Lec 29 Flashcards
GFR is — over wide range of –
constant over raange of BP
GFR is regulated by —-
regulationg renal blood flow
autoregulation
constant GFR when MAP is between 80 and 180
regulate blood flow into glomerulus by
Vasoconstriction and vasodilation of afferent arteriole
Vasoconstriction of efferent arteriole
minimal leave
blood pulls in glomerulus
increase Ph
GFR increase
Vasoconstriction of afferent arteriole
less blood entering glomerulus
decrease Ph
decrease GFR
Vasodilation of afferent arteriole
more blood entering glomerulus
increase ph
icrease GFR
mechansim of autoregulation
1-myogenic response to changes in BP
2-vasoconstriction afferent arteriole
3- tubuloglomerular feedback
myogenic response to changes in BP:
1- intrinsic ability of vascular smooth muscle
2- stretch due to increased pressure causes vasoconstriction
stretch due to increased pressure causes vasoconstriction, how
1- stretch-activated cation channels on vascular smooth muscle
2- depolarization lead to smooth muscle contraction
tubuloglomerular feedback
paracrine signalling
- occurs at the juxtaglomerular apparatus (JGA)
- Macula densa: specialized cell in ascending tubule sensing flow
JGA
region where ascending limb loop of henle passes between afferent and efferent arterioles
macula densa function
sense increase flow due to high GFR
release paracrine
paracrine act on afferent arteriole
Vasoconstriction
granular cells
secrete renin, enzyme involve in salt and water balance
tubuloglomerular feedback
gfr increase
flow through tubule increase
flow past macula densa increase
paracrine from macula densa on afferent arteriole
Vasoconstriction
resistance increase
hydrostatic pressure decrease
gfr decrease
most reabsorption happen in
proximal tubule
reabsorption movement
from tubule lumen into blood
reabsorption transports
transepithelial transport
paracellular pathway
transepithelial transport
transporter apically and basolaterally
paracellular pathway
tight junction of adjacent cells
reabsorption is primarily driven by
Na movement
Na movement through apical membrane
sodium channels called ENaC
no ATP used
conc. gradient
Na movement through basolateral membrane
Na/k pump
ATP needed
when Na is actively reabsoprbed:
1- anions reabsorption by electrochemical gradient
2- water move by osmosis following solute reabsoprtion
3- glucose, amino acid, metabolite, phosphate co-transport
permeable solutes are reabsorbed by
1- paracellular pathway
2- membrane transporters
what happen to k pumping inside proximal tubule by Na/K pump
move out of proximal tubule by K leaky channesls
Glucose reabsorption
soduim-linked secondary active transport
No ATP required
energy comes from potential gradient of Na
glucose diffuse out of basolateral side using
GLUT protein
in glomerulus net driving force cause
filteration
in peritubular capillaries net driving force cause
reabsorption
(80% of fluid remaining but all proteins still here)
Secretion
1-important in homeostatic regulation (K,H)
2-removing organic compound from the body (urea,creatinine,drugs)
3-increase secretion enhances nephron excretion
Excretion
at the end of collecting duct, filtrate can no longer modified
output=urine
shouldn’t contain any glucose, aa, other metabolites
Capillary feeding nephrons
Peritubular capillaries
