Exam 1: RBF And GFR Flashcards
How much CO do the kidneys receive?
1/4 of the cardiac output
How many liters of filtrate are formed per day?
180 liters
What is the equation for filtration fraction (FF)?
GFR/RPF
What is normal RBF?
1.1 L/min
What is the equation to calculate Renal plasma flow (RPF)?
(1-Hct)(RBF)
What are the vasoconstrictors to regulate RBF?
Sympathetic nerves via Alpha 2 receptors and Angiotensin II, ADH, ATP, and endothelin
What are the vasodilators that work to increased RBF and GFR?
Atrial natriuretic peptide (ANP), glucocorticoids, NO, and prostaglandins
What is autoregulation?
Constant blood flow and GFR though a range of arterial pressures
What are the two mechanisms that contribute to autoregulation?
The myogenic mechanism and the tubuloglomerular feedback mechanism
What is Tubuloglomerular feedback?
Increasing GFR increases NaCl delivery to the LOH, this is sensed by the macula densa which causes resistant to the afferent arteriole to increase thereby decreasing RBF and GFR
What is Kf?
The filtration rate produced by each mmHm of net filtration pressure
Tubuloglomerular feedback maintains the constancy of ** delivered to the **.
Salt
Distule tubule
What are the main barriers to proteins in regards to glomerular filtration?
Basal lamina and filtration slits
What is PGC?
Blood pressure in glomerular capillary, which is the driving force for GFR
What is PBC?
Back pressure in Bowman’s capsule, which reduces GFR
How are PGC and GFR related?
Directly, as PGC increases so does GFR
When afferent and efferent arteriolar resistances increase, what is the effect on PGC and RBF?
No effect on PCG, but dramatic decrease in RBF
What happens to PGC and RBF when afferent arteriolar resistances increase?
Both PGC and RBF decrease
What happens to PGC and RBF when the efferent arteriolar resistances increases?
PGC increases and RBF decreases
What do PGE2 and PGI2 do?
They vasodilator the afferent arterioles by reducing vasoconstriction produced by the SNS stimulation to maintain blood flow
What do NSAIDs do to prostaglandins?
They inhibit the synthesis of prostaglandins by inhibiting the activity of COX1 and 2.
What is tubular secretion?
When solutes go from the peritubular capillary to the tubular lumen
What equation describes GFR?
Starling equation:
GFR= Kf (Pgc -Pbc) - (πgc -πbc)
What is Pgc?
Blood pressure in the glomerular capillary (the driving force for GFR)
What is Pbc?
The back pressure in Bowman’s capsule (reduces GFR)
What is πgc?
Oncotic pressure in glomerular capillary blood (due to proteins being unable to cross the barrier and retards GFR)
When does πgc increase?
AS plasma is diverted into Bowman’s capsule
What is πbc?
The oncotic pressure in Bowman’s capsule, but its usually zero because there are not normally proteins in Bowman’s capsule
Why is Angiotensins effect on GFR variable?
AT II constricts both afferent and efferent, but efferent is more sensitive. Low dose AT II will mostly affect efferent
What is the equation for NFP?
NFP= (Pgc -Pibc) - (Pbc- Pigc)
What happens to RBF and GFR with high concentrations of AT II?
Decreased GFR and RBF (both afferent and efferent arterioles are constricted)
What happens to RBF and GFR in low doses of AT II?
GFR is unaffected and RBF is decreased (only efferent arteriole is constricted)
