Body Water Compartments and Balance
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Questions and Answers

What is the primary cation found in extracellular fluid?

  • Potassium
  • Calcium
  • Magnesium
  • Sodium (correct)

    • Which of the following body tissues has the highest percentage of water?

  • Adult female
  • Infants (correct)
  • Skeletal muscle
  • Adipose tissue

    • What happens to cells when extracellular fluid osmotic pressure rises due to dehydration?

  • Cells burst
  • Cells shrink (correct)
  • Cells remain unchanged
  • Cells swell

    • How is excess water elimination initiated after water ingestion?

    <p>Kidneys eliminate excess after 30 minutes.</p> Signup and view all the answers

    Which condition leads to cell swelling due to hyponatremia?

    <p>Hypotonic hydration</p> Signup and view all the answers

    What is the major ion that dissociates into charged particles in water and conducts an electrical current?

    <p>Potassium</p> Signup and view all the answers

    Which hormone is primarily responsible for regulating the reabsorption of water in the kidneys?

    <p>Vasopressin (ADH)</p> Signup and view all the answers

    What factor stimulates the release of ADH?

    <p>Small rise in ECF osmolality</p> Signup and view all the answers

    What is the average total body fluid (water) volume for adults?

    <p>40 L</p> Signup and view all the answers

    Which of the following constitutes the largest mass of dissolved solutes in the body fluids?

    <p>Proteins</p> Signup and view all the answers

    What is the primary process in the kidneys for regulating acid-base balance during acidosis?

    <p>Reabsorption of bicarbonate and secretion of H+</p> Signup and view all the answers

    Which mechanism is most significant for excreting acid in the kidneys?

    <p>Excretion of ammonium ions produced from glutamine metabolism</p> Signup and view all the answers

    What indicates respiratory acidosis in blood gas analysis?

    <p>Blood pH below 7.35 and CO2 above 45 mm Hg</p> Signup and view all the answers

    Which condition can lead to metabolic alkalosis?

    <p>Vomiting acidic stomach contents</p> Signup and view all the answers

    How do the lungs compensate during metabolic acidosis?

    <p>By increasing ventilation to expel CO2</p> Signup and view all the answers

    What is a consequence of blood pH falling below 6.8?

    <p>Depression of the CNS leading to coma</p> Signup and view all the answers

    What does the term 'renal compensation' refer to?

    <p>Kidneys adjusting bicarbonate levels in response to respiratory imbalances</p> Signup and view all the answers

    Which of the following statements about infants and acid-base balance is correct?

    <p>Infants possess relatively more extracellular fluid compared to adults.</p> Signup and view all the answers

    What role do type B intercalated cells perform in alkaline conditions?

    <p>Secrete bicarbonate while reabsorbing H+ ions</p> Signup and view all the answers

    What is a key differentiator between respiratory and metabolic acid-base imbalances?

    <p>Metabolic imbalances can result from gastrointestinal losses</p> Signup and view all the answers

    What primarily causes edema in tissues?

    <p>Increased interstitial fluid volume</p> Signup and view all the answers

    Which hormone plays the most significant role in regulating sodium balance?

    <p>Aldosterone</p> Signup and view all the answers

    What effect does hyperkalemia have on the resting membrane potential of excitable cells?

    <p>It causes depolarization</p> Signup and view all the answers

    In which part of the nephron is the majority of filtered sodium reabsorbed?

    <p>Proximal convoluted tubule (PCT)</p> Signup and view all the answers

    Which factor primarily stimulates the secretion of aldosterone in the adrenal cortex?

    <p>Increased potassium levels in ECF</p> Signup and view all the answers

    What is the main role of atrial natriuretic peptide (ANP)?

    <p>Decreases blood volume and pressure</p> Signup and view all the answers

    What is the primary regulator of potassium secretion in the kidneys?

    <p>ECF potassium levels</p> Signup and view all the answers

    What condition is characterized by a deficiency in aldosterone production leading to sodium loss?

    <p>Addison's disease</p> Signup and view all the answers

    Which hormone causes mild diuresis as part of its physiological role?

    <p>Progesterone</p> Signup and view all the answers

    What effect does parathyroid hormone (PTH) have on the kidneys?

    <p>Increases calcium reabsorption</p> Signup and view all the answers

    What occurs in the body when extracellular potassium levels fall?

    <p>Membrane potential becomes more negative</p> Signup and view all the answers

    What occurs during hypocalcemia in the body?

    <p>Increased neuromuscular excitability</p> Signup and view all the answers

    Which of the following best describes the condition known as alkalemia?

    <p>Arterial pH &gt; 7.45</p> Signup and view all the answers

    How do chemical buffers respond to a strong base being added to a solution?

    <p>They release H+ to raise pH.</p> Signup and view all the answers

    What happens to respiratory function when there is a rise in arterial co2 levels?

    <p>Ventilation increases to expel excess carbon dioxide.</p> Signup and view all the answers

    Which buffer system operates primarily in intracellular fluid?

    <p>Protein buffer system</p> Signup and view all the answers

    During respiratory acidosis, what typically occurs in the body?

    <p>Carbon dioxide accumulates in the blood</p> Signup and view all the answers

    What role do the kidneys play in the regulation of bicarbonate?

    <p>They adjust bicarbonate levels by reabsorbing or excreting.</p> Signup and view all the answers

    What mechanism is responsible for the immediate response to acid-base imbalances?

