First Aid Renal Physiology Flashcards
Ureters pass under what structures?
Uterine artery (female) or vas deferens (males)
Potassium inside the cell?
High (HIKIN’ = HIgh K Intracellular)
60-40-20 rule
60% of body is water, 40% of body is ICF, 20% of body is ECF
How do you measure plasma volume?
radiolabeled albumin
How do you measure extracellular volume?
inulin
what is the osmalarity of plasma?
290
responsible for filtration of plasma according to size and net charge
glomerular filtration barrier
what is the size barrier of glomerular filtration?
fenestrated capillary endothelium
what is the negative charge barrier of glomerular filtration?
fused basement membrane with heparin sulfate
what does the epithelial layer of glomerular filtration barrier consist of?
podocyte foot processes
The charge barrier is lost in XXXX, resulting in albuminuria, hyporoteinuria, generalized edema, and hyperlipidemia
nephrotic syndrome
how do you calculate clearance?
(urine concentration x urine flow rate)/plasma concentration
when clearance is greater than GFR?
net secretion
when clearance is less than GFR?
net reabsorbtion
inulin clearance can be used to calculate GFR because it is
freely filtered and neither reabsorbed nor secreted
normal GFR =
100 ml/min
creatinine clearance slightly overestimates GFR because it is
moderately secreted by the renal tubules
ERPF can be estimated using PAH clearance because
it is both filtered and actively secreted in the proximal tubule (all PAH entering the kidney is excreted)
RBF =
RPF/(1-HCt)
EFPF underestimates true RPF by
~10%
FF =
GRF/RPF
What dilates afferent arterioles?
Prostaglandins
Prostaglandins dilate afferent arterioles –>
increased RPF, increased GFR, and no change in FF
NSAID effect on kidney
block prostaglandins –> constrict afferent artery –> decreased RPF, decreased GFR, and no change in FF
Angiotensin II preferentially constricts efferent arteriole –>
decreased RPF, increased GFR, increased FF
ACE inhibitors preferential vasodilates efferent arteriole –>
increased RPF, decreased GFR, decreased FF
what is the effect on RBF, GFR, and FF with increased plasma protein concentration
NC
Decreased
Decreased
what is the effect on RBF, GFR, and FF with decreased plasma protein concentration?
NC
Increased
Increased
what is the effect on RBF, GFR, and FF with ureter constriction?
NC
Decreased
Decreased
filtered load =
GFR x Plasma concentration
Excretion rate =
urine flow x urine concentration
reabsorption =
filtered - excreted
secretion =
excreted - filtered
Glucose at a normal plasma level is completely reabsorbed in PCT by
Na_/glucose cotransport
glucose threshold
160
glucose Tm
350
Normal pregnancy reduces absorption of what in the PCT?
amino acids and glucose
amino acid clearance
sodium dependent transporters in PCT
deficiency of neutral amino acid (tryptophan) transporter; results in pellagra
Hartup’s disease
PCT reabsorbs all glucose & AA, and most (5 things)
bicarb sodium chloride phosphate water
PCT absorption does what to tonicity?
isotonic
generated and secreted by PCT to act as a buffer for secreted H+
Ammonia
Inhibits Na+/phosphate cotransport –> phosphate excretion
PTH
PTH –> decreased phosphate by
increased excretion by decreasing reabsorption in PCT
ATII stimulates NA+/H+ exchange –>
increased sodium, water, and bicarb reabsorption, permitting contraction alkalosis
what percent of Na+ is reabsorbed in the PCT?
65-80%
thin descending loop of Henle is impermeable to
sodium (concentrating sdemgnet0
actively reabsorbs sodium, potassium, and chloride
TAL
TAL indirectly induces the paracellular reabsorption of [2 things] through (+) lumen potential generation by K+ backleak
magnesium and calcium
what percent of sodium is reabsorbed in the TAL
10-20%
what drugs work at the PCT?
ACE inhibitors,
Carbonic anhydrase inhibitors
what drugs work at the TAL?
loop diuretics
TAL is impermeable to
water
actively reabsorbs sodium and potassium –> makes urine hypotonic
early DCT
what drugs work at the early DCT?
thiazide
Effect of PTH on early DCT?
increases calcium/sodium exchange –> increased calcium reabsorption
what percent of sodium is reabsorbed in the early DCT?
5-10%
what drugs work on the collecting tubule?
