Regulation of Solutes and Water in Body Fluid Compartments Flashcards
What is the role of the the Na-K pump?
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
What is the role of the Ca-H pump and the Na-Ca exchanger?
Keep intracellular [Ca2+] four orders of magnitude lower than extracellular [Ca+]
Present on membranes that surround organelles like sarcoplasmic reticulum and ER
What is the role of the Na+-H+ exchanger and the Na+ driven Cl-HCO3?
Keep intracellular pH and [HCO3-] above their equilibrium values
What would happen in the result of low pH?
More H+ would be pumped inside the cell
In most cells, why is [Cl-] moderately above equilibrium?
Cl- uptake via the Cl-HCO3 exchanger and Na/K/Cl cotransporter balances passive Cl- efflux through channels
Long term control of Na+
By ingestion and urinary excretion
Short term control of Na+
By the Antidiuretic hormone-thirst control system
K+ regulation
By aldosterone
Water transport and regulation of cell volume by:
Hydrostatic pressure (water) Osmotic pressure (solute) Oncotic pressure (albumen, liver)
If cells are exposed to a hyperosmotic solution, they _____
Shrink and lose water
If cells are exposed to a hyoosmotic solution they _____
Swell and gain water
Cells activate volume regulatory mechanisms in response to _________
Volume perturbations
Regulatory volume decrease (RVD)
Volume regulatory solute loss
Regulatory volume increase (RVI)
Volume regulatory solute gain
_______ is essential to regulate cell volume
Na-K pump
How is osmotic equilibrium maintained?
By an equal number of positive and negative ions moving in and out of the cell
What happens after inhibition of the Na-K pump with ouabain?
Continues passive leakage disrupts the osmotic equilibrium and water flows into the cell causing swelling
What does the passive entry of 3 Na+ and efflux of 2 K+ result in?
1 more intracellular cation
What happens when the Na-K pump is inhibited?
Intracellular K+ declines slowly, the cell depolarizes–> this allows Cl to enter the cells
What is the driving force to keep Cl out of the cell?
The inside-negative voltage
Filtration
- Heart is pump, exerts hydrostatic pressure on blood
- Tends to drive water out of capillaries
- the net driving force= algebraic sum of oncotic pressure difference between capillaries and interstitial fluid
Chronic Liver Disease
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)
Crystalloids
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
5% glucose
Type of fluid
Isotonic but can enter the cell and is metabolized
Water remains and thus maintains volume
Provides calories
Isotonic Saline (0.9% NaCl)
Will not alter the osmotic movement of electrolytes across membranes
Distributed evenly in the ECF
Dextrose/ saline
Maintenance fluids
Hypotonic Fluids
Lows osmotic pressure and causes water intoxication
Hypertonic Fluids
Increases osmotic pressure and draws water from the cells and cause cellular dehydration
Transport of solutes and water across epithelia
Transcellular and Paracellular
Transcellular Transport
Sequentially passing through the apical and then the basolateral membranes or the opposite way
Paracellular transport
Crosses the pithelium through the membrane junctions and lateral intercellular spaces (requires a pump)
Na+ Absorption
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
K+ Secretion
Basolateral Na-K pump will pump K+ into the cell
K+ secreted through apical membrane
Water transport
The intestinal epithelium can transport water in response to osmotic gradient
Passively flows solute transport- solute coupled transport
