Fluid And Electrolyte Balance Flashcards
Body fluid compartments:
-fluid contained within the cells= intracellular fluid (ICF)
-cells are contained in a watery internal environment = life-sustaining exchanges are made= extracellular fluid (ECF)
-ECF consists of 2 compartments:
> Blood plasma
> Interstitial fluid (IF)
In a healthy young adult; what % of the body mass is water?
60%
Male at 60%
Female at 50%
What factors affect the total body water in an individual?
-age, body mass, gender + relative amount of fat tissue
Which body tissue has the highest content of water skeletal muscle or fat?
Skeletal muscle is 75% water- most hydrated (fat is 20% water- least hydrated)
Electrolytes and nonelectrolytes- osmotic power:
*water is the universal solvent
What are solutes broadly classed into?
-electrolytes; dissociate in solution into ions, charged- hence conduct electricity
-nonelectrolytes; covalent bonds, no dissociation in solution, no charge
-osmotic power will depend on NUMBER of osmotic particles when a molecule dissolves
*water moves according to osmotic gradients so electrolytes have greatest ability to cause fluid shifts
Electrolytes concentrations (mEq/L)
-electrolyte concentrations= milliequivalent per litre (mEq/l) —> charge
-number of electrical charges per litre of solution
Electrolytes composition of: blood plasma, interstitial fluid + intracellular fluid;
-composition of the extracellular fluids is similar except for protein
-NaK ATPase pump= membrane transporter which maintains the distribution of cations between the ICF and ECF
Primary active transport:
Fluid movement between compartments:
-plasma circulates through the body + links the external environment e.g. lungs, kidney + GIT + the internal compartments
-changes that occur in plasma composition + volume= quickly compensated for by adjustments in IF and ICF
-ICF volume= determined by ECF solute concentration
Water balance; main sources of water intake+ output:
-when input + output are balanced= body is adequately hydrated
-tonicity is maintained within narrow limits of 280-300mosm/kg H20
^values can be affected by:
>drinking 6 cans of beer, 3L of fluids, alcohol inhibits ADH
>and fast in which only water is ingested
Water balance + anti diuretic hormone (ADH)
Water input:
Dehydration:
-osmoreceptors in hypothalamus —> stimulate ADH release from post pituitary gland—> ^ water reabsorption at the kidney —> decreases urine output
Movement of water:
How does antidiuretic hormone (ADH) work?
-ADH causes the principal cells in the collecting duct to insert aquaporins in the apical membrane= increased water reabsorption
-high conc of solutes in the medullary interstitium = osmotic pressure necessary to re absorb water
Water balance + anti diuretic hormone (ADH):
Water output:
Hypo -> low —— hyponatremia ——NATRIUM—> sodium
Osmoreceptors in the hypothalamus —> inhibit ADH release from post pituitary gland —> decreases water reabsorption at the kidney —> increases urine output
What is the role of Na+ in fluid + electrolyte balance?
-sodium salts are the most abundant solutes in the ECF which are responsible for:
>most of ECF/osmotic pressure
>control both volume + distribution of water
>blood pressure
-Na+ transport by the renal tubule cells is linked to K+, Cl-, HCO-3 + H+ concentrations in the ECF
-aldosterone= promotes Na+ reabsorption + water conversion unless other mechanisms favour water loss
