Glomerular Filtration and Renal Clearance Flashcards
- What components of blood are able to pass through the filter at the glomerulus?
- What components are turned back and remain in the blood?
- Describe the path that fluid takes to get from the blood to the filtrate.
- For a given substance, if the ratio of its concentration in Bowman’s space / concentration in plasma is 1, then it is […]. If it is less than 1 then it is […].
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What controls filtration fraction?
Renal excretion = ?
Bottom of slide
Within the category of autoregulation that happens at the kidney, there are 3 main mechanisms that te kidney employs to accomplish this effect. What are they?
In systemic arteries, when blood pressure increases, it stretches the vessel walls and thus the smooth muscle. This causes a reactionary contraction of the smooth muscle leading to vasoconstriction and increased resistance. Increased pressure is met with increased resistance to keep the flow rate essentially constant. This is the same as the myogenic response we saw in the CV system.
Filtrate is [hypotonic/isotonic/hypertonic] to plasma.
Isotonic
The table below shows the neurotransmitters that exert extrinsic regulation of GFR.
Complete the table below and indicate their effects on afferent / efferent arterioles of the glomerulus.
The table below shows the compounds that exert extrinsic regulation of GFR to cause vasodilation.
Complete the table below and indicate their effects on afferent / efferent arterioles of the glomerulus.
What are the ways in which the body regulates GFR?
What is the normal contents of plasma?
How does this compare to the normal contents of filtrate?
What is renal clearance?
The rate of elimination of a substance from the plasma
Renal excretion = Amount filtered - Amount Reabsorbed + Amount secreted
[…] and […] are the major factors that determine what is filtered and what remains behind in the blood
Size
Charge
For each of the diagrams in this image representing the afferent arteriole, glomerulus, and efferent arteriole, what would happen to the following parameters:
- Resistance
- RBF
- Pressure of glomerular capillaries
- GFR
- FF
- See image for first 4 parameters
- FF is unchanged in A and D
- FF is higher in B
- FF is lower in C
How would you simplify this equation to make it appropriate for the level of detail we’re discussing this year?
Sigma is 1 for glomerular capillaries
Pi_BS is 0 b/c Pi is oncotic pressure and there’s no proteins in Bowman’s space to exert an oncotic pressure
- Work through the mathematical example on this slide to determine the total pressure driving filtration at the afferent and efferent ends of the glomerulus.
- What would happen to GFR if the parameters in the table were changed as indicated? What are some physiologic/pathologic conditions that could cause these to happen?
- In healthy individuals, how is GFR regulated?
Describe the mechanism of autoregulation called glomerulotubular balance.
This measure of autoregulation is taken secondary to tubuloglomerular feedback. With increasing GFR without changes in volume of blood, the body can increase the amount of solute reabsorption in the proximal convoluted tubule. Increased reabsorption in PCT in face of increased GFR restores normal fraction of filtered load that is reabsorbed in PCT (67%) by the time filtrate reaches DCT, so this protects the distal nephron from overload in the face of short term increases in GFR.
A
A
Describe the mechanism of autoregulation called tubuloglomerlar feedback.
Most reabsorption, specifically of Na+, occurs in the PCT. If GFR is too high, this means that filtrate is being produced too quickly and it will flow through the nephron at a rate that outpaces reabsorption. This means that there will be relatively high Na+ in the filtrate after it leaves the PCT because it cannot be reabsorbed as fast as it is being filtered. When the filtrate reaches the DCT the macula densa will detect the high Na+ and signal to the adjacent juxtaglomerular apparatus to cause constriction of the afferent arteriole, which will lead to increased resistance, decreased RBF and decreased GFR.
