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Phys3 RBF & GFR

QuestionAnswer
Physical solute characteristics of filtrate 1.Low molecular wgt. 2.small radius. 3.MARCOmolecules w/ Positive charge (due to neg BM & podocytes). 4.Deformable molecules (non-rigid, non-globular). 5.Non protein bound.
Net Filtration Pressure (NFP) NFP=(Pgc-πgc)-(Pbc-πbc).
Names for π 1.oncotic. 2.Collod osmotic. 3.Osmotic
Factors that increase the magnitude of the direct determinant: Kf 1.Inc glomerular surface area (via relaxation of mesangial cells). **Inc GFR
Factors that increase the magnitude of the direct determinant: Pgc 1.Inc renal arterial pressure. 2.Dec Afferent resistance (Afferent VD). 3.Inc Efferent resistance (Efferent VC). **Inc GFR
Factors that increase the magnitude of the direct determinant: Pbc 1.Inc intratubular pressure due to obstruction. **Dec GFR
Factors that increase the magnitude of the direct determinant: πgc 1.Inc systemic-plasma oncotic pressure. 2.Dec renal plasma flow. **Dec GFR
What happens to GFR if Pbc or πbc decrease? INCREASES.
What happens to GFR if Kf or Pgc decrease? DECREASES.
How would vasoconstriction of afferent arteriole affect GFR? Dec Pgc: Dec RBF: Dec GFR.
How would vasodilation of efferent arteriole affect GFR? Dec Pgc: Inc RBF: Dec GFR
How would vasoconstriction of both arterioles affect GFR? Big Dec in RBF, GFR stays the same.
As you move down the glomerular capillary from afferent to efferent what happens to the NFP? why? It decreases b/c the πgc is slowly increasing while Pgc stays relatively the same. **πgc slowly increases b/c fluid is being filtered out of the capillary.
Does Pbc change with capillary length? NO
What happens to NFP with LOW glomerular plasma flow? It decreases rapidly along the length of the capillary due to quickly Inc πgc. Thus Dec GFR **creates wasted capillary.
what happens to NFP with HIGH glomerular plasma flow? πgc doesn't rise as fast so NFP decreases at a very slow rate. this Inc GFR. **Inc delivery of fluid outpacesthe filtration, πgc doesn't rise as fast.
At any given length along the capillary, there is a ________ NFP with higher flow rate? GREATER. **filtration also occurs along a greater length of the capillary.
What is the relation b/w GFR and RBF? DIRECTLY RELATED: Inc RBF -> Inc GFR. Dec RBF -> Dec GFR.
Do GFR and RBF increase linearly? NO, the effect on GFR saturates at high plasma flows. **This occurs at RBF 600ml/min which produces a GFR of 125ml/min.
Filtration (FF) represents the volume of filtrate that forms from a given volume of plasma entering the glomerulus. **Greater at lower flows, less at higher flows.
Equation for FF FF = GFR/RBF
Effects of Pgc, RBF, GFR, and FF: Afferent vasoconstriction (Inc resistance) 1.Pgc:Dec. 2.RBF:Dec. 3.GFR:Dec. 4.FF:
Effects of Pgc, RBF, GFR, and FF: Afferent vasodilation (dec resistance) 1.Pgc:Inc. 2.RBF:Inc. 3.GFR:Inc. 4.FF:Dec.
Effects of Pgc, RBF, GFR, and FF: Efferent vasoconstriction (inc resistance) 1.Pgc:Inc. 2.RBF:Dec. 3.GFR:Inc. 4.FF:Inc.
Effects of Pgc, RBF, GFR, and FF: Efferent vasodilation (dec resistance) 1.Pgc:Dec. 2.RBF:Inc. 3.GFR:Dec. 4.FF:Dec.
Can arteriolar resistance changes (VD & VC) lead to changes in flow tha influence GFR independent of effects on Pgc? YES, they can cause a change in RBF which will affect FF. **FF=GFR/RBF
