Renal Blood Flow and Glomerular Filtration - Rao Flashcards
What two vascular structures have the highest resistance in the nephron? What is a distant third?
Efferent Arteriole > Afferent Arteriole > Peritubular Capillary
What is the Gibbs Donnan effect?
4-5% more anions than cations present in filtrate because cations can bind negatively charged proteins in plasma
What is the equation for filtration fraction?
FF = GFR / RPF
Name one factor that can reduce GFR and one that can reduce RPF?
GFR - urethral obstruction
RPF - renal artery stenosis
What are the three filtration barriers in the glomerulus?
Capillary Endothelium
Basement Membrane
Epithelium (Podocyte monolayer)
What is an equation for GFR?
GFR = Kf x Net filtration pressure
What is Kf?
Filtration coefficient = hydraulic conductivity x surface area of glomerular capillary
What is the equation for net filtration pressure?
(P g + Pi bs) - (Pi g + P bs) g -glomerulus bs - bowman's space P - hydrostatic Pi - oncotic
How does increased afferent or decreased efferent arteriole pressure effect GFR?
Decreases GFR
How does decreased afferent or increased efferent arteriole pressure effect GFR?
Increases GFR
How does increased afferent arteriole pressure affect GFR and RPF, respectively?
GFR - decrease
RPF - decrease
How does decreased afferent arteriole pressure affect GFR and RPF, respectively?
GFR - increase
RPF - increase
How does increased efferent arteriole pressure affect GFR and RPF, respectively?
GFR - increase
RPF - decrease
How does decreased efferent arteriole pressure affect GFR and RPF, respectively?
GFR - decrease
RPF - increase
How does increased hydrostatic pressure in bowman’s space affect GFR?
Decreases GFR (through decreased net filtration rate)
How does low capillary flow affect GFR?
Low capillary flow - Increased filtration fraction - Increased glomerular oncotic pressure - Decrease net filtration pressure - Decrease GFR
How do GFR and RPF remain constant through a range of mean arterial pressures?
Change renal vascular resistance (particularly afferent arteriole)
What is the mycogenic mechanism?
Major theory of GFR auto-regulation
Direct simulation of arteriolar smooth muscle
What is the tubuloglomerular feedback mechanism?
Major theory of GFR auto-regulation
Juxtaglomerular apparatus (macula densa cells and juxtaglomerular cells)
Stimulated by GFR and tubular chloride
High flow / chloride causes decreased GFR
How does high chloride in macula densa decrease GFR?
High chloride stimulates NA-K-2Cl cotransporter in JG cells
JG cells release ATP and AA metabolites
Smooth muscle contraction
Increase arteriolar resistance
What activates the Renin Angiotensin System?
Decreased arterial pressure
Decreased ECF volume
List the cascade of events from stimulation to effect of the RAS.
Decreased arterial pressure / ECF volume
Decreased glomerular hydrostatic pressure / GFR
Decreased chloride at macula densa
Renin secretion from juxtaglomerular cells
Increased angiotensin I
Increased angiotensin II (constricts arterioles and decreases GFR)
Aldosterone
Na and water retention
How does sympathetic activation affect GFR?
Constrict afferent arterioles and decrease GFR
How does adrenaline affect GFR?
Constrict arterioles (preferentially afferent) and decrease GFR
