Fluid Compartments

Question 1

Suppose you have two chambers of water separated by a selectively permeable membrane. The chambers are labeled A and B respectively and initially the equal-sized chambers are both half-full with pure water. The membrane is permeable to water and sodium, but impermeable to potassium and chloride. What will happen with respect to net movement of water if chamber A suddenly has 100 mM potassium chloride? a) Water will shift from chamber A to chamber B. b) Water will shift from chamber B to chamber A. c) There will be no net movement of water. d) Potassium will diffuse from chamber A to chamber B.

Answer 1

b -

Question 2

Suppose a person is given a 1 liter intravenous infusion of isotonic NaCl solution. How much of this fluid will remain in the extracellular space? a) None b) About 1/3 c) About 2/3 d) All

Answer 2

d - all

Question 3

The sodium-potassium pump hydrolyzes one molecule of ATP each time it moves 3 sodium ions out of the cell and 2 potassium ions into the cell. What type of transport does this carrier protein perform? a) Simple diffusion b) Facilitated diffusion c) Primary active transport d) Secondary active transport

Answer 3

C - primary active transport

Primary active transport implies the direct consumption of metabolic energy (e.g., ATP hydrolysis). Secondary active transport implies a two component system – a primary active transporter that creates an ion gradient, and a co-transporter that exploits the gradient but does not directly utilize metabolic energy.

Question 4

Which body compartment has 2/3 of the body fluid at any given time: intra or extracellular?

Answer 4

intracellular

Question 5

What are the two divisions for extracellular fluid?

Answer 5

interstitial (75%) and plasma (25%)

Question 6

Which of the following solutes are high in extracellular fluid? Na cl glucose K Mg phosphate

Answer 6

Na, Cl, and glucose

Question 7

Which of the following are high in intracellular fluid? Na Cl Glucose K Mg Phosphate

Answer 7

K, Mg, Phosphate

Question 8

Does the intracellular or extracellular fluid have a higher protein concentration?

Answer 8

intracellular fluid

Question 9

What is the Donnan effect?

Answer 9

small differences in ionic composition of plasma and interstitial fluid attributed to the Donnan effect (also known as Gibbs-Donnan equilibrium). This effect arises because plasma proteins have a net negative charge but cannot leave the vascular compartment obligating a greater number of positively charged ions to remain in plasma and more negatively charged ions to stay in the interstitium.

Question 10

What are the two forces driving transport across a semi permeable membrane?

Answer 10

Diffusion pressure and membrane potential

Question 11

What is another word for diffusion pressure?

Answer 11

chemical gradient

Question 12

The net electrochemical gradient is a sum of what two forces driving transport?

Answer 12

Diffusion pressure/chemical gradient and membrane potential

Question 13

Define secondary active transport

Answer 13

When the potential energy stored in a chemical concentration gradient is used to drive transport of another ion

Question 14

How is facilitated diffusion different to passive transport?

Answer 14

facilitated diffusion is a special subclass of passive transport in which a simple transporter is involved in moving a solute down it’s concentration gradient (i.e. binds the thing and moves it, not just an open channel)

Question 15

How is urea transported (of the types of transportation learned in lecture?)

Answer 15

via facilitated diffusion

Question 16

What are the three broad categories of channels?

Answer 16

voltage gated ligand gated leak channels

Question 17

How are leak channels defined?

Answer 17

leak channels mediate passive movement of ions or water WITHOUT requiring stimulation by membrane potential or ligands (i.e. they are tonically open)

Question 18

What are the two broad types of ATPase pumps?

Answer 18

P type V type

Question 19

What are V type ATPase pumps?

Answer 19

vacuolar pumps for protons

Question 20

What is the difference between osmolality and osmolarity?

Answer 20

osmolality is osmoles (active solute molecule) per Kg of water while osmolarity is by LITER of water

Question 21

Why is osmolality preferred over osmolarity when discussing physiology?

Answer 21

volume changes with temperature of the body, but mass does not

Question 22

What is the osmole gap?

Answer 22

the different between measured and estimated Posm values that can point to accumulations of unmeasured osmoles such as ethanol

Question 23

A solution with higher osmolality than the interior of the cell is hypotonic or hypertonic?

Answer 23

hypertonic

Question 24

A cell in a hypertonic solution will: shrink or swell?

Answer 24

Shrink - driving force pushes water out of the cell to balance out the solutes there

Question 25

A cell in a hypotonic solution will: shrink or swell?

Answer 25

swell - water will go into the cell to balance out the osmoles inside the cell

Question 26

When does herniation of the brain occur in a setting of abnormal tonicity?

Answer 26

when the brain fluid is hypotonic compared to the cells, the cells will swell within the skull and press against the cranium

Question 27

How do you treat a brain herniation due to hypotonic extracellular fluid?

