Renal and Urinary Systems / Electrolyte Balance Flashcards
What is the strong ion difference?
(Na+ + K+ + Ca2+ + Mg2+) - (Cl- + other anions)
normally ~ 40-44 mEq/L
How does dehydration affect the strong ion difference?
increases it (more cations)
How can the anion gap be normal in a patient with lactic acidosis?
hypoalbuminemia
How is serum osmolality calculated?
osmolality = (2xNa) + (glucose/18) + (BUN/2.8)
What causes a difference between the measured and calculated osmolality?
the presence of substances other than sodium, glucose, and BUN
Which diuretics act in the proximal convoluted tubule?
acetazolamide
Which diuretics act in the medullary ascending loop of Henle?
furosemide
torsemide
bumetanide
mannitol
Which diuretics act in the distal convoluted tubule?
thiazides
Which diuretics act in the cortical collecting duct?
the “K-sparing” diuretics
spironolactone
amiloride
triamterene
What are the clinical uses of acetazolamide?
open angle glaucoma
treating metabolic alkalosis
preventing symptoms of acute mountain sickness
What factors cause vasoconstriction of afferent renal arterioles (decreasing GFR)?
sympathetic stimulation
angiotensin II
mesangial cell contraction
endothelin
What factors cause vasodilatation of afferent renal arterioles (increasing GFR)?
prostaglandins
nitric oxide
atrial natriuretic peptide
bradykinin
How much of the sodium filtered by the glomerulus is excreted in the urine?
about 5%
In which part in the nephron is ultrafiltrate absorbed isotonically (i.e., which part of the nephron is permeable to water)?
proximal tubule
In which part of the nephron is the urine concentrated?
medullary collecting duct