How does the effect of increasing EFFERENT arteriolar resistance change the factors influencing GFR? 1.Mild/moderate resistance: Pgc dominates which will cause an INCREASE in GFR. 2.Moderate/high resistance: RBF dominates which will cause a DECREASE in GFR (b/c RBF is decreasing)
effects of a Nephrectomy on GFR Decreased afferent arteriolar Resistance causes a large INCREASE in GFR.
effects of ACE inhibitors/ANG II blockers on GFR Decreased efferent arteriolar resistance will DECREASE GFR at the same renal artery pressure below 105mmHg. **could lead to renal failure. ANG II is an important GFR autoregulator.
Arteriolar preference of ANG II EFFERENT arteriole. SNS stimulation with ANG II will cause a VC of both afferent and efferent arterioles, however the effect is greater on the EFFERENT so the Pgc will INCREASE. **keeps a more constant GFR despite RBF decrease.
Vasa Recta Formed from the effernet capillaries from the juxtamedullary nephrons. **they follow the tubules deep down into the medulla.
What are the 2 main forces governing the dynamics in the Peritubular capillaries (PTCs) 1.Starling forces: make the PTCs favor reabsorption b/c π(PTC) is Inc due to fluid filtration and P(PTC) is DEC due to efferent VC. 2.Glomerular Dynamics: determines starling forces.
Why is reabsorption favored in the PTCs? 1.High osmotic pressure π(PTC). 2.Low hydrostatic pressure P(PTC).
Reflex response to volume expansion (effects on kidneys) 1.Dec SNS & RAAS. 2.VD of afferent & efferent. 3.Large Inc in RBF. 4.small Inc in GFR (slight dec due to ANG II & efferent VD). 5.Dec FF. 6.Dec fluid through BC. 7.Inc P(PTC) (due to VD efferent). 8.Dec π(PTC) (due to dec FF & Inc RBF). 9.EXCRETI
Reflex response to volume contraction (effects on kidneys) 1.Inc SNS & RAAS. 2.VC afferent & efferent (more so efferent b/c ANG II). 3.Large Dec RBF. 4.small Dec GFR. 5.Inc FF. 6.Inc fluid through BC. 7.Dec P(PTC) (due to VC of efferent). 8.Inc π(PTC) (due to Inc FF & Dec RBF). 9.REABSORPTION.
2 Autoregulatory prcoesses keeping RBF & GFR from varying too widely (this protects the kidney) 1.Myogenic response (as BP Inc, so does Resistance & vica versa, this keeps flow the same). 2.Tubuloglomerular feedback (Dec BP Dec GFR & Dec NaCl which causes macula densa to paracrine VD afferent arteriole. Vica versa is true).
Renal Autoregulation: Tubuloglomerular feedback: High BP (or pressure in afferent arteriole) Causes: 1.Inc GFR. 2.Inc NaCl. Macula Densa release paracrine hormones causing: 1.Afferent VC. 2.Dec GFR (via Dec RBF). 3.Dec NaCl
Sympathetic effects on RBF and GFR VC both afferent and efferent arterioles. 1.DEC RBF. 2.slight Dec or relatively constant GFR. **Inc FF.
RAAS effects on RBF and GFR ANG II constricts afferent & efferent arterioles (efferent more so than afferent). 1.Dec RBF. 2.GFR relatively constant (smaller decrease due to Inc Pgc). **Inc FF.
ADH effects on RBF and GFR Total RBF & GFR remain fairly constant despite some VC.
ANP effects on RBF and GFR VD afferents and VC efferents. 1.Inc RBF (VD afferents more than VC efferents). 2.Inc GFR. **Dec FF and inhibits renin secretion.
When are protstaglandins helpful in regulating GFR and RBF? during high SNS and RAAS outflow. It protects against excessive vasoconstriction.
Created by: WeeG
 

 



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