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WHAT IS THE DISTRIBUTION OF BODY FLUIDS?
TOTAL BODY WATER IS 50% TO 70% OF TOTAL BODY WEIGHT
TOTAL BODY WATER IS HIGHER WHEN BODY FAT IS LOW AND VISA VERSA
ICF IS CONTAINED WITHIN CELLS AND IS 2/3 OF TOTAL BODY WATER
ECF IS OUTSIDE THE CELLS AND IS 1/3 OF TOTAL BODY WATER AND IS SEPARATED INTO PLASMA AND INTERSITIAL FLUIDS BY CAPILLARY WALLS. PLASMA IS FLUID INSIDE BLOOD VESSLES AND IS SMALLER THAN INTERSTITIAL, WHICH BATHES THE CELLS.
INTERSTITIAL IS THE ULTRAFILTRATE OF PLASMA
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WHAT IS AN EQUIVALENT?
USED TO DESCRIBE THE AMOUNT OF CHARGED SOLUTE AND IS THE NUMBER OF MOLES OF THE SOLUTE MULTIPLIED BY ITS VALENCE
1 mol KCl --> 1 K(+) and 1 Cl(-)
1 mol CaCl2 --> 2 Ca(2+) and 2 Cl(-)
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WHAT IS AN OSMOLE?
NUMBER OF PARTICLES INTO WHICH A SOLUTE DISSOCIATES IN SOLUTION
OSMOLARITY IS THE CONCENTRATION OF PARTICLES IN SOLUTION EXPRESSED AS OSMOLES/LITER
IF SOLUTE DISSOCIATES INTO MORE THAN ONE PARTICLE (NaCl) THEN ITS OSMOLARITY EQUALS THE MOLARITY MULTIPLIED BY THE NUMBER OF PARTICLES.
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WHAT IS THE COMPOSITION OF IONS IN ICF AND ECF?
K(+) AND Mg(2+) CATIONS BALANCED BY PROTEIN AND ORGANIC PHOSPHATE ANIONS IN ICF
Na(+) CATIONS BALANCED BY Cl(-) AND BICARBONATE ANIONS IN ECF
- ------ECF ICF mM
- Na+ 145 15
- K+ 4.5 120
- Cl- 116 20
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WHAT IS THE VOLUME OF BODY FLUID IN BLOOD, ECF, ICF, AND TRANSCELLULAR?
- BLOOD 3L
- ECF 13L
- ICF 25L
- TRANS 1L
- TOTAL 45L
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Stokes-Einstein relation and how various factors (parameters) can influence the diffusion coefficient.
D=KT/6πrη
- i. D = diffusion coefficient
- ii. K = Boltzmann’s constant
- iii. T = Absolute temperature
- iv. r = molecular radius
- v. η = viscosity of the medium
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WHAT IS OSMOSIS?
- water movement across lipid bilayers and membranes from area of high water concentration (low solute) to an area of low water
- concentration (high solute)
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WHAT IS OSMOTIC PRESSURE?
The pressure required to prevent the flow of water (osmosis).
Dependent on the concentration of osmotically active particles and whether or not they can cross the membrane.
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VAN'T HOFF'S LAW?
Allows you to calculate the osmotic pressure
Π=gCσRT
- 1. Π = osmotic pressure (atm)
- 2. g = particles per mole in solution (Osm/L)
- 3. C = concentration (mmol/L)
- 4. σ = reflection coefficient (0 to 1; 1 = impermeable)
- 5. R = gas constant
- 6. T = absolute temperature
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State differences between permeant and impermeant solutes and explain how this leads to the different definitions of osmolarity and tonicity.
- A. Permeant solute = solute that can go through the membrane (e.g. urea, reflection coefficient = 0)
- i. Produce transient changes in cell volume
- ii. If water is moving faster, there is initial change in volume, but then as permeant solute redistributes, water might move back.
- iii. The greater the membrane permeability to the permeant solute, the more rapid the time course of the transient volume changes
B. Impermeant solutes = solute that cannot go through the membrane (e.g. sugar, reflection coefficient = 1)
- C. Osmolarity = effective gradient for water assuming all the solute is completely impermeant
- i. Assumes all solute is impermeant.
