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Phys3 Body water
Question | Answer |
---|---|
Total body water | Intracellular water (ICF) + Extracellular water (ECF). **Usually around 42L, 60% of body weight. |
Extracellular water/Fluid (ECF) | Interstitial fluid & lymph water + Plasma water. **14 L, 20% of body weight. |
Interstitial and lymph water | Combines with plasma water to make up ECF. **10.5L, 15% of body weight. |
Plasma Water | combines with intersitial fluid to form ECF. **3.5L, 5% of body weight. |
What is the osmolality of the BL plasma water, interstitial fluid, and ICF respectively? | 290mM!! for ALL 3. |
Where is Transcellular fluid found. | It is included in ECF, it is the fluid surrounded by epithelial cells. Found: 1.synovium w/in joints. 2.CSF. **1L, can exchange with interstitial fluid. |
What all does Blood Volume include? | 1.Plasma water (3L). 2.Formed elements (2.5L). **5.5L of BL within the INTRAVASCULAR system |
What is known as the transit region between BL and the cells? | Interstitial fluid (10.5L) |
Important Fluid barriers | 1.Cell membrane (seperates intracellular from interstitium). 2.Capillary walls (seperates intravascular compartment from interstitium). **there is an extra epithelial layer in addition to endothelium seperating transcellular compartment. |
Major cation of ICF | K+ |
Major cation & anions of ECF | 1.Na+ 2.Cl- & HCO3- |
Is interstial fluid or transcellular fluid considered ultrafiltrate of plasma? | INTERSTITIAL!! Same as plasma MINUS the proteins and cells. |
Steps of Indicator dilution method | 1.indicator that is confined to compartment of interest is injected. 2.Equilibration occurs throughout compartment. 3.plasma sample collected and concentration of indicator measured. 4.Vd is then deteremined. |
Equations for concentration and volume based on mass? | C=M/V. V=M/c |
equation for Volume of distribution (Vd) | Vd=(Mass of indicator injected - Mass of indicator lost)/Concentration in plasma. **Mass of indicator lost= Urine Volume x Concentration of indicator in urine. |
Indicators for total body water | 1.Antipyrine. 2.deuterium (D2O). 3.HTO. **will produce a fluid volume or Vd of ~42L |
Indicators for Plasma water | 1.Evan's Blue. 2.I-Albumin. **will produce a fluid volume or Vd of ~3L |
Indicators for ECF | 1.Impermeate ions (Na, Cl, sulfate, SO4, thiocyanate & thiosulfate). 2.Inert sugars (Inulin, mannitol, sucrose). **Inert sugars tend to underestimate total body water. **will produce a fluid volume or Vd of ~14L |
What does Osmolality refer to? | the # of osmotically active particles in a solution. |
Do most electrolytes move freely across the cell membrane? | NO. **K+ is major intracellular, Na+ is major extracellular |
Hypertonic osmolality | has a higher osmolality which will encourage water to move into it. **causing cell swelling. |
Hypotonic osmolality | Has a lower osmolality which will encourage water to move out of it. **causing cell shrinkage |
What 2 things determine a compartment's volume and osmolality? | 1.Compartmental solutes. 2.free movement of water. |
Volume expansion Vs. Volume contraction | Expansion: Increased ECF volume. Contraction: Decreased volume ECF. |
Isosmotic volume contraction or expansion | The volume changes without a change in osmolality. |
Hyperosmotic volume contraction or expansion | Volume changes due to an increase in osmolality. |
Hyposmotic volume contraction or expansion | Volume changes due to a decrease in osmolality. |
Expansion and contraction are used to describe what compartment? | ECF |
Addition of isotonic saline solution (isotonic NaCl) to ECF | 1.ICF osmolality:Same (290). 2.ECF osmolality:Same (290). 3.ICF volume:same. 4.ECF volume: Isosmotic volume expansion |
Removal of isosmotic fluid from ECF | 1.ICF osmolality:same (290). 2.ECF osmolality:same (290). 3.ICF volume:same. 4.ECF volume: Isosmotic volume contraction. **Diarrhea** |
Addition of pure water(or any hypotonic solution) to ECF | 1.ICF osmolality: <290. 2.ECF osmolality: <290. 3.ICF volume: Increases more than ECF. 4.ECF volume: Hyposmotic volume expansion. **seen in SIADH** |
Addition of NaCl (or any hypertonic solution) to ECF | 1.ICF osmolality:>290. 2.ECF osmolality:>290. 3.ICF volume: decreases. 4.ECF volume: Hyperosmotic volume expansion. |
Addition/Removal of Na+ will mainly affect the volume of what compartment? | ECF |
Addition/Removal of water will mainly affect the osmolality of what compartment? | Both. |
What will happen in water deprivation, sweating, and fever? | Hyperosmotic volume contraction. **Will lose more WATER than Na+. Osmolality of both are >290mM, Volume of ECF and ICF decrease. |
What will happen in Adrenal insufficiency? | Hyposmotic volume contraction. Osmolality of both are <290mM, Volume of ECF decreases while ICF increases. **Will lose more Na+ than water. |
Adrenal Insufficiency | 1.Dec Aldosterone production/release. 2.Leads to Dec Na+ reabsorption. 3.causes hyposmotic volume contraction. **causes a loss of water and Na+, but MORE Na+ than water. |
Type 1 Syndrome of inappropriate ADH secretion (SIADH) | 1.Secreting too much ADH. 2.leads to water reabsorption. 3.Hyposmotic volume expansion. **same as adding pure water to ECF. **Type 3 SIADH is euvolumic |
What two things cause Euvolemic changes? | 1.Diabetes insipidus. 2.SIADH. |
Effects on Hct and serum [Na+]: Isosmotic expansion | 1.Hct: Dec. 2.serum [Na+]: same. |
Effects on Hct and serum [Na+]: Isosmotic contraction | 1.Hct:Inc. 2.serum [Na+]:same. |
Effects on Hct and serum [Na+]: Hyperosmotic expansion | 1.Hct:Dec. 2.serum [Na+]: Inc. |
Effects on Hct and serum [Na+]: Hyperosmotic contraction | 1.Hct: same. 2.serum [Na+]: Inc. |
Effects on Hct and serum [Na+]: Hyposmotic expansion | 1.Hct: same. 2.serum [Na+]: Dec. |
Effects on Hct and serum [Na+]: Hyposmotic contraction | 1.Hct: Inc. 2.serum [Na+]: Dec. |
Improtance and maintenance of ECF volume? | *Critical for maintaining BP and perfusion. *maintained by monitoring and adjusting total body NaCl content |
How is ECF osmolality maintained? | by monitoring and adjusting total-body water content. |
What is the signal for Na+ homeostasis? | VOLUME!! |
Response to Dec BV/ECF | 1.Inc RAAS. 2.INC SNS outflow. 3.INC AVP/ADH. 4.DEC ANP. **Dec Na+ EXCRETION and Inc water Reabsorption |
How would an INC in osmolality affect the hypothalamus? | Osmoreceptors would trigger release of AVP/ADH to cause reabsorption of water. |
Response to Inc BV/ECF | 1.Inc Na+ excretion. 2.Dec water reabsorption. |