What are the three barriers which make up the glomerular membrane?
Endothelium of glomerular capillaries
Podocytes of Bowman's capsule and their slit processes
Glomerular capillaries are more ___ than other capillaries.
What is the glomerular basement membrane made up of?
Type IV collagen
(Goodpasture's syndrome is a Type II hypersensitivity reaction where antibodies attack the Type IV collagen of the basement membrane)
What charge does the glomerular basement membrane have?
What's good about the negativity of the glomerular basement membrane?
Large negatively charged proteins can't pass through it
Is filtration an active or passive process?
What is hydrostatic pressure?
What is oncotic pressure?
Pressure exerted by negatively charged plasma proteins
The glomerular capillaries have a high, constant ___.
What is the fluid pressure within Bowman's capsule called?
Does it push fluid in or out of the glomerular capillaries?
Bowman's capsule HYDROSTATIC pressure
Pushes fluid INTO capillary
What type of pressure keeps plasma proteins within the capillary?
What causes this?
Capillary oncotic pressure
Negatively charged basement membrane
What is the value of the oncotic pressure of Bowman's capsule?
No plasma protein in the capsule
a) aid filtration
b) block filtration?
a) Capillary blood pressure
b) Bowman's capsule hydrostatic pressure, capillary oncotic pressure
What is the name for the total force which aids glomerular filtration?
What value does it have?
Net filtration pressure
What is GFR?
Glomerular filtration rate
Rate of filtration of protein-free plasma into Bowman's capulse per unit time
What is the equation for GFR?
GFR = Kf x net filtration pressure
Kf = filtration coefficient, or how permeable the glomerular membrane is
Net filtration pressure was 10 mmHg according to last slide
What is the main determinant of GFR?
Capillary hydrostatic pressure
which is the strongest force pushing plasma out of the capillaries
What is the normal GFR?
What extrinsically regulates GFR?
Sympathetic nervous system
via Baroreceptor reflex
Increasing glomerular capillary blood pressure also increases ___.
What increases and decreases capillary blood flow and therefore blood pressure, GFR?
Vasodilation of afferent arteriole increases GFR
Vasoconstriction of afferent arteriole decreases GFR
How do you calculate MABP?
((2 x diastolic) + (systolic)) / 3
How does renal blood flow and therefore GFR react to short term changes in blood pressure?
Not very much
autoregulation to prevent water and electrolyte imbalance
When is autoregulation of renal blood flow and GFR useful?
Exercise - BP increases but you don't want to lose too much water and electrolytes
Low BP - you still want to filter adequately
What is myogenic regulation of GFR?
Increased blood flow / BP causes walls of arteriole to stretch
Automatic constriction of smooth muscle to reduce blood flow > reduce GFR
Keeps GFR the same during short term hypertension/hypervolaemia
Which part of the distal tubule regulates GFR?
If solute concentration in the distal tubules increases, which cells cause smooth muscle constriction in the afferent arteriole to reduce blood flow and therefore GFR?
Macula densa cells detect inc salt
Granular/juxtaglomerular cells cause smooth muscle constriction
This is the short term regulation, juxtaglomerular apparatus also involved in RAAS which is the long term regulation
How do kidney stones affect GFR?
Blockage in collecting system, buildup of filtrate
so Bowman's hydrostatic pressure increases, stronger force AGAINST plasma movement into capsule from capillary, GFR decreases
How does diarrhoea affect GFR?
Same amount of plasma protein
Capillary oncotic pressure increases (against movement OUT of capillary into bowman's)
What is Kf a measure of?
i.e surface area available for filtration