- D. Tonicity = the tendency of a solution to resist expansion of the intracellular volume. Sometimes referred to as “effective osmolarity.”
- i. Takes into account permeant solutes.
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WHAT IS THE GIBBS-DONNAN EQUILIBRIUM?
- Gibbs-Donnan Equilibrium – plasma contains impermeable negative chares that leads to a redistribution of permeant anions (Cl-) and cations (Na+).
- i. A situation where anions/cations are freely permeable
Total charge is equal, but the concentration is asymmetric because of impermeant negative charges in the plasma.
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KNOW ABOUT THE ANION GAP AND HOW IT IS CALCULATED
Anion gap = an ‘artificial’ and calculated measure that is representative of the unmeasured ions in plasma and serum
Anion Gap plasma = [Na+]plasma – ([Cl-]plasma + [HCO3-]plasma)
Normal anion gap = 9-14 mEq/liter
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WHAT IS FACILITATED DIFFUSION?
MOVEMENT DOWN AN ELECTROCHEMICAL CONCENTRATION GRADIENT
CARRIER MEDIATED TRANSPORT
DOES NOT REQUIRE ATP
eg ION CHANNELS
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WHAT IS PRIMARY ACTIVE TRANSPORT?
(aka P-type or E1-E2 ATPases)
- 1. Substances move against electrochemical gradient
- 2. Requires directly coupled ATP (energy source)
- 3. eg Na-K ATPase Keeps high K inside and high Na outside. ATP. 3 Na out, 2 K in
- 4. eg H-K pump
- 5. eg Ca2+ Pump
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WHAT IS SECONDARY ACTIVE TRANSPORT?
Substances move against electrochemical gradient
- 1. Requires INDIRECTLY coupled ATP (derives energy from downhill movement of another substance)
- 2. eg Na-Ca Exchanger derives movement from downhill movement of Na
- 3. eg Na-H exchanger
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What is the importance of the asymmetrical distribution of components in the apical and basolateral membranes of polarized cells
There are different substances on apical versus basolateral sides, so there need to be different transport proteins
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GLUCOSE ABSORPTION
Na-K pump pumps Na out of cell (to keep intracellular Na low) and pumps K into the cell. (basolateral membrane)
Na and Glucose cotransport into the cell via SGLT on apical membrane
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WHY IS TRANSEPITHELIAL VOLTAGE IMPORTANT?
Transepithelial voltage drives paracellular movement across the epithelium
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WHAT HAPPENS IN SECRATORY DIARRHEA?
Cholera Toxin can constitiatively activate CFTR. If Cl is constantly moving into the lumen, so is water and Na is constantly following. SO you get intense diarrhea.
ORT – give them water, sugar, and salt.
Moving sugar across the gut is a Na dependent process so you move Na back into the basolateral side (rather than the lumen). Cl and water follow.
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What is the role of CFTR in the airway, pancreas, and sweat glands and the results of disrupting its function in these particular systems?
CFTR = protein dysfunctional in people with CF. An ABC transporter (regulated chloride transporter)
Sweat gland:
CFTR is responsible for the reabsorption of Cl in sweat
Elimination = no reabsorption
Cl builds up in lumen and Na builds up as well (to maintain charge)
VERY SALTY SWEAT
Pancreas
An exchanger normally moves bicarbonate OUT of the cell into the lumen and Chloride INTO the cell (antiporter)
CFTR moves chloride out of the cell (creating a low concentration of Cl in the cell so the bicarbonate/Cl exchanger can work)
Elimination = no chloride movement so Cl is low in the lumen
ALSO no movement of Na and H2O across
HIGHLY VISCOUS NON-BICARB RICH SOLUTION. Impairs digestive enzyme release. Bad. But not lethal.
Airway
Normally you want to keep mucous in the lumen. SO CFTR moves Cl into the lumen and Na and H2O follow.
If you don’t have CFTR, Cl is not secreted. The result is a reabsorption of water (instead of secretion) and you end up moving H2O and Cl in the opposite
direction.
This results in a highly viscous liquid on the epithelium which impairs cilia and gas exchange. Thus it increases the likelihood of bacterial infection.
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