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Physio-RBF&GFRI&II

QuestionAnswer
State the relationship between flow, resistance, and pressure in mathematical form Q = (Diff of P)/R
Define Glomerular Filtration Rate (GFR) The volume of filtrate formed per unit time
Describe in both words and equation form the relationship between hydraulic permeability, surface area, and net filtration pressure as they determine rate of filtration -Rate of filtration (GFR) = hydraulic perm. x surface area x NFP -Hydraulic permeability, surface area, and net filtration pressure as they determine rate of filtration are all proportional to form the rate of filtration
List and describe the Starling forces that determine NFP, net filtration pressure -NFP = (PGC–PBC-(Pi)GC) *PGC= glomerular-capillary hydraulic pressure *PBC= Bowman's capsule hydraulic pressure (Pi)GC= Glomerular-capillary oncotic pressure
Describe, using words or a graph, how the Starling forces and, thus, NFP change along the length of the glomerular capillary Slides 18 & 19
Describe how changes in afferent arteriolar resistance affect PGC and Renal Plasma Flow (RPF); do the same for efferent arteriolar resistance -Afferent: GFR decreases because both glomerular pressure & renal plasma flow fall -Efferent: GFR increases because rising capillary pressure dominates; then decreases because faling RPF dominates -Slide 25 & 26
Describe the effect of increases and decreases in afferent and efferent arteriolar resistances on GFR -Afferent: *Decrease R: Increases GFR *Increase R: Decrease GFR
Draw a graph that shows the relationship between renal blood flow and GFR Slide 21
Given numerical values for Starling forces, be able to determine whether filtration or reabsorption occurs in the peritubular capillaries
Describe what happens to the Starling forces in the peritubular capillaries as a result of volume expansion -Expansion (vasodilation of afferent and efferents): PGC (vasodilating the afferent,efferent): Increase, Decrease -Increase HP in PTC -Decrease OP in PTC
Describe what happens to the Starling forces in the peritubular capillaries as a result of volume contraction -Contraction (vasoconstriction of afferent and efferents): PGC (vasoconstriction the afferent,efferent): Decrease, Increase -Decrease HP in PTC -Increase OP in PTC
Given scenarios that indicate the resistance changes in the efferent and afferent arterioles, be able to determine what happens to GFR, RBF, and filtration fraction. Be able to describe the subsequent effects on the peritubular Starling forces
Define tubuloglomerular feedback. Be able to predict the resistance changes (due to tubuloglomerular feedback) in the afferent arteriole subsequent to a decrease in renal perfusion pressure and an increase in renal perfusion pressure Changes in GFR are detected by the renal tubule, which sends feedback signals to the glomerulus, initiating a cascade of events that ultimately brings GFR to an appropriate level
Describe the sympathetic and hormonal effects on GFR and RPF (Part 1) -RAAS system: Ang II constricts afferent and efferent arterioles (efferent more than afferent) -SNS: constricts both afferent and efferent arterioles -Net effect: Decrease in RPF w/ only a little or no change in GFR
Describe the sympathetic and hormonal effects on GFR and RPF (ADH) ADH (AVP): does vasoconstrict, but normally RBF and GFR remain constant
Describe the sympathetic and hormonal effects on GFR and RPF (ANP) -vasodilates afferent and vasoconstricts efferent arterioles (probably the former more than the latter), thus causes increases in both RBF and GFR -also inhibits the secretion of renin
Describe the sympathetic and hormonal effects on GFR and RPF (Part 2) -Epinephrine: acts like NE -Dopamine (low dose): causes vasodilation
Given plasma values for a substance and for those parameters used to calculate GFR, be able to calculate the filtered load of a substance. (see page 33, Vander). This will be a homework assignment
Effect of solute characteristics on filtration -Molecular Size -Electrical charge -Shape -Solute is protein-bound??????
Rate of Filtration GFR = Kf x NFP
Direct relationship between RBF and GFR -Increase RBF, Increase GFR -Decrease RBF, Decrease GFR
Filtration Fraction -volume of filtrate from a given volume of plasma entering the glomeruli -FF = GFR/RPF -FF is greater at low plasma flow than at high flow
Example of when afferent or efferent resistance dominates Decrease in afferent R dominates: after nephrectomy, get large increase in GFR in the remnant kidney due to a decrease in the R of the afferent arteriole
With SNS stimulation (and angiotensin II), BOTH afferent and efferent resistances increase, and RBF decreases (and ANG has a preferential efferent effect)
Tubuloglomerular Feedback (Key Concept 1) -Increases and decreases in GFR are reflected as increases or decreases in NaCl sensed by the Macula Dense, respectively
Tubuloglomerular Feedback (Key Concept 2) Paracrines from Macula Densa scoot over to the afferent arteriole to constrict or dilate that vessel
Describe the sympathetic and hormonal effects on GFR and RPF (Part 3) -Prostaglandins: *They can help maintain RBF and GFR when there is high sympathetic outflow and lots of RAAS
Created by: jgrayson
 

 



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