! physiology Flashcards
part of the kidney thats esp important in kidneys ability to produce urine of varying concentration
loop of henle
which factor would reduce the net filtration pressure the most?
a large increase in blood colloid osmotic pressure
which forces oppose netfiltration?
- Bowmans capsule hydrostatic – opposes filtration
- Capillary oncotic – plasma proteins trapped in lumen tries to attract fluid from bowmans capsule
osmotic vs oncotic
osmotic pressure = the pressure needed to stop the net movement of water across a permeable membrane which separates the solvent and solution
oncotic pressure = the contribution made to total osmolality by colloids.
affect of afferent arteriolar vasoconstriction on blood flow, netfiltration + GFR
Afferent arteriolar vasoconstriction decreases blood flow into the glomerulus
which causes the glomerular-capillary blood pressure to decrease
leading to a decrease in the net filtration pressure
and a resultant decrease in the GFR
When arterial blood pressure is elevated above normal, which of the following compensatory changes in renal function occur as a result of the baroreceptor reflex?
afferent arteriolar vasodilation
why cant serum albumin be filtered at glomerulus?
its negative + basement membrane also neg
hydrostatic vs oncotic
hydrostatic = balloon = pushes fluid out
oncotic = sponge = draws fluid in
what is the renal threshold?
= plasma concentration of a particular substance at which its Tm is reached and the substance first appears in the urine
(Renal threshold = the concentration of a substance dissolved in the blood above which the kidneys begin to secreted into urine)
RT of gluc = 10-12 mmol/l
aldosterone
stimulates Na reabsorption in distal + collecting tubules
+ stimulates K secretion in distal tubule
potassium (throughout the nephron)
- is filtered, reabsorbed + secreted
- is actively reabsorbed in proximal tubule (NaKATPase)
- is actively secreted in distal + collecting tubules (Na-K-2Cl)
- secretion is controlled by aldosterone
what establishes the medullary vertical osmotic gradient by means of countercurrent multiplication?
loops of Henle of juxtamedullary nephrons
tonicity of tubular fluid from Bowmans capsule to end of loop of Henle
bowmans capsule = isotonic
proximal tubule = isotonic
tip of loop = hypertonic
leaving loop = hypOtonic
which segment of the nephron is not permeable to H2O even in the presence of vasopressin?
ascending limb of loop
how does urine move from the kidneys to the urinary bladder through the ureters?
by peristaltic contraction of the smooth muscle of the ureters
filtration fractions
= fraction of plasma flowing through the glomeruli that is filtered into the tubules
= GFR/renal plasma flow = 125/650 = 20% normally
(remaining 80% moves onto peritubular capillaries)
capillaries in cortical vs juxtamedullary nephrons
cortical = peritubular capillaries
juxtamedullary nephron = vasa recta
where is sodium reabsorbed from in nephron?
everywhere except descending part o loop of henle
what drives resoption of Na?
Na-K ATPase
methods of sodium reabsorption in proximal tubule
- Na dependent glucose transporter - both Na + gluc in
- Na dependent amino acid transports - both in
- Na + H(countertransporter) - Na in, H out
effect of Na reabsorption on Cl- ions
Reabsorption of Na ions via the transcellular route sets up an electrochemical gradient that allows passive paracellular reabsorption of negatively charged chloride ions(Cl-)
- Meaning NaCl reabsorbed to blood which sets up
osmotic gradient - Water follows NaCl passively + via paracellular
transport maximum
max rate at which substance can be reabsorbed
water permability in descending vs ascending loop
descending = permeable, no salt reabsorption
ascending = impermeable, salt resorption
- -> passive in thin, active in thick
- -> no water follows due to tight tight junctions
recycling of K after transport by Na-K-2Cl allows for what
NaCl is absorbed into interstital fluid
what sets up and maintains the cortico-medullary osmotic gradient respectively?
sets up = loop of henle
maintains it = vasa recta
What is the purposed of the countercurrent multiplication?
concentrate medullary interstitial fluid
why does the medullary interstitial fluid need concentrating?
to enable kidneys to produce urine of different volume + conc according to amounts of ADH
(dependent on bodys hydration status)
components of countercurrent system
countercurrent multiplier = loop of henle
countercurrent exchanger = vasa recta
does ADH increase or decrease urine production?
decreases -> ANTIdiuretic
conserves water
aldosterone increases the absorption + secretion of what respectively?
increases Na reabsorption
increases K/H secretion
–> (spironolactone can cause hyperkalaemia)
affect of atrial netriuretic hormone
decrease Na reabsorption
opposite to aldosterone
effect of PTH on Ca + phosphate
increases Ca reabsorption
decreases phosphate reabsorption
where is the Na-K-2Cl triple cotransporter present?
thick ascending loop
–> blocked by loop diuretics
the inhibitory effect of parathyroid hormone on renal phosphate reabsorption.
At what site in the kidney is parathyroid hormone likely to be having the greatest effect to cause these blood results?
Proximal convoluted tubule
-> Majority of renal phosphate reabsorption occurs in the proximal convoluted tubule
(why parathyroid hormone is having greatest effect here)