K+ sparing diuretics (amiloride, triamterene, spirolactone, eplerenone)
Collecting tubules reabsorb Na+ in exchange for secreting
K+ and H+
regulates collecting tubule reabsorption of Na+ in exchange for K+ and H+ secretion
aldosterone
acts on mineralocorticoid receptor in collecting tuble–> insertion of Na+ channel on luminal side
aldosterone
acts at V2 receptor in principal cell in collecting tubule
ADH
ADH –> insertion of
aquaporin H2 channels on luminal side of principal cell in collecting tubule
percent of Na+ reabsorbed in collecting tubule
3-5%
TF/P > 1 when
solute is reabsorbed less quickly than water
TF/P = 1 when
solute and water are reabsorbed at the same rate
TF/P <1 when
solute is reabsorbed more quickly than water
tubulan inulin increases in concentration along the PCT as a result of
water reabsorption
Renin responds to three things
decreased BP, decreased Na+ delivery, increased sympathetic tone
JG cells secrete renin in response to
low BP
macula densa tells JG cells to secrete renin in response to
low Na+ (Cl-) delivery
what receptors tell JG cells to secrete renin in response to increased sympathetic tone?
beta-1
AT II has six effects
- vasoconstriction of vascular smooth muscle
- vasoconstriction of efferent arteriole
- ldosterone
- ADH
- Increased proximal tubule Na+/H+ activity
- Stimulates hypothalamus
What is the rationale of AT II preferential constriction of efferent arteriole
increase FF to preserve GFR in low-volume sttes
aldosterone is produced by
adrenal gland
aldosterone effects
- increased Na+ and Na+K+ pump insertion in principal cells
2. enhanced K+ and H_ excretion
aldosterone –> enhanced K+ secretion where?
principal cell K+ channels
aldosterone –> inc H+ secretion where
intercalated cell H+ channels
net effect of aldosterone
creats favorable Na+ gradient for Na+ and H20 reabsorption
what produces ADH?
posterior pituitary
ADH –> increased H2O channel insertion in
principal cells
net effect of ADH
increased H2O reabsorption
affects baroreceptor function; limits reflex bradycardia; helps maintain blood volume and BP
angiotensin II
angiotensinogen is produced by the
liver
angiotensinogen –> angiotensin I
Renin
angiotensin I –> angiotensin II
ACE
ACE inhibits
bradykinin
ACE is produced by the
lungs
Released from atria in response to increased volume; may act as a check on RAA system; relaxes vascular smooth muscle via cGMP, causing increased GFR and decreased renin
ANP
primarily regulates osmolarity but also responds to low blood volume, which takes precedence over osmolarity
ADH
primarily regulates blood volume;
Aldosterone
in low-volume states, what acts to protect blood volume
BOTH aldosterone and ADH
beta blocker effect on kidney
inhibit beta-1 receptors of the JGA, causing decreased renin release
released by interstitial cells in the peritubular capillary bed in response to hypoxia
EPO
what cells produce epo
renal peritubular intersitial cells
what cells convert 25-OH vitamin D to its active form
proximal tubule cells
what enzyme converts vitamin D to its active form?
1alpha hydroxylase
what stimulates 1-alpha-hydroylase production?
PTH
secreted by JG cells in response to decreased renal arterial pressure and increased renal sympathetic discharge (beta1 effect)
renin
paracrine secretion vasodilates the afferent arterioles to increase GFR
prostaglandins
NSAIDs can cause acute renal failure by inhibiting the renal production of
prostaglandins
4 kidney endocrine functions
- epo
- 1,25-(OH)2 vitamin D
- Renin
- Prostaglandins
6 hormones act on kidney
ANP, PTH, Renin, AT II, Aldosterone, ADH
Secreted in response to increased atrial pressure.
Atrial natriuretic peptide (ANP)
Causes increased GFR and increased sodium filtration with no compensatory Na+ reabsorption in distal nephron –> Na+ loss and volume loss
ANP
PTH is secreted in response to three things
decreased plasma calcium
increased plasma phosphate
decreased plasma 1.25-(OH)2 vitamin D
PTH causes increased calcium reabsorption where?
DCT
PTH causes decreased phosphate reabsorption where?
PCT?
PTH has 4 effects:
increased calcium reabsorption (DCT)
decreased phosphate reabsorption (PCT)
increased 1,25-(OH)2 vitamin D production
increased calcium and phosphate absorption from gut
Angiotensin II is synthesized in response to:
decreased BP
Renin is synthesized in response to:
decreased blood volume
Aldosterone is synthesize in response to:
decreased blood volume (via AT II)
increased [K+]
Aldosterone causes three effects
- Increased sodium reabsorption
- Increased K+ secretion
- Increased H+ secretion
Causes efferent arteriole constriction (–> inc GFR and FF) but with compensatory Na+ reabsorption in proximal and distal nephron
AT II
Preservation of renal function in low-volume state (increased FF) with simultaneous NA+ reabsorption (both proximal and distal) to decreased additional volume loss
AT II
Secreted in response to increased plasma osmolarity and decreased blood volume
ADH
Binds to receptors on principal cells –> increased number of water channel channels –> increased H2O reabsorption
ADH