Regulation of Solutes and Water in Body Fluid Compartments

Question 1

What is the role of the the Na-K pump?

Answer 1

Keeps [Na+] inside the cell low and [K+] high
Pumps 3 Na+ out and 2 K+ (electrogenic)
This pump is present everywhere
Contributes to creating negative voltage inside

Question 2

What is the role of the Ca-H pump and the Na-Ca exchanger?

Answer 2

Keep intracellular [Ca2+] four orders of magnitude lower than extracellular [Ca+]
Present on membranes that surround organelles like sarcoplasmic reticulum and ER

Question 3

What is the role of the Na+-H+ exchanger and the Na+ driven Cl-HCO3?

Answer 3

Keep intracellular pH and [HCO3-] above their equilibrium values

Question 4

What would happen in the result of low pH?

Answer 4

More H+ would be pumped inside the cell

Question 5

In most cells, why is [Cl-] moderately above equilibrium?

Answer 5

Cl- uptake via the Cl-HCO3 exchanger and Na/K/Cl cotransporter balances passive Cl- efflux through channels

Question 6

Long term control of Na+

Answer 6

By ingestion and urinary excretion

Question 7

Short term control of Na+

Answer 7

By the Antidiuretic hormone-thirst control system

Question 8

K+ regulation

Answer 8

By aldosterone

Question 9

Water transport and regulation of cell volume by:

Answer 9

Hydrostatic pressure (water)
Osmotic pressure (solute)
Oncotic pressure (albumen, liver)

Question 10

If cells are exposed to a hyperosmotic solution, they _____

Answer 10

Shrink and lose water

Question 11

If cells are exposed to a hyoosmotic solution they _____

Answer 11

Swell and gain water

Question 12

Cells activate volume regulatory mechanisms in response to _________

Answer 12

Volume perturbations

Question 13

Regulatory volume decrease (RVD)

Answer 13

Volume regulatory solute loss

Question 14

Regulatory volume increase (RVI)

Answer 14

Volume regulatory solute gain

Question 15

_______ is essential to regulate cell volume

Answer 15

Na-K pump

Question 16

How is osmotic equilibrium maintained?

Answer 16

By an equal number of positive and negative ions moving in and out of the cell

Question 17

What happens after inhibition of the Na-K pump with ouabain?

Answer 17

Continues passive leakage disrupts the osmotic equilibrium and water flows into the cell causing swelling

Question 18

What does the passive entry of 3 Na+ and efflux of 2 K+ result in?

Answer 18

1 more intracellular cation

Question 19

What happens when the Na-K pump is inhibited?

Answer 19

Intracellular K+ declines slowly, the cell depolarizes–> this allows Cl to enter the cells

Question 20

What is the driving force to keep Cl out of the cell?

Answer 20

The inside-negative voltage

Question 21

Filtration

Answer 21

1. Heart is pump, exerts hydrostatic pressure on blood
2. Tends to drive water out of capillaries
3. the net driving force= algebraic sum of oncotic pressure difference between capillaries and interstitial fluid

Question 22

Chronic Liver Disease

Answer 22

Liver produces most of the serum albumin
Serum albumin not produced sufficiently in liver disease
Oncotic pressure decreases
Fluid moves out of capillaries into the interstitial space (edema)

Question 23

Crystalloids

Answer 23

Solutes of low molecular weight constituting both electrolytes and non-electrolytes that can enter all body compartments
EX: lacated ringer’s, 5% dextrose, physiological saline

Question 24

5% glucose

Answer 24

Type of fluid
Isotonic but can enter the cell and is metabolized
Water remains and thus maintains volume
Provides calories

Question 25

Isotonic Saline (0.9% NaCl)

Answer 25

Will not alter the osmotic movement of electrolytes across membranes
Distributed evenly in the ECF

Question 26

Dextrose/ saline

Answer 26

Maintenance fluids

Question 27

Hypotonic Fluids

Answer 27

Lows osmotic pressure and causes water intoxication

Question 28

Hypertonic Fluids

Answer 28

Increases osmotic pressure and draws water from the cells and cause cellular dehydration

Question 29

Transport of solutes and water across epithelia

Answer 29

Transcellular and Paracellular

Question 30

Transcellular Transport

Answer 30

Sequentially passing through the apical and then the basolateral membranes or the opposite way

Question 31

Paracellular transport

Answer 31

Crosses the pithelium through the membrane junctions and lateral intercellular spaces (requires a pump)

Question 32

Na+ Absorption

Answer 32

Basolateral Na-K pumps Na out of the cell
Lowers Na –> inward Na electrochemical gradient across apical membrane
Na enters cell passively across apical membrane
The positive charge from lumen to interstitium creates a lumen negative transepithelial voltage that allows Cl- pass through tight junction

Question 33

K+ Secretion

Answer 33

Basolateral Na-K pump will pump K+ into the cell

K+ secreted through apical membrane

Question 34

Water transport

Answer 34

The intestinal epithelium can transport water in response to osmotic gradient
Passively flows solute transport- solute coupled transport