Physiology: Fluids
Which Solute is the most sensitive to change in concentration
Calcium As such calcium influx or efflux is an important switch to turn intracellular processes on/off (e.g. muscle contraction)!
Water content difference in men and women
Males have a higher water (50-65%) content than females (45-60%)
Extracellular Fluid maker substances
Mannitol Inulin- a starch commonly obtained by soaking chicory roots in hot water. Radioactive sulfate
What occurs in Hyposmotic Volume Contraction
Osmolarity in ECF: decreases solute concentration: decreases ECF: decreases ICF: increases Water is lost example of when this happens is Adrenal Insufficiency
What occurs in Hyposmotic Volume Expansion.
Osmolarity in ECF: decreases solute concentration: decreases ECF: increases ICF: increases Water is gained example of when this happens is SIADH
What occurs in Hyperosmotic Volume Contraction?
Osmolarity in ECF: increases solute concentration: increases ECF: decreases ICF: decreases Water is lost example of when this happens is sweating, fever, diabetes insipidus
What occurs in Hyperosmotic Volume Expansion.
Osmolarity in ECF: increases solute concentration: increases ECF: increases ICF: decreases Water is gained example of when this happens is high NaCl intake
What occurs in Isotonic Volumetric Contraction?
Osmolarity in ECF: no change solute concentration: no change ECF: decreases ICF: no change Water is lost example of when this happens is diarrhea
What occurs in Isotonic Volumetric Expansion?
Osmolarity in ECF: no change solute concentration: no change ECF: increases ICF: no change Water is gained example of when this happens is infusion of isotonic NaCl
What is osmolarity used for
Osmolarity: change in Solvent = change in H20 measures state of hydration used to monitor changes in body water (solvent) concentration. Units of mOsm/L or osmol/L are used. Since the total volume must always be 1L, the amount of water (solvent) decreases as the amount of solute increases the total volume is always 1L (solution) but the relative amounts of solute and solvent change inversely. As the amount of solute increases, the volume of solvent must decrease. As such, osmolarity is used to monitor changes in solvent (body water). It is a good measure of fluid volume as mOsm/L.
What is the Intracellualr Fluid?
compartment is the system that includes all fluid enclosed in cells by their plasma membranes.
What is the relationship between the ECF and ICF concentrations of solutes
inverse relationship
What is the Extracellular Fluid?
surrounds all cells in the body. Extracellular fluid has two primary constituents: •the fluid component of the blood (plasma: ¼ ECF) •interstitial fluid (IF: ¾ ECF) that surrounds all cells not in the blood.
A 70 kg male is injected with 1.5 g of mannitol. During the equilibration period, 5% of the mannitol was excreted/hour. After two hours of equilibration, the plasma concentration of mannitol was measured as 9 mg/100 ml. What body fluid compartment is being measured, and what is its volume (i.e., what is the volume of distribution of mannitol)? Is this a reasonable number?
Volume = (1500 mg- 150 mg)/ (9mg/100ml) Volume = 1350 mg/ 90 mg/L Volume = 15 L (volume of distribution of mannitol, or ECF volume)
What is Adrenal Insufficiency (Addison's Disease)
a condition in which the adrenal glands do not produce adequate amounts of steroid hormones, primarily cortisol; but may also include impaired production of aldosterone (a mineralocorticoid), which regulates sodium conservation, potassium secretion, and water retention. a concentrated (hyperosmotic) urine, high in Na+ ions, is produced (\crave salt). ECF ion loss leaves it hypoosmotic. Since ECF is hypoosmotic to the ICF, water moves osmotically to expand the ICF volume.
What is Osmolality?
a variation of molality that takes into account only solutes that contribute to a solution's osmotic pressure. It is measured in osmoles of the solute per kilogram of water (osmol/kg or Osm/kg).
What is Osmolarity and what is it used for?
(osmotic concentration) is the measure of solute concentration, defined as the number of osmoles (Osm) of solute per litre (L) of solution (osmol/L or Osm/L). 1 mol/L NaCl yields 2 osmol/L
Describe the continuous fluid flow through the body.
1. Intracellular fluid (ICF) to Interstitial fluid (ECF) 2. Blood Plasma to interstitial fluid (ECF) 3. ECF to Lymphatic Fluid 4. Lymph back to Blood
What cells produce CSF and what is the normal volume in the body
20% CSF is produced by ependymal cells present in the brain ventricles at a rate of 20 ml/h. In normal adults, the CSF volume is 125 to 150 ml.
Human percent variation of water
50-70%
What is the 60-40-20 rule?
60% of body wight is total body water (TBW) of that 60%, 40% is intercellular fluid (ICF) of that 60%, 20% is extracellular fluid (ECF)
what is the significance of Avogadro's number
Avogadro's Number, 6.02214076 × 10^23, is the number of units / particles in one mole of any substance
Total body water maker substances
D2O- heavy water made with deuterium HTO- tritiated water Antipyrene- analgesic and antipyretic given by mouth or as ear drops
what is Syndrome of Inappropriate Antidiuretic Hormone (SIADH)
Inappropriate production of ADH prevents fluid excretion so both the ECF and ICF compartments continue to gain water, or expand SI-ADH is also defined by hyponatremia. Hyponatremia results from an excess of water rather than a deficiency of sodium
Most of the water in the body is...
