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16 Cards in this Set
- Front
- Back
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Normal plasma osmolality |
287 +/-7 mOsm/kgH2O |
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Response to cell osmotic environment |
Only intestines & brain: Swelling -> extrusion of cellular electrolytes [mostly K+] Shrinkage -> uptake of electrolytes |
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Osmoregulation |
Amount of Na is regulated by the amount of H2O => keeping ICFV constant |
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Hypo-/hypernatremia causes |
Renal: Oligouria -> Hyponatremia (-> swollen cells) Polyuria -> Hypernatremia (-> shrunken cells) Extra-renal: Hyponatremia -> polyuria Hypernatremia -> oligouria (dehydration) |
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Osmoreceptors |
Leaky parts of BBB: subfornical organ organum vasculosum of the lamina terminalis (OVLT) -> ADH, thirst Overhydration: Cold R's in mouth, stretch R's in esophagus & stomach |
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Volumetric control of ADH & thirst |
Usually ICFV > ECFV [importance] hypovolemic/hemorrhagic shock: circulatory collapse > plasma osmolarity -> non-osmotic regulation of ADH & thirst Vol ctrl of ADH & thirst: CV osmoreceptors Plasma ANP (-| ADH), AII (thirst) -> hypothalamus |
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Dilution/concentration of urine |
ADH -> CD H2O permeable, urea gradient Countercurrent exchangers = vasa recta (min Na is carried away) -> hyperosmolality of medulla is preserved Countercurrent multiplication in LH -> axial [salt] gradient caused by "single effect" (Na w/o H2O) |
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Oligouria causes |
Renal failure -> plasma creatinine & BUN both inc. Dehydration -> creatinine constant, BUN inc. |
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ADH actions |
ADH -> CD H2O permeable, urea gradient Efferent arterioles constriction (long-looped nephrons) -> inc. filtration -> NaCl reabsorption reduces BF in vasa recta -> preserves interstitial osmotic gradient stimulates Na reabsorption in AL of long-looped nephrons -> countercurrent multiplication |
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Other water resorption modulators |
ANP - inhibits Na reabsorption in CD, ADH antagonist Prostoglandins x ADH [Ca] x ADH in CD (prevention of kidney stones) |
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(Solute) Free water clearance (C[H2O]) |
C[H2O] the difference in water amount (+/-) between urine & plasma C[H2O] = V[dot] - C[osm] C[osm] = amount of plasma w/o all solutes /time: C[osm] = (U[osm]*V[dot]) / P[osm] Urine osm -> plasma osmolality |
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Electrolyte-free H2O clearance (C[EFH2O]) |
Difference b/w urine flow & the clearance of effective osmoles (~ Na, K, Ca, albumin, etc.) C[EFH2O] = V[dot] - C[eff,osm] Urine composition -> cell volume |
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Diabetes insipidus (DI) |
Lack of ADH action in the kidney Central - inadequate ADH production Nephrogenic - lack of response to ADH |
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Primary polydipsia |
Excessive thirst (psychogenic DI) Threshold: thirst < ADH |
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Syndrome of Inappropriate ADH Secretion (SIADH) |
~ inappropriate antidiuresis
- ectopic production of ADH (tumors) -> low [Na] - inadequate ADH secretion suppression from neurohypophysis - ADH R mutations |
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"Perceived volume depletion" |
When ECFV ↑ but perfusion inadequate -> heart failure => ADH release while ECFV >/= normal |
