click below
click below
Normal Size Small Size show me how
USMLE
Renal Physiology 1
Question | Answer |
---|---|
clearance of any substance = ? | urinary excretion/plasma concentration |
what does the clearance of PAH equal? | effective renal plasma flow (unless the secreting mechanism is saturated) |
what kind of diuretics are contraindicated in renal failure? Why? | potassium sparing exacerbates elevated serum potassium & hyperkalemia can lead to arrhythmia |
tubular fluid with lowest osmolarity is found where? | macula densa |
how is interstitial fluid volume related to inulin space? | inulin space approximates ECF volume, so interstitial fluid volume = inulin space - plasma volume |
what percent of total body weight is total body water? | 60% |
what proportion of total body water is ECF and ICF? | 1/3 ECF 2/3 ICF |
what percent of ECF is plasma volume? interstitial volume? | 1/4 plasma volume 3/4 interstitial volume |
how is plasma volume measured? | radiolabeled albumin |
how is extracellular volume measured? | inulin |
formula for clearance? | C=UV/P (urine concentration x urine flow rate / plasma concentration) |
what forms the size barrier of the glomerulus? | fenestrated capillary endothelium |
what formes the negative charge barrier of the glomerulus? | fused basement membrane with heparan sulfate |
what is lost in nephrotic syndrome? | charge barrier results in albuminuria, hypoproteinemia, generalized edema, and hyperlipidemia |
what substance is used to calculate GFR? | inulin |
creatinine clearance is an approximate measure of what? | GFR |
what does renal blood flow equal? | renal plasma flow/1-Hct |
effective renal plasma flow underestimates true renal plasma flow by how much? | about 10% |
filtration fraction = ? | GFR/RPF |
what arteriole does AT II act on? | preferentially constricts efferent arteriole decreases RPF, increases GFR, so FF increases |
what dilates the afferent arteriole? what effect does this have? | prostaglandins increases RPF, GFR so FF remains constant |
afferent arteriole constriction has what effect? | decreases RPF & GFR, so FF remains constant |
efferent arteriole constriction has what effect? | decreases RPF, increases GFR, so FF increases |
increased plasma protein concentration has what effect on GFR? | decreases GFR, (RPF stays same so FF decreases) |
decreased plasma protein concentration has what effect on GFR? | increases GFR (RPF stays same, so FF increases) |
constriction of ureter has what effect on GFR? | decreases it (also decreases FF) |
free water clearance = ? | urine flow rate - clearance(osm) |
at what plasma glucose level does glucosuria begin? at what level does the transport mechanism become saturated? | glucosuria: 200 transtport sat: 350 |
the osmolarity of the medulla can reach what level? | 1200 mOsm |
on what type of cells does aldosterone act? | principal cells of collecting ducts - activates Na+/K+ pump; intercalated cells - stimulates H+ secretion |
portion of the nephron that reabsorbs all of the glucose & AAs, and most of the bicarbonate, sodium, and water; secretes ammonia, which acts as a buffer for H+ | early proximal convoluted tubule |
portion of the nephron that passively reabsorbs water via medullary hypertonicity | thin descending limb |
portion of the nephron that contains the NKCC and indirectly induces the absorption of Mg2+ and Ca2+; impermeable to water | thick ascending limb |
location of the nephron in which calcium reabsorption is under the control of PTH? | early distal convoluted tubule |
actions of the early distal convoluted tubule? | actively reabsorbs Na+, Cl-; reabsorbs calcium under PTH control |
portion of the nephron that reabsorbs sodium in exchange for secreting potassium or H+? what regulates this? | collecting tubules aldosterone |
reabsorption of water in this portion of the nephron is under control of ADH (vasopressin) | collecting tubules |