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Chapter 20, part B

Chapter 20, part B. Integrative Physiology II: Fluid and Electrolyte Balance. Sodium Recycling: Recycling and Excretion. Ascending loop of Henle H 2 O impermeable Na + Active Transport To ECF Gradient Diffuses to blood Collecting Duct: Aldosterone regulates

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Chapter 20, part B

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  1. Chapter 20, part B Integrative Physiology II: Fluid and Electrolyte Balance

  2. Sodium Recycling: Recycling and Excretion • Ascending loop of Henle • H2O impermeable • Na+ Active Transport • To ECF • Gradient • Diffuses to blood • Collecting Duct: • Aldosterone regulates • Na+ recycled or excreted

  3. Mechanism of Na+ Selective Reabsorption in Collecting Duct • Aldosterone: steroid H from adrenal cortex • Stimulates Na+ uptake (& K+ secretion) •  channel synthesis

  4. Mechanism of Na+ Selective Reabsorption in Collecting Duct Figure 20-12: Aldosterone action in principal cells

  5. Angiotensin Pathway: Maintains BP , Volume & Osmolarity Angiotensinogen, ANGI, ANG II, rennin, & ACE Figure 20-13: The renin-angiotensin-aldosterone pathway

  6. Artial Natruretic Peptide: Regulates Na+ & H2O Excretion • Hormone from myocardial cells • Stimulates: hypothalamus, kidney, adrenal, & medulla

  7. Artial Natruretic Peptide: Regulates Na+ & H2O Excretion Figure 20-15: Atrial natriuretic peptide

  8. Potassium Balance: Critical for Excitable Heart & Nervous Tissues • Hypokalemia – low [K+] in ECF, Hyperkalemia - high [K+] • Reabsorbed in Ascending Loop, secreted in Collecting duct

  9. Potassium Balance: Critical for Excitable Heart & Nervous Tissues Figure 20-4: Osmolarity changes as fluid flows through the nephron

  10. Potassium Balance: Critical for Excitable Heart & Nervous Tissues Figure 20-12: Aldosterone action in principal cells

  11. Response to Dehydration & Osmolarity Imbalance • Thirst & "salt craving", or avoidance behavior • Integrated circulatory & excretory reflexes PLAY Animation: Fluids & Electrolytes: Water Homeostasis

  12. Response to Dehydration & Osmolarity Imbalance Figure 20-17 : Homeostatic compensation for severe dehydration

  13. Acid/Base Homeostasis: Overview • Acidosis:  plasma pH • Protein damage • CNS depression • Alkalosis:  plasma pH • Hyperexcitability • CNS & heart • Buffers: HCO3- & proteins • H+ input: diet & metabolic • H+ output: lungs & kidney

  14. Acid/Base Homeostasis: Overview PLAY Animation: Fluids & Electrolytes: Acid/Base Homeostasis Figure 20-18: Hydrogen balance in the body

  15. Kidney Hydrogen Ion Balancing: Proximal Tubule • H+ & NH4+ secreted into lumen and excreted • HCO3- is reabsorbed

  16. Kidney Hydrogen Ion Balancing: Proximal Tubule Figure 20-21: Proximal tubule secretion and reabsorption of filtered HCO3-

  17. Kidney Hydrogen Ion Balancing: Collecting Duct • Type A Intercalated cells excrete H+ absorb HCO3- • Type B intercalated cells absorb H+ secrete HCO3-

  18. Kidney Hydrogen Ion Balancing: Collecting Duct Figure 20-22: Role of the intercalated cell in acidosis and alkalosis

  19. Summary • Electrolyte balance depends on integration of circulatory, excretory and behavioral physiology • Water recycling and ECF/plasma balance depends on descending loop of Henle and vasopressin regulated collecting duct for conservation • Osmolarity depends on aldosterone and angiotensin pathway to regulate CNS & endocrine responses • Along with respiration, proximal tubule and collecting duct cells reabsorb or excrete H+ & HCO3- to balance pH

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