Colin's Lectures Flashcards
Renal filtration is size and charge specific.
What size molecules are filtered / not filtered?
<1.8nm -> easily filtered
1.8 - 3.6 -> cations filtered, anions repelled
>3.6nm -> not filtered
Define filtration coefficient
Determines the membrane’s ability to filter water and solutes across it.
Ranges from 0 to 1
0 = impermeable
1 = freely permeable
What is osmotic pressure
The minimum pressure that stops the osmosis across a semi-permeable membrane
1 m osml = how many units of hydrostatic pressure?
19mmhg
What is the Gibbs Donnan effect
Extra osmotic pressure due to the extra Na and K ions helpsd in the plasma by the plasma proteins
Capillary osmotic pressure hence = 19 + 7 = 26mmHg
What is the difference between filtration and reflection coefficient.
Filtration coefficient = ability of a membrane to filter water and solute across it
Reflection coefficient = ability of a membrane to reflect protein molecules
Describe how myogenic auto regulation occurs?
Increased flow = increased stretch
Activates stretch sensitive Gq GPCR
-> Increase IP3 -> increase intracellular calcium -> potentiates MLCK -> SM contraction
What is the MOA of mannitol
20% solution given at 0.5mg/kg.
Raises baseline serum osmolality by 20mOsm/L
Fluid shift ICF -> ECF
High urine osmotic concentration -> impairs H2O reabsorption
Initial increase in intravascular volume, then decrease in IVV.
What are the complications of acetazolamide
NAGMA due to bicarbonaturia
Normal to low K+
- Increased K loss but compensated by acidosis (Na/K antiport activity)
What is the MOA of amiloride and triamterene?
blocks the apical sodium channel to decrease Na reabsorption
What is the acid-base effect of spironolactone
Aldosterone inhibitor
- Reduce action of Na/K action
- Reduce ENac expression on apical membrane
Reduced electrogenic exchange of Na for K/H. This can cause hyperkalaemia and acidosis
Where does the action of NH4, ammonium buffer system take place?
PCT - glutamine metabolism to make 2 new HCO3- and secrete 1 NH4+
TA LOH - ammonium ion competes with K+. Contributes to high medullary osmolality. Also can be secreted into collecting duct
Tubular cells of CCT and collecting duct - 2/3 of NH3+ excreted via the Rh proteins and combine with H and Cl for excretion
Why does acadaemia increase renal ammonium buffer system?
Acidaemia = increased glutamine production
Urea synthesis is inhibited under acidosis and glutamine synthesis becomes more dominant
How does aldosterone affect acid base system
Chronically high or low aldosterone levels lead to AB abnormalities
Aldosterone stimulates
- H+ ATPase pump -> combines with ammonium buffer pair + chloride lost
- Combine with phosphate buffer pairs
- Stimulates H/K+ exchange pump to to increase in SID