    <p>Chemical buffers</p> Signup and view all the answers

    How is chloride predominantly reabsorbed in the kidneys?

    <p>Passively in the PCT, coupled with sodium transport</p> Signup and view all the answers

    Study Notes

    Body Water Compartments and Balance

    • Total Body Water (TBW): Varies with age, body mass, and fat percentage. Infants have 73% water, adult males ~60%, and adult females ~50%. Muscle is ~75% water, while fat is less than 20%. Average adult TBW is 40 liters.

    • Fluid Compartments: TBW is divided into intracellular fluid (ICF, ~2/3, 25L) and extracellular fluid (ECF, ~1/3, 15L).

      • ECF: Further divided into plasma (3L, part of blood) and interstitial fluid (IF, filling spaces between cells, ~12L). Other ECF components include lymph, CSF, eye humors, synovial fluid, serous fluid, and GI secretions.

    Body Solutes

    • Solutes: Water dissolves electrolytes and non-electrolytes.

      • Non-electrolytes: Do not dissociate into ions in water. Examples include glucose, lipids, creatinine, and urea.

      • Electrolytes: Dissociate into ions in water, conducting electricity. Examples include inorganic salts, acids, bases, and some proteins. Electrolytes have a greater osmotic power than non-electrolytes, affecting fluid shifts. Concentrations are measured in milliequivalents per liter (mEq/L). For single charge ions, 1 mEq is equal to 1 mOsm, for bivalent ions, 1 mEq is equal to 0.5 mOsm.

    • ECF vs. ICF: Key differences in ion concentrations. ECF has high Na+ and low K+, while ICF has high K+ and low Na+. ECF contains more chloride than ICF. ICF contains more proteins.

    Water Intake and Output

    • Water Balance: Intake must equal output (approximately 2500 mL/day).

      • Intake: Primarily from ingested food (~750 mL) and beverages (~1500 mL). A small amount is produced metabolically (~250 mL/day).

      • Output:

        • Insensible: Loss through skin and airways (~700 mL).
        • Sensible: Mostly urine (~1500 mL), sweat (~200 mL), and feces (~100 mL). Obligatory daily water loss through urine is essential for waste removal.

    Water Regulation

    • Osmolality: Normally maintained around 280-300 mOsm. Increased osmolality triggers thirst and ADH release. Decreased osmolality inhibits thirst and ADH release.

    • Thirst Mechanism: Controlled by hypothalamic thirst centers, stimulated by:

      • Osmoreceptors
      • Dry mouth
      • Decreased blood volume/pressure (via angiotensin II or baroreceptors)

    • ADH Regulation: Regulates water reabsorption in collecting ducts. Higher ADH leads to concentrated urine; lower ADH leads to diluted urine. ADH release is stimulated by:

      • Elevated ECF osmolality
      • Decreased blood volume/pressure (via baroreceptors and renin-angiotensin-aldosterone system)

    Fluid and Electrolyte Disorders

    • Dehydration: ECF fluid loss. Symptoms include thirst, dry mouth, dry skin, reduced urine output, weight loss, and confusion.
    • Hypotonic Hydration: Overhydration, often with renal insufficiency or excessive water intake. Symptoms include swelling of cells, hyponatremia, nausea, vomiting, muscle cramps, and cerebral edema.
    • Edema: Accumulation of interstitial fluid, causing tissue swelling. Not a change to intracellular fluid volume.

    Electrolyte Balance

    • Sodium (Na+): Most abundant ECF cation, crucial for maintaining ECF volume and water distribution.
    • Potassium (K+): Most abundant ICF cation, crucial for nerve and muscle function, resting membrane potential.
    • Calcium (Ca2+): Primarily in bones, regulated by parathyroid hormone (PTH), essential for blood clotting, cell membrane permeability, and neuromuscular function.
    • Chloride (Cl-): Major anion accompanying sodium in ECF, important for osmotic pressure.

    Acid-Base Balance

    • pH: Normal arterial blood pH is 7.4. ACIDOSIS(pH<7.35) and ALKALOSIS(pH>7.45) disrupt cellular functions.
    • Buffers: Prevent rapid changes in pH through chemical reactions. Major buffer systems include bicarbonate, phosphate, and protein systems.
    • Respiratory Regulation: Lungs eliminate carbon dioxide (a volatile acid), influencing pH.
    • Renal Regulation: Kidneys excrete or retain H+ and bicarbonate ions to maintain pH balance.

    Disorders and Compensation

    • Respiratory Acidosis/Alkalosis: Caused by imbalances in CO2 elimination. Lungs regulate via ventilation adjustments, while kidneys compensate for a long-term problem.
    • Metabolic Acidosis/Alkalosis: Caused by imbalances in non-volatile acids. Kidneys regulate via bicarbonate reabsorption or excretion, while lungs compensate for a short-term problem.

    Development Aspects

    • Infants: Have disproportionately more interstitial fluid, experience higher fluid intake, output and metabolic rates, and have less developed kidney function, making them more susceptible to dehydration and acid-base imbalances.

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    Description

    Explore the intricate details of body water compartments and their importance in maintaining fluid balance. This quiz covers total body water, fluid compartments, and the role of solutes, including electrolytes and non-electrolytes. Test your knowledge on how water is distributed in the body and the significance of different fluid types.

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