Glomerular Filtration Flashcards
what types of molecules are excluded from the glomerular filtration barrier?
large, negatively charged things
what does “perm selectivity” mean?
size and charge selective
what are characteristics of the glomerular capillaries?
- high hydrostatic pressure
- constant hydrostatic pressure
- large surface area for filtration
what is the charge of the basement membrane?
negative- repels large negative things, attracts positive things
what are the proteins in the filtration slit?
nephrin
podocin
what does nephrin do?
filtration slit protein
extracellular, linked to podocin inside foot process
what does podocin do?
filtration slit protein
inside foot processes, connects to nephrin and signals EC events
what does damage to the filtration slit do?
changes permeability
what is the clearance ratio formula?
Cx/Cinulin
why is inulin special?
inulin is freely filtered
anything larger than inulin is not filtered
what properties of a molecule will change its clearance ratio and how?
increased size –> decreases clearance ratio
increased positive charge–> increases clearance ratio
increased negative charge–>decreases clearance ratio a lot
what is serum nephritis?
increased anion filtration due to loss of negative charge at filtration barrier
what is the starling formula for glomerular filtration?
GFR = Kf [(Pc-Pbs) - COPx]
Kf- glomerular filtration constant (surface area and permeability)
Pc-Pbs- transmural hydrostatic pressure
COP- colloidal protein osmotic pressure
what is the ultrafiltration pressure equation?
Puf = (Pc - Pbs) - COPx
always positive or 0
how does COP change along the glomerular capillary?
increases (afferent < efferent)
water is removed, which concentrates the remaining solutes
how does the ultrafiltration pressure change along the length of the capillary?
decreases because COP increases
when is the glomerular filtration in equilibrium?
COP = hydrostatic pressure
what is normal GFR?
100-120ml/min (180L/day)
what happens at filtration equilibrium?
no reabsorption
what does glomerular filtration depend on?
blood flow and pressure gradient
how does filtration fraction vary with renal plasma flow?
normal 15-20%
low- 20%
high <15%
what is the effect of decreasing arteriolar resistance?
increases renal plasma flow, glomerular pressure, and GFR
what is the effect of increasing arteriolar resistance?
decreases RPF, glomerular pressure, and GFR
what controls renal blood flow?
sum of afferent and efferent resistances
what controls glomerular capillary pressure?
relative resistances of the afferent and efferent arterioles
what is the most important regulator of RPF and GFR?
afferent arteriole resistance
what is the effect of decreasing efferent arteriole resistance?
increases RPF
decreases glomerular capillary pressure and GFR
what is the effect of increasing efferent arteriole resistance?
decreases RPF
increases glomerular capillary pressure
decreases GFR with large change, increase with small
where does angiotension II preferentially act? what does it do?
constricts the efferent arterioles
what do changes in GFR affect?
Na excretion
- water excretion is affected by tubular water reabsorption
what are extrinsic controllers that result in decreased GFR?
sympathetic nerves- adrenergic and catacholamines antiotension II vasopressin (ADH) endothelin, thromboxane dehydration, hemorrhage
what are extrinsic controllers that result in increased GFR?
ANP, dopaminergic nerves, NO
prostaglandins
high dietary proteins, pregnancy
