Renal Physiology

Updated 2007-04-05 07:50


Notes about Renal Physiology.


Percent of total body weight that is total body water60%
TBW is highest inneborns and adult males
TBW is lowest inadult females and adults with large amounts of adipose tissue
ICF comprises how much of TBW2/3
major cations of ICFK+ and Mg2+
major anions of ICFprotein and organic phosphates
ECF comprises how much of TBW1/3
ECF is composed ofinterstitial fluid and plasma
major cation of ECFNa+
major anions of ECFCl- and HCO3-
how much of ECF is plasma?1/4
how much of ECF is interstitial fluid?3/4
an ultrafiltrate of plasma (has little protein)interstitial fluid
steady state osmolarities of ECF and ICFequal
how equality between compartments is achievedwater shifts
isomotic volume expansionincrease in ECF volume; decrease in hematocrit
isomotic volume contractiondecrease in ECF volume; increase in hematocrit
hyperosmotic volume expansionincrease in ECF volume, ECF Osmolarity, serum Na+ conc.; decrease in ICF volume, hematocrit
hyperosmotic volume contractionincrease in ECF osmolarity, serum Na+ conc.;decrease in ECF volume, ICF volume,
hypoosmotic volume expansionincrease in ECF volume, ICF volume; decrease in ECF osmolarity, serum Na+
hypoosmotic volume contractionincrease in ICF volume, hematocrit; decrease in ECF volume, ECF osmolarity, serum Na+
clearancevolume of plasma cleared of a substance per unit time
clearance equationC=U*V/P
RBF is what percent of cardiac output25%
RBF is directly proportional topressure difference between renal artery and renal vein
RBF is inversely proportional toresistance of the renal vasulature
vasoconstriction of renal arterioles does thisdecrease RBF
causes vasoconstrictionsympathetic nervous system and angiotensin II
at low concentrations angiotensin II preferentially constrictsefferent arterioles
constriction of efferent arteriolesincreases GFR
ACE inhibitorsdilate efferent arterioles, reduce hyperfiltration and occurence of diabetic nephropathy
vasodilation of renal arterioles does thisincrease RBF


Question Answer
produce vasodilationprostaglandins E2 and I2, bradykinin, nitric oxide, dopamine
how RBF is maintainedchanging renal vascular resistance
range of blood pressures in which RBF remains constant80-200
myogenic mechanismrenal afferent arterioles contract in response to stretch
tuboglomerular feedbackmacula densa sense increased load and cause constriction of afferent arterioles
used to measure RPFclearance of PAH
PAH ispara-aminohippuric acid
PAH underestimates RBF by10%
measurement of RBFRBF = RPF/(1-HCT)
used to measure GFRclearance of Inulin
filtration fractionGFR/RPF
normal filtratoin fraction0.2
if filtration fraction increasesprotein concentration in blood in peritubular capillaries increases and reabsorption increases in the proximal tubule
if filtration fraction decreasesprotein concentration in blood in the peritubuar capillaries decreases and reabsorption decreases in the proximal tubule
glomerular hydrostatic pressureincreased by dilation of afferent arterioles and constriction of efferent arterioles
increase in glomerular hydrostatic pressure causesincrease in GFR
GFR equationGFR=Kf[(Pgc-Pbs)-(PIgc-PIbs)]
Filtered loadGFR*[Plasma]
Excretion rate[Urine]*V
Reabsorption Ratefiltered load - excretion rate
secretion rateexcretion rate - filtered load
reabsorbs glucose from tubular fluid into bloodNA+-glucose cotransport in the proximal tubule
reabsorptive rate at which the carriers are saturatedTm
Tm for glucose (no reabsorption)350
plasma concentration at which glucose first appears in the urinethreshold
threshold for glucose250
region between threshold and Tmsplay
where secretion of PAH occursproximal tubule
substances with highest clearancesfiltered and secreted
substances with lowest clearancesnot filtered or completely reabsorbed
substances with clearance equal to GFRfreely filtered but not reabsorbed or secreted
Clearance RatioCx/GFR
Na+ is removed herealong entire nephron

