Water, Electrolytes & Acid/Base Balance S.G #3

1. Average Water Percentage in Fluid Compartments

  • Intracellular fluid (ICF): ~65%

  • Extracellular fluid (ECF): ~35% (including plasma ~8% and interstitial fluid ~25%)

2. Electrolytes and Water Distribution

  • Electrolytes create osmotic gradients that draw water into specific compartments, balancing total water content and distribution.

3. Water Gains and Losses

  • Gain: Ingestion (liquids, food) and metabolic water

  • Loss: Urine, sweat, breath, feces

4. Metabolic Water

  • Water produced internally as a byproduct of metabolic reactions, such as cellular respiration.

5. Effects of Dehydration

  • Decreases blood volume, increases osmolarity, impairs cellular functions, leads to dry skin, reduced urine output, and, in severe cases, organ failure.

6. Hormones Involved in Thirst

  • ADH (antidiuretic hormone), angiotensin II, aldosterone

7. Short-term vs. Long-term Satiation Mechanisms

  • Short-term: Cooling and moistening of mouth, stomach distension

  • Long-term: Restores blood osmolarity, lasting effect on hydration

8. Kidney Regulation of Urine Volume

  • Adjusting reabsorption of water and electrolytes based on signals from hormones like ADH, aldosterone, and ANP.

9. Aquaporins

  • Water channels in cell membranes that facilitate water transport, especially in kidney tubules.

10. Volume Depletion vs. Dehydration

  • Volume depletion: Loss of water and solutes (e.g., hemorrhage)

  • Dehydration: Loss of water only, leading to hyperosmolarity (e.g., sweating)

11. Infant Vulnerability to Dehydration

  • Higher metabolic rate, greater body surface-to-volume ratio, immature kidneys.

12. Effects of Fluid Deficiency

  • Decreased blood volume, impaired cellular function, risk of shock, and organ damage.

13. Volume Excess vs. Hypotonic Hydration

  • Volume excess: Excess fluid with normal osmolarity (e.g., kidney failure)

  • Hypotonic hydration: Excess water dilutes electrolytes, can cause cellular swelling (e.g., overhydration)

14. Fluid Sequestration

  • Abnormal fluid accumulation in compartments (e.g., edema, ascites).

15. Major Cations and Anions

  • Cations: Sodium (Na⁺), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺)

  • Anions: Chloride (Cl⁻), bicarbonate (HCO₃⁻), phosphate (PO₄³⁻)

16. Sodium Functions

  • Main ECF cation, maintains osmolarity, nerve impulses, muscle contraction.

17. Sodium Homeostasis Mechanisms

  • Regulated by aldosterone, ADH, ANP to adjust reabsorption or excretion.

18. Hypernatremia and Hyponatremia

  • Hypernatremia: Excess sodium, causes dehydration symptoms

  • Hyponatremia: Low sodium, causes neurological issues (e.g., confusion)

19. Potassium Functions

  • Intracellular cation, nerve function, muscle contraction, protein synthesis.

20. Potassium Homeostasis Mechanisms

  • Aldosterone promotes potassium excretion; kidneys maintain balance.

21. Hyperkalemia and Hypokalemia

  • Hyperkalemia: High potassium, can cause cardiac arrhythmias

  • Hypokalemia: Low potassium, can cause muscle weakness

22. Chloride Functions

  • Maintains osmotic pressure, acid-base balance, stomach acid production.

23. Chloride Homeostasis Mechanisms

  • Follows sodium; regulated through renal mechanisms.

24. Hyperchloremia and Hypochloremia

  • Hyperchloremia: High chloride, can cause acidosis

  • Hypochloremia: Low chloride, can cause alkalosis

25. Calcium Functions

  • Bone structure, blood clotting, muscle contraction, nerve signaling.

26. Calcium Homeostasis Mechanisms

  • Regulated by parathyroid hormone (PTH), calcitonin, vitamin D.

27. Hypercalcemia and Hypocalcemia

  • Hypercalcemia: Can cause muscle weakness, kidney stones

  • Hypocalcemia: Can lead to muscle spasms, cardiac issues

28. Phosphate Functions

  • Bone structure, ATP formation, buffering systems.

29. Phosphate Homeostasis Mechanisms

  • Regulated by PTH, which increases excretion; reabsorption by kidneys.

30. Normal ECF pH Range

  • 7.35–7.45

31. Acids and Bases

  • Acids: Donate H⁺ ions, lower pH

  • Bases: Accept H⁺ ions, raise pH

32. Buffers

  • Systems that resist changes in pH by neutralizing added acids or bases.

33. Physiological vs. Chemical Buffers

  • Physiological: Respiratory, renal

  • Chemical: Bicarbonate, phosphate, protein buffers

34. Bicarbonate, Phosphate, and Protein Buffers

  • Bicarbonate: Primary ECF buffer

  • Phosphate: Important in ICF and renal tubules

  • Protein: Major buffer in cells and plasma

35. Respiratory System and pH

  • Removes CO₂ to lower acidity; rapid response to pH changes.

36. Urinary System and pH Control

  • Excretes H⁺ or retains bicarbonate to balance pH; slower but powerful.

37. Acidosis and Alkalosis

  • Acidosis: Low pH (<7.35), depresses CNS function, risk of coma

  • Alkalosis: High pH (>7.45), overexcites nerves, can cause spasms