Renal Physiology
rename
Updated
2007-04-05 07:50
Concepts
| Term | Definition |
|---|---|
| Percent of total body weight that is total body water | 60% |
| TBW is highest in | neborns and adult males |
| TBW is lowest in | adult females and adults with large amounts of adipose tissue |
| ICF comprises how much of TBW | 2/3 |
| major cations of ICF | K+ and Mg2+ |
| major anions of ICF | protein and organic phosphates |
| ECF comprises how much of TBW | 1/3 |
| ECF is composed of | interstitial fluid and plasma |
| major cation of ECF | Na+ |
| major anions of ECF | Cl- 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 ICF | equal |
| how equality between compartments is achieved | water shifts |
| isomotic volume expansion | increase in ECF volume; decrease in hematocrit |
| isomotic volume contraction | decrease in ECF volume; increase in hematocrit |
| hyperosmotic volume expansion | increase in ECF volume, ECF Osmolarity, serum Na+ conc.; decrease in ICF volume, hematocrit |
| hyperosmotic volume contraction | increase in ECF osmolarity, serum Na+ conc.;decrease in ECF volume, ICF volume, |
| hypoosmotic volume expansion | increase in ECF volume, ICF volume; decrease in ECF osmolarity, serum Na+ |
| hypoosmotic volume contraction | increase in ICF volume, hematocrit; decrease in ECF volume, ECF osmolarity, serum Na+ |
| clearance | volume of plasma cleared of a substance per unit time |
| clearance equation | C=U*V/P |
| RBF is what percent of cardiac output | 25% |
| RBF is directly proportional to | pressure difference between renal artery and renal vein |
| RBF is inversely proportional to | resistance of the renal vasulature |
| vasoconstriction of renal arterioles does this | decrease RBF |
| causes vasoconstriction | sympathetic nervous system and angiotensin II |
| at low concentrations angiotensin II preferentially constricts | efferent arterioles |
| constriction of efferent arterioles | increases GFR |
| ACE inhibitors | dilate efferent arterioles, reduce hyperfiltration and occurence of diabetic nephropathy |
| vasodilation of renal arterioles does this | increase RBF |
More
| Question | Answer |
|---|---|
| produce vasodilation | prostaglandins E2 and I2, bradykinin, nitric oxide, dopamine |
| how RBF is maintained | changing renal vascular resistance |
| range of blood pressures in which RBF remains constant | 80-200 |
| myogenic mechanism | renal afferent arterioles contract in response to stretch |
| tuboglomerular feedback | macula densa sense increased load and cause constriction of afferent arterioles |
| used to measure RPF | clearance of PAH |
| PAH is | para-aminohippuric acid |
| PAH underestimates RBF by | 10% |
| measurement of RBF | RBF = RPF/(1-HCT) |
| used to measure GFR | clearance of Inulin |
| filtration fraction | GFR/RPF |
| normal filtratoin fraction | 0.2 |
| if filtration fraction increases | protein concentration in blood in peritubular capillaries increases and reabsorption increases in the proximal tubule |
| if filtration fraction decreases | protein concentration in blood in the peritubuar capillaries decreases and reabsorption decreases in the proximal tubule |
| glomerular hydrostatic pressure | increased by dilation of afferent arterioles and constriction of efferent arterioles |
| increase in glomerular hydrostatic pressure causes | increase in GFR |
| GFR equation | GFR=Kf[(Pgc-Pbs)-(PIgc-PIbs)] |
| Filtered load | GFR*[Plasma] |
| Excretion rate | [Urine]*V |
| Reabsorption Rate | filtered load - excretion rate |
| secretion rate | excretion rate - filtered load |
| reabsorbs glucose from tubular fluid into blood | NA+-glucose cotransport in the proximal tubule |
| reabsorptive rate at which the carriers are saturated | Tm |
| Tm for glucose (no reabsorption) | 350 |
| plasma concentration at which glucose first appears in the urine | threshold |
| threshold for glucose | 250 |
| region between threshold and Tm | splay |
| where secretion of PAH occurs | proximal tubule |
| substances with highest clearances | filtered and secreted |
| substances with lowest clearances | not filtered or completely reabsorbed |
| substances with clearance equal to GFR | freely filtered but not reabsorbed or secreted |
| Clearance Ratio | Cx/GFR |
| Na+ is removed here | along entire nephron |
Concepts II
| Question | Answer |
