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volume homeostasis

Renal Na excretion. Na is the major extracellular cationIntracellular [Na] is maintained at low levels (10 - 20 mM) by the Na,K-ATPaseThe [Na] in the extracellular fluid is maintained constant (140 mM). Therefore, the amount of Na present in the extracellular space (Na content) is the major determinant of the extracellular fluid volume (ECFV).increased Na content -----> increased ECFVdecreased Na content -----> decreased ECFV.

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volume homeostasis

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    1. Volume Homeostasis Thomas Kleyman, MD

    3. ECFV homeostasis Changes in ECFV are reflected in changes in body weight. To maintain extracellular fluid volume constant, the amount of Na excreted daily by the kidneys must equal the amount of Na ingested daily. Nain = Naout Rates of Na excretion varies with Na intake. There are no normal values for rates of Na excretion. Hormones regulate the extracellular fluid volume by altering renal Na excretion angiotensin II arginine vasopressin aldosterone atrial natriuretic peptide natriuretic factors Ouabain Ouabain analogs

    5. Renal Na Excretion A large amount of Na is filtered on a daily basis

    12. Regulation of Tubular Na+ Transport Hormones regulate the extracellular fluid volume by altering renal Na+ excretion Hormones that enhance tubular Na+ reabsorption angiotensin II arginine vasopressin Aldosterone Hormones that inhibit tubular Na+ reabsorption atrial natriuretic peptide natriuretic factors Ouabain Ouabain analogs

    13. Angiotensin II ? arteriolar vasoconstriction (1) ? glomerular capillary hydrostatic pressure (2) ? glomerular capillary flow rate

    14. Decrease in hydrostatic pressure across the efferent arteriole

    15. Angiotensin II

    17. Volume-mediated Regulation of ADH Secretion

    22. Aldosterone modulates the interaction of Nedd4 with ENaC

    23. Atrial Natriuretic Peptide Increase GFR Increase the amount of Na+ filtered at the glomerulus Inhibit Na+ reabsorption in the inner medullary collecting tubule Inhibits Na,K-ATPase

    24. Ouabain and Related Compounds Synthesized and secreted by hypothalamus and adrenal glands Inhibit Na+ reabsorption Inhibits Na,K-ATPase

    26. Volume Homeostasis Maintain a constant ECF volume Nain = Naout

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