Intracellular fluid
Why do men have higher water content?
Men have a higher water content because of their greater muscle mass (76% water).
A man with a: TBW of 40 L, ICF volume of 26.4 L, ECF volume of 13.6 L, and plasma osmolarity of 290 mOsm/L drinks 3 L of water. what is the new total body water osmolarity?
Old TBW osmoles = 40 L x 290 mOsm/L = 11,600 mOsm •New TBW = 40 L + 3 L = 43 L •New TBW osmolarity = 11,600 mosmoles/43 L = 269.8 mOsm/L
What is osmolality used for
Osmolality: change in Solute = change Electrolytes to measure ionic balance the amount of water always remains constant at 1kg. So, as more solute is added, the osmolality increases since the total water volume (solvent) is constant (mOsm/kg). This is a good way to monitor changes in solute concentration.
Plasma maker substances
Radioiodinated serum albumin (RISA) Evan's blue
What is a solution?
Solution = Solvent + Solute Solvent is always water in the human body Solutes include electrolytes (electrically charged minerals) and transport proteins (carries lipids, carbohydrates, and electrolytes)
What is the definition of Osmosis
The movement of water from a region of low to high solute concentration through a semipermeable membrane.
What is Molality?
is the number of moles of solute dissolved in one kilogram of solvent. (mol/kg) •Molality uses mass rather than volume, •Molality uses solvent instead of solution, •Molality is independent of temperature (mass does not change with temperature).
what is Molarity?
is the number of moles of solute dissolved in one liter of solution (mol/L)
What happens to total body water as you get older?
it decreases By the age of 60 years, total body water has decreased (largely intracellular water) to only 50% of body weight in males. •Traditionally, this has been blamed on increases in adipose tissue with aging. This concept has recently been challenged.
A woman with an: ICF volume of 28 L, ECF volume of 14 L, and plasma osmolarity of 295 mOsm/L, eats a bag of potato chips that contains 300 mmoles of NaCl. What was gained or lost?
•Gain = 300 mmoles of NaCl = 600 mosmoles (300 x 2)
A man with a: TBW of 40 L, ICF volume of 26.4 L, ECF volume of 13.6 L, and plasma osmolarity of 290 mOsm/L drinks 3 L of water. What is the new ECF?
•Old ECF osmoles = 13.6 L x 290 mOsmles/L = 3944 mOsm •New ECF volume = 3944 mosmoles/ 269.8 mOsm/L = 14.6 L
A woman with an: ICF volume of 28 L, ECF volume of 14 L, and plasma osmolarity of 295 mOsm/L, eats a bag of potato chips that contains 300 mmoles of NaCl. What is the new ECF volume?
•Old ECF osmoles = 14 L x 295 mOsm/L = 4130 mOsm • New ECF osmoles = 4130 mOsm + 600 mOsm = 4730 mOsm •New ECF volume = 4730 mOsm/309.3 mOsm/L = 15.3 L
A man with a: TBW of 40 L, ICF volume of 26.4 L, ECF volume of 13.6 L, and plasma osmolarity of 290 mOsm/L drinks 3 L of water. what is the new ICF?
•Old ICF osmoles = 26.4 L x 290 mOsm/L = 7656 mOsm •New ICF volume = 7656 mOsm/269.8 mOsm/L = 28.4 L
A woman with an: ICF volume of 28 L, ECF volume of 14 L, and plasma osmolarity of 295 mOsm/L, eats a bag of potato chips that contains 300 mmoles of NaCl. What is the new ICF volume?
•Old ICF osmoles = 28 L x 295 mOsm/L = 8260 mOsm •New ICF volume = 8260 mOsm/309.3 mOsm/L = 26.7 L
A woman with an: ICF volume of 28 L, ECF volume of 14 L, and plasma osmolarity of 295 mOsm/L, eats a bag of potato chips that contains 300 mmoles of NaCl. What is the new total body weight osmolarity?
•Old TBW = 28 L + 14 L = 42 L •Old TBW osmoles = 42 L x 295 mOsm/L = 12,390 mOsm •New TBW osmoles = 12,390 mOsm + 600 mOsm = 12,990 mOsm New TBW osmolarity= 12,990 mOsm/42L = 309.3 mOsm/
What is transcellualr fluid (TCF)?
•TCF is an additional fluid compartment that is separated from other body fluids by a distinct layer of cells. •The collective volume of transcellular fluids is so small that they are ignored in calculating TBW. •TCF includes gastrointestinal, peritoneal, pleural, and cerebrospinal fluids (CSF).
Equation for measuring fluid compartment volumes
•Volume = (amount given - amount lost during equilibration) / concentration