Lecture 5-Renal Blood Flow And GFR Flashcards
Which type of nephron is the most abundant in kidney?
Cortical nephron
What are the differences between cortical and juxtamedullary nephrons?
- cortical: short loop of Henle, lots of renin, rich sympathetic nerve innervation
- juxtamedullary: long loop of Henle, almost no renin, poor sympathetic nerve innervation
What % of blood from the renal artery is filtered at any one time at the glomerulus?
20%
What makes up the renal corpuscle?
Glomerulus and Bowman’s capsule
True or false: proteins are small enough to be filtered by the glomerulus
FALSE - too large
What are the three layers of the filtration barrier?
- capillary endothelium
- basement membrane
- podocytes
What is the capillary endothelium permeable to?
Water, salts and glucose
What is the basement membrane permeable to?
Small proteins
What is the basement membrane made of?
Acellular gelatinous layer of collagen/glycoproteins
What do podocytes form?
Form fenestrations/filtration slits
A molecule under what weight and what radius can pass through the filtration barrier of the glomerulus?
5200 (weight)
1.48 nm
True or false: anions are attracted to the filtration barrier so more are filtered
FALSE - cations are attracted because of the negatively charged glycoproteins in the basement membrane
What happens to the filtration barrier for proteinuria to occur?
Negative charge is lost so proteins (anions) are readily filtered
What makes up the net filtration pressure?
Hydrostatic pressure in capillary + hydrostatic pressure in Bowman’s capsule + oncotic pressure difference
When is renal autoregulation used?
For acute changes, to keep renal blood flow and GFR constant
What are the two responses of renal autoregulation?
Myogenic mechanism
Tubuloglomerular feedback
Describe the myogenic response if renal BP is high
Constriction of afferent arteriole so less blood arrives at the glomerulus or dilate efferent arteriole (to decrease GFR)
Describe the myogenic response if renal BP is too low
Dilate afferent arteriole or constrict efferent arteriole (to increase GFR)
In which arteriole is the myogenic response more common?
Afferent
What stimulates tubuloglomerular feedback?
Concentration of NaCl detected by NKCC2 channel on the apical membrane of macula densa (DCT)
What does the macula densa stimulate to release different chemicals as part of the tubuloglomerular feedback mechanism?
Juxtaglomerular apparatus
Describe the tubuloglomerular feedback mechanism to decrease GFR
Adenosine released:
- activation of A1 receptors -> constriction of afferent arteriole
- activation of A2 receptors -> dilation of efferent arteriole
Describe the tubuloglomerular feedback mechanism to increase GFR
Prostaglandins released -> dilation of afferent arteriole
