasopressin) • Released due to  osmolarity of body fluids •  osm also stimulates thirst mechanism • promotes insertion of aquaporin-2 collecting ducts • Secreted large  blood volume • Other conditions cause release: • Hyperventilation, vomiting, diarrhea, fever, heavy sweating, destruction of skin thru burns

  9. Series of events in water intoxication: • Is a state in which excessive body water causes cells to swell • Figure 27.5

  10. 4 general electrolyte functions • Control osmosis between fluid compartments • Help maintain acid-base balance • Carry electrical currents • Serve as cofactors for enzyme activity

  11. [Electrolyte & anion] in ECF & ICF

  12. Acid-base balance • Maintain 7.35-7.45 blood pH • Removal & elimination of H+ by: • 1. Buffer systems • Protein- Hb, amino & carboxyl groups • Carbonic acid- in blood • Phosphate- mainly in cytosol, also ECF, urine • 2. Exhalation of carbon dioxide • 3. Kidney excretion of H+

  13. Negative feedback regulation of blood pH by the respiratory system • Exhalation of carbon dioxide lowers the H+ concentration in blood

  14. Secretion of H+ by intercalated cells in the collecting duct • Urine can be 1000x more acidic than blood due to proton pumps

  15. Imbalances– table 27.4 • Effects of acidosis: • CNS depression thru  synaptic transmission • Severe: pH  7 =disorientationcomatosedeath • Effects of alkalosis: • Overexcitability in CNS & peripheral nerves • Nervousness, spasms, convulsions, death • Compensation • Respiratory- hyper or hypoventilation • Renal-Δ H+ secretion or HCO3- reabsorption

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