Concepts II

Question Answer
how much Na+ is reabsorbed in the proximal tubule67%
Na+ is reabsorbed in early proximal tubule via cotransport withglucose, phosphate, amino acids, and lactate
Na+ is reabsorbed in early proximal tubule via countertransport withH+
acetazolamidecarbonic anydrase inhibitor
NA+ is reabsorbed in late proximal tubule via cotransport withCl-
glomerulotubular balance in proximal tubuleconstant fractional reabsorption of Na+ and H2O
ECF volume contraction causesincrease in proximal tubular reabsorption
ECF volume expanstion causesdecrease in proximal tubular reabsorption
how much Na+ is reabsorbed in thick ascending limb of loop of Henle25%
mechanism of Na+ reabsorption in thick ascending limbNa+-K+-2Cl- cotransporter
loop diuretics inhibitNa+-K+-2Cl- cotransporter
furosemideloop diuretic
ethacrynic acidloop diuretic
bumetanideloop diuretic
true or false: thick ascending limb is permeable to waterfalse
potential difference in thick ascending limblumen-positive potential difference
how much of Na+ is reabsorbed in the distal tubule and collecting duct8%
reabsorption of Na+ in early distal tubuleNa+-Cl- cotransporter
thiazide diuretics inhibitNa+-Cl- cotransporter in early distal tubule
true or false: early distal tubule is impermeable to watertrue
two cell types in late distal tubule and collecting ductprincipal cells and alpha-intercalated cells
principal cell reabsorbNa+ and H2O
principal cells secreteK+
effect of aldosterone on principal cellsincrease Na+ reabsorption and K+ secretion
effect of ADH on principal cellsincrease H2O permeability
K+-sparing diureticsdecrease K+ secretion
spironolactoneK+-sparing diuretic
triamtereneK+-sparing diuretic
amilorideK+-sparing diuretic
alpha-intercalated cells secreteH+
alpha-intercalated cells reabsorbK+ via H+,K+-ATPase


Question Answer
effect of aldosterone on alpha-intercalated cellsincrease H+ secretion
location of most of body's K+ICF
shift of K+ out of cells causeshyperkalemia
shift of K+ into cells causeshypokalemia
when K+ excretion equals K+ dietary intakeK+ balance
filtration of K+occurs freely
how much K+ is reabsorbed across proximal tubule67%
how much K+ is reabsorbed across thick ascending limb20%
reabsorption of K+ in thick ascending limb is done viaNa+-K+-2Cl- cotransporter
action of K+ in distal tubule and collecting ducteither secreted or reabsorbed
hyperaldosteronismincreases K+ secretion and causes hypokalemia
hypoalsosteronismdecreases K+ secretion and causes hyperkalemia
effect of acidosis on K+ secretiondecreases
effect of alkalosis on K+ secretionincreases
effect of thiazide and loop diuretics on K+ secretionincreases
effect of excess of anions in the lumen on K+ secretionincreases
how much of the filtered urea is reabsorbed in proximal tubule50%
impermeable to ureadistal tubule, cortical and outer medullary collecting ducts
effect of ADH on ureaincreases permeability in inner medullary collecting ducts
how does urea excretion vary with urine flow rateinversely
how much of phosphate is reabsorbed in the proximal tubule85%
how is phophate reabsorbed in proximal tubulevia Na+-phosphate cotransport
true or false: distal segments do not reabsorb phosphatetrue
effect of PTH on phosphate reabsorptioninhibits
how much of plasma Ca+ is filtered across glomerular capillaries60%
how much of filtered Ca+ is reabsorbed in proximal tubule and thick ascending limb90%
effect of loop diuretics on Ca+ reabsorptioninhibits
how much of filtered Ca+ is reabsorbed in the distal tubule and collecting ducts8%
effect of thiazide diuretics on Ca+ reabsorptionincreases
where is Mg+ reabsorbedproximal tubule, thick ascending limb, distal tubule
where do Mg+ and Ca+ compete for reabsorptionthick ascending limb
what happens to urine when ADH levels are high?becomes concentrated
effect of ADH on NaCl reabsorption in thick ascending limbincreases

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