WEEK 9: 9.3 Glomerular Filtration Rate Flashcards
(28 cards)
How does the permeability of the glomerular capillary compare to other capillaries?
the glomerular capillary is much more permeable to water due to the presence of fenestrae and capillary junctions
Podocytes contracting causes what to occur?
reduced filtration, as this narrows the filtration slits that regulate what passes into Bowman’s capsule
Why is the glomerular basement membrane charged?
It is negatively charged to repel negatively charged proteins, hence maintain selective filtration
What is the effect of sympathetic stimulation on podocyte contraction?
It causes podocyte contraction, decreasing GFR and kidney filtration (Kf)
What is the normal range for GFR?
90-140 ml/min
Is GFR the same for males and females?
females have a lower GFR than males because males are larger
Does GFR change with age?
Yes, it reduces as one ages.
Why is it important to keep GFR within a specific range?
To maintain fluid and electrolyte balance
What is the autoregulatory range?
mean arterial pressure of 80 - 180 mmHg over which glomerular filtration rate and renal blood flow remain relatively constant despite changes in systemic blood pressure
Does GFR change with changes in blood pressure?
typically not, within the autoregulatory range, however hypertension can cause higher GFR
What are the 4 starling forces at the glomerulus that determine net filtration pressure across the glomerular capillary wall?
glomerular hydrostatic pressure
bowman’s capsule pressure
glomerular oncotic pressure
net filtration pressure = glomerular hydrostatic pressure - (bowmans capsule pressure + glomerular oncotic pressure)
What if glomerular pressure can’t be regulated
This results in glomerular damage, high pressures cause capillary wall injury while low pressures cause inadequate filtration and toxin buildup
unrecoverable
What does the filtration coefficient Kf represent?
the permeability and surface area of the glomerular membrane
What is the equation for GFR
Kf x net filtration pressure
How does vasoconstriction decrease GFR?
it decreases glomerular capillary blood pressure and decreases net filtration pressure
How does vasodilation increase GFR?
it increases glomerular capillary blood pressure and increases net filtration pressure
How does adjusting afferent arteriole blood flow affect GFR?
increasing it increases GFR
decreasing it decreases GFR
this can be achieved by adjusting the radius of the afferent arteriole
What is the role of extrinsic sympathetic stimulation in GFR regulation?
It is aimed at long-term regulation of arterial BP
Which hormones are involved in hormonal regulation of GFR?
angiotensin II and atrial natriuretic peptide (ANP)
What is the myogenic mechanism in GFR control
Increased pressure in afferent arteriole causes vessel stretch, leading to constriction, increased resistance and reduced flow
What is tubuloglomerular feedback
a mechanism involving the macula densa sensing salt concentration, influencing afferent arteriole tone via granular cells
What happens when GFR increases and macula densa detects increased salt and flow??
ATP and adenosine are released, causing afferent arteriole constriction and lowering GFR and lowering renin secretion to increase sodium excretion
What happens when the macula densa detects low salt and flow?
It releases nitric oxide or PGI2, causing vasodilation of the afferent arteriole & to increased renin secretion to conserve sodium
What do granular cells release, and what is their function?
they release renin, and are involved in regulating blood pressure and GFR