Answer 27

you administer IV osmotic active substances such as mannitol, which promotes water movement out of the cells and temporarily reverses brain swelling. Mannitol will not move into the cells and therefore is restricted to ECF

Question 28

What is a cellular short term response to hypotonic solution?

Answer 28

Cells exposed to hypotonic solution that begin to swell from passive water uptake will respond by releasing intracellular ions such as K and Cl such that the osmotic gradient is reduced and the direction of water movement is reversed. This is regulatory volume decrease

Question 29

What is regulatory volume decrease?

Answer 29

Cells exposed to hypotonic solution that begin to swell from passive water uptake will respond by releasing intracellular ions such as K and Cl such that the osmotic gradient is reduced and the direction of water movement is reversed.

Question 30

In hypertonic solution, what is the short term response of the cell to shrinkage?

Answer 30

In hypertonic solution when cells begin to shrink upon passive water loss, transport of Na, K and Cl will be activated to increase intracellular osmolality and promote water uptake. This is a regulatory volume increase.

Question 31

What is regulatory volume increase?

Answer 31

In hypertonic solution when cells begin to shrink upon passive water loss, transport of Na, K and Cl will be activated to increase intracellular osmolality and promote water uptake.

Question 32

What are idiogenic osmoles?

Answer 32

changes in osmotically active molecules as a long term response to hypo or hypertonic solutions - i.e. taurine, glycine, glutamine, sorbitol and inositol

Question 33

taurine, glycine, glutamine, sorbitol and inositol are all examples of what kind of molecules?

Answer 33

idiogenic osmoles, which are regulated as long term adaptations to hyper or hypotonic solution

Question 34

What effect will isoosmotic saline solution have on ECF and ICF?

Answer 34

only ECF volume will increase, osmolality will not change

Question 35

What effect will hypoosmotic saline have on ECF and ICF?

Answer 35

both ICF and ECF will increase, osmolality will be reduced overall

Question 36

What effect will hyperosmolar saline have on ECF and ICF?

Answer 36

expand ECF but reduce ICF due to increased osmolality of ECF

Question 37

Under severe conditions of fever, dry climate or hyperventilation, what happens to ECF and ICF?

Answer 37

dehydration via pure water loss - both ICF and ECF will decrease (2/3 from cells and 1/3 from EC) and osmolality of both will increase by equal magnitudes (although initially will occur more in EC, and this will pull water out of IC)

Question 38

Why is it important to know that the majority of pure water loss in “insensible” dehydration is occuring inside the cells?

Answer 38

The effect of pure water loss on plasma volume only represents one-twelfth of the total loss. For example, loss of 1 liter of pure water will result in only 83 ml reduction in plasma volume which is unlikely to cause a change in blood pressure. On the contrary, hypotension in the setting of pure dehydration signifies a profound degree of water loss.

Question 39

Define insensible water loss

Answer 39

pure water loss via evaporation and exhaled water vapor

Question 40

What effect will iso osmotic fluid loss have on ICF and ECF?

Answer 40

osmolality will not be impacted. ECF will decrease, causing a decrease in BP if severe

Question 41

What effect would excessive sweating, diarrhea, osmotic diuresis or GI/renal fluid loss have on ECF and ICF?

Answer 41

this is hypoosmotic fluid loss - reduced ECF at first without changes in osmolality. Loss of pure water will increase osmolality of both ICF and ECF, though not as severely as in cases of insensible pure water loss such as dehydration

Question 42

What is the relationship between loss of 1 liter of hypotonic fluid with an osmolality equal to one half of normal plasma and the corresponding change in BP?

Answer 42

For loss of 1 liter of hypotonic fluid that has an osmolality equal to one-half of normal plasma, extracellular volume will be reduced by 667 ml (500 ml of isoosmotic fluid, 167 ml of pure water [one third of 500 ml water]). The reduction in plasma volume will be 25% of the 500 ml of isoosmotic fluid plus one twelfth of the 500 ml water (or 41.6 ml) for a net reduction of 167 ml. ** exposure only ***

Question 43

What is the normal production of H+ in protein digestion?

Answer 43

1 mEq of H+ per Kg of body weight with normal dietary protein catabolism

Question 44

What is the waste management function of the kidneys?

Answer 44

elimination of phosphates and N wastes, elimination of H+

Question 45

What is the most important factor for regulating BP in the long terM?

Answer 45

maintaining proper balance of sodium secretion - Na is the main extracellular solute, so it determines the ECF volume

Question 46

To maintain a constant BP, what must be true of Na intake and excretion?

Answer 46

they must be equal

Question 47

What are the two main hormones produced by the kidney?

Answer 47

renin and erythropoeitin

Question 48

What two substances are enzymatically activated by the kidney?

Answer 48

vitamin D and angiotensin II

Question 49

Which hormones are the kidneys the target organs for?

Answer 49

aldosterone, ADH, PTH, and AnP

Question 50

What is the equation that can estimate plasma osmolality?

Answer 50