Keef 6 Flashcards
T/F The majority of our body weight is due to water. If true, what could change this?
True.
This could change if you become morbidly obese b/c then fat will make up a large portion of your body weight.
What is the equation for measuring the volume of a fluid compartment w/ a tracer?
Volume = Quantity of Tracer/Conc’n of Tracer
1 L of H20 is equal to how many kg of H20?
1
What tracer is usu used to measure total body water?
D20, heavy water
What tracer is usu used to measure total extracellular fluid?
sodium, iodine, inulin
What tracer is usu used to measure plasma volume?
I-albumin
What tracer is usu used to measure blood volume?
chromium labeled red blood cells.
Aside from using chromium labeled red blood cells, what is another way to measure the blood volume?
Plasma Volume (I-albumin)/1-Hct = Blood Volume
How do you find the volume of the interstitial fluid?
Interstitial Fluid = Extracellular Fluid - Plasma Volume
How do you measure intracellular fluid volume?
Total Body Volume - Extracellular Fluid Volume = Intracellular Fluid Volume
Approximately what percentage of your body weight is due to water?
60%
Approximately what percentage of your body weight is due to intracellular water?
40%
Approximately what percentage of your body weight is due to extracellular water?
20%
About how many liters of water is in your body?
~42 L
About how many liters of water is in your blood?
~3 L
Joe Cell is essentially a perfect ________. The exception to this is which organ?
osmometer: the fluid moves where it needs to!
Exception: brain b/c of the confines of the skull–but it has compensatory mechanisms.
When we talk about acidosis or over hydration…are we talking about outside of the cells or inside of the cells?
Outside of the cells. Extracellular fluid.
What does careless over-administration of saline cause? What does it do to the ECF & ICF compartment volumes? To osmolarity?
Isotonic Overhydration
ECF compartment expands in volume
ICF stays the same
same osmolarity
What does psychogenic polydipsia cause? What does it do to the ECF & ICF compartment volumes? To osmolarity?
Hypotonic Overhydration
ECF & ICF compartment volumes expand
Osmolarity decreases
What does drinking sea water cause? What does it do to the ECF & ICF compartment volumes? To osmolarity?
Hypertonic Overhydration
ECF expands; ICF shrinks
Osmolarity increases
**patient will experience increased thirst & edema
What does a hemorrhage do? What does it do to the ECF & ICF compartment volumes? To osmolarity?
Causes isotonic dehydration
ECF compartment shrinks
ICF remains constant
osmolarity remains constant
What does Addison’s Disease cause? What does it do to the ECF & ICF compartment volumes? To osmolarity?
This is due to adrenal insufficiency…you lose a bunch of super salty water b/c no aldosterone for salt reabsorption
Hypotonic Dehydration (ECF becomes hypotonic)
ECF compartment shrinks
ICF compartment expands
osmolarity decreases
What happens when you’re lost in the desert w/ no water & you sweat a lot? What does it do to the ECF & ICF compartment volumes? To osmolarity?
You lose water, w/o losing very much salt.
This increases the osmolarity of your ECF.
Your ECF volume decreases from sweating.
ICF shifts into ECF.
Ultimately…
ECF & ICF shrink in size
Osmolarity increases
What happens when you have Diabetes Insipidus?
What does it do to the ECF & ICF compartment volumes? To osmolarity?
You lack ADH…can’t reabsorb water properly…gives blood w/ high osmolarity. Triggers thirst.
You ultimately lose more water than you do salt.
This increases the osmolarity of your ECF.
Your ECF volume decreases from lack of ADH reabsorption.
ICF shifts into ECF.
Ultimately…
ECF & ICF shrink in size
Osmolarity increases
Extracellular sodium conc’n can remain normal in which 2 cases?
Isotonic Dehydration (hemorrhage) & Isotonic Overhydration (IV overadmin)
Extracellular sodium conc’n can decrease in which 2 cases?
Water intoxication (hypotonic overhydration) or Addison’s Disease (hypotonic dehydration)
Extracellular sodium conc’n can increase in which 2 cases?
Drinking sea water (hypertonic over hydration) or sweating w/o water in the desert (hypertonic dehydration).
