Blood will pool in tissues, less blood in vessels Pleural Effusion : liters of fluid accumulate in pleural cavity, caused by some lung infections Remember - the body does not store water
24-15 Electrolyte Balance Physiological functions of electrolyte s 1. Chemically reactive and participate in metabolism 2. Dictate electrical membrane potential of the cell 3. Strongly affect osmolarity of body fluids 4. Affect body’s total H 2 O content and distribution Major cation electrolytes Na + , K + , Ca 2+ , Mg 2+ , and H + hormonal control by ALDO, ANP, ADH, PTH Major anion electrolytes Cl − , HCO 3 − (bicarbonate) , and PO 4 3− (phosphate)
24-16 Intracellular Fluid Blood Plasma ( ≅ ECF) Electrolyte Balance Blood Plasma and ICF have similar osmolarity, 300 mOsm but very different individual electrolyte concentrations Note: ECF electrolyte concentrations slightly differ than those in plasma.
24-17 Sodium Homeostasis Na + principal cation in ECF; Na + (Cl - ) account for 90-95% ECF osmolarity Na + deficiency rare; primary concern is excretion of excess dietary Na + Kidney - primary organ that regulates Na + excretion and Na + balance Na+ is the most significant solute in regulating total body H 2 O and distribution of H 2 O among fluid compartments Regulation of plasma Na+ is integrated with regulation of blood osmolarity, H 2 O balance and blood pressure - 3 primary hormones control this integrative regulation Aldosterone (ALDO ) Antidiuretic Hormone ( ADH ), aka Vasopressin Atrial Natriuretic Peptide ( ANP ) and other NPs FYI: Adults need ~500 mg Na + /day; US adult eats 3000-7000 mg/day
24-18 Sodium Homeostasis: Role of Aldosterone Aldosterone, mineralocorticoid secreted by adrenal cortex Primary role in regulating Na+ excretion (not H 2 O balance) Hyponatremia directly stimulates ALDO secretion Hyperkalemia directly stimulates ALDO secretion Hypotension ALDO secretion by Renin-Angiotensin-ALDO system Where does Aldosterone act? binds to receptors in … Ascending Limb of Nephron Loop, Distal Convoluted Tubule, and Cortical portion of Collecting Duct Mechanism of action - ALDO is a steroid binds nuclear receptors, elicits ... Na + ,K + -ATPase gene transcription new Na + pumps synthesized Na+ pumps inserted in plasma membrane ... Tubular reabsorption of Na +
24-19 Action of Aldosterone “salt-retaining hormone” Net effects: Na + reabsorption; Cl- & H 2 O passively follow Na + but also … secretion of K + and H + thus, urine contains less Na & Cl, but more K+ and H+ (acidic) - *urine could contain no Na+ What about increases in BP? BP inhibits R-A-A system no ALDO DCT/CD do not reabsorb Na + urine HIGH in Na + Aldosterone does not change plasma Na concentration because H 2 O follows
23-20 Hormonal Regulation Salt & H 2 O reabsorption in DCT & PCT ADH alters plasma Na+ concnetration. How? ADH regulates water excretion independently of Na+ excretion - thereby, ADH increases blood Na+ conc.
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- Spring '18
- pH, ICF, Bicarbonate, buffer solution