|---|---|
| how much Na+ is reabsorbed in the proximal tubule | 67% |
| Na+ is reabsorbed in early proximal tubule via cotransport with | glucose, phosphate, amino acids, and lactate |
| Na+ is reabsorbed in early proximal tubule via countertransport with | H+ |
| acetazolamide | carbonic anydrase inhibitor |
| NA+ is reabsorbed in late proximal tubule via cotransport with | Cl- |
| glomerulotubular balance in proximal tubule | constant fractional reabsorption of Na+ and H2O |
| ECF volume contraction causes | increase in proximal tubular reabsorption |
| ECF volume expanstion causes | decrease in proximal tubular reabsorption |
| how much Na+ is reabsorbed in thick ascending limb of loop of Henle | 25% |
| mechanism of Na+ reabsorption in thick ascending limb | Na+-K+-2Cl- cotransporter |
| loop diuretics inhibit | Na+-K+-2Cl- cotransporter |
| furosemide | loop diuretic |
| ethacrynic acid | loop diuretic |
| bumetanide | loop diuretic |
| true or false: thick ascending limb is permeable to water | false |
| potential difference in thick ascending limb | lumen-positive potential difference |
| how much of Na+ is reabsorbed in the distal tubule and collecting duct | 8% |
| reabsorption of Na+ in early distal tubule | Na+-Cl- cotransporter |
| thiazide diuretics inhibit | Na+-Cl- cotransporter in early distal tubule |
| true or false: early distal tubule is impermeable to water | true |
| two cell types in late distal tubule and collecting duct | principal cells and alpha-intercalated cells |
| principal cell reabsorb | Na+ and H2O |
| principal cells secrete | K+ |
| effect of aldosterone on principal cells | increase Na+ reabsorption and K+ secretion |
| effect of ADH on principal cells | increase H2O permeability |
| K+-sparing diuretics | decrease K+ secretion |
| spironolactone | K+-sparing diuretic |
| triamterene | K+-sparing diuretic |
| amiloride | K+-sparing diuretic |
| alpha-intercalated cells secrete | H+ |
| alpha-intercalated cells reabsorb | K+ via H+,K+-ATPase |
More
| Question | Answer |
|---|---|
| effect of aldosterone on alpha-intercalated cells | increase H+ secretion |
| location of most of body's K+ | ICF |
| shift of K+ out of cells causes | hyperkalemia |
| shift of K+ into cells causes | hypokalemia |
| when K+ excretion equals K+ dietary intake | K+ balance |
| filtration of K+ | occurs freely |
| how much K+ is reabsorbed across proximal tubule | 67% |
| how much K+ is reabsorbed across thick ascending limb | 20% |
| reabsorption of K+ in thick ascending limb is done via | Na+-K+-2Cl- cotransporter |
| action of K+ in distal tubule and collecting duct | either secreted or reabsorbed |
| hyperaldosteronism | increases K+ secretion and causes hypokalemia |
| hypoalsosteronism | decreases K+ secretion and causes hyperkalemia |
| effect of acidosis on K+ secretion | decreases |
| effect of alkalosis on K+ secretion | increases |
| effect of thiazide and loop diuretics on K+ secretion | increases |
| effect of excess of anions in the lumen on K+ secretion | increases |
| how much of the filtered urea is reabsorbed in proximal tubule | 50% |
| impermeable to urea | distal tubule, cortical and outer medullary collecting ducts |
| effect of ADH on urea | increases permeability in inner medullary collecting ducts |
| how does urea excretion vary with urine flow rate | inversely |
| how much of phosphate is reabsorbed in the proximal tubule | 85% |
| how is phophate reabsorbed in proximal tubule | via Na+-phosphate cotransport |
| true or false: distal segments do not reabsorb phosphate | true |
| effect of PTH on phosphate reabsorption | inhibits |
| how much of plasma Ca+ is filtered across glomerular capillaries | 60% |
| how much of filtered Ca+ is reabsorbed in proximal tubule and thick ascending limb | 90% |
| effect of loop diuretics on Ca+ reabsorption | inhibits |
| how much of filtered Ca+ is reabsorbed in the distal tubule and collecting ducts | 8% |
| effect of thiazide diuretics on Ca+ reabsorption | increases |
| where is Mg+ reabsorbed | proximal tubule, thick ascending limb, distal tubule |
| where do Mg+ and Ca+ compete for reabsorption | thick ascending limb |
| what happens to urine when ADH levels are high? | becomes concentrated |
| effect of ADH on NaCl reabsorption in thick ascending limb | increases |