2 cases of hypernatremia include drinking sea water & being lost in the desert…how would plasma proteins help you distinguish which of these 2 cases was actually happening?
Plasma proteins would be dilute if the person were drinking sea water…the sea water doesn’t have plasma proteins!!
Plasma proteins would be conc’nted if the person were sweating w/o water in the desert….b/c they’re not sweating out plasma proteins & they’re losing water.
If a person sweats out 2L of sweat & then drinks 2 L of water…what happens to their plasma osmolarity? Intracellular osmolarity?
B/c they sweat out salt & didn’t replace it…their osmolarity for both will decrease.
If a person sweats out 2L of sweat & then drinks 2 L of water…what happens to their ECF compartment?
It will actually decrease in volume b/c the hypotonic fluid will want to shift into the intracellular compartment where there are more solute particles.
If a person sweats out 2L of sweat & then drinks 2 L of water…what happens to their ICF compartment?
It will actually expand in volume b/c the hypotonic fluid that is replaced in the ECF will shift into the ICF where there is a greater conc’n of solute particles.
When you are sweating slowly what happens to…
the flow rate
the osmolarity of the sweat
the amount of salt reabsorption that takes place?
The flow rate is lower
this allows more sodium to be reabsorbed…
the osmolarity of the sweat is lower b/c there is less salt.
Hypotonic sweat w/ low salt
When you are sweating quickly what happens to…
the flow rate
the osmolarity of the sweat
the amount of salt reabsorption that takes place?
the flow rate is faster
this allows less time for sodium to be reabsorbed…
the osmolarity of the sweat is greater b/c there is more salt.
Hyptonic sweat STILL but w/ a higher amount of salt than if you were sweating slowly.
When you sweat a lot & then drink a lot of water…what is the conc’n of your sweat? What is your net loss?
You ALWAYS have hypotonic sweat. BUT you still lose salt.
Thus, your net loss is salt!
Losing salt from your body thru sweat & replacing only the water lost thru drinking water…is exactly the same fluid compartment story as what condition?
Addison’s Disease.
Lack of aldosterone…not the same salt reabsorption.
What is the equation for osmolar clearance?
Cosm = Uosm X V/Posm
**pt is to maintain Cosm if you have a hypertonic urine you will have a lower urine volume.
What is the equation for free water clearance?
V = Cosm + CH2O (free water)
When you have a dilute urine…what does that mean for your free water?
It will be positive.
When you have isotonic urine…what does that mean for your free water?
It will be zero.
Cosm = V
When you have hypertonic urine…what does that mean for your free water?
It will be negative.
**all the H2O is taken back up in the collecting duct b/c of ADH
During antidiuresis…where is free water created in the nephron? Where is hypertonic urine created?
Free water created in the thick ascending limb of the loop of Henle.
This water is reabsorbed in the collection duct b/c in antidiuresis ADH is present.
This creates a salty, hypertonic urine.
During diuresis…where is free water created in the nephron? Where is hypertonic urine created?
Free water is created in the thick ascending limb of the loop of Henle.
The urine never becomes hypertonic/salty b/c the free water is never reabsorbed. In diuresis, ADH isn’t present & aquaporins aren’t inserted into the collecting ducts.
What happens to the water that is reabsorbed in the collecting duct?
It goes into the interstitial space & is then reabsorbed into the bloodstream by the vasa recta (this is in the medullary region).
Which diuretic is potassium sparing? Why?
Amiloride.
It is located in the end of the DCT.
It is potassium sparing b/c it blocks sodium reabsorption. Potassium is exchanged & excreted out.
Which diuretic acts in the location where free water is created?
Furosemide.
It is located in the thick ascending limb of the loop of Henle.
How would the use of furosemide differ in its affects on V, Uosm, & CH2O when compared to thiazide?
Both would increase V.
Furosemide would increase Uosm more.
Furo would decrease CH2O significantly.
This is b/c furosemide works in the thick ascending limb of the loop of Henle. If the transporter here was blocked it would increase urine flow, but decrease sodium reabsorption & never give the nephron a chance to produce that free water. Thus, the urine will be more hypertonic.
