An investigator is studying patients with acute decompensated congestive heart failure. He takes measurements of a hormone released from atrial myocytes, as well as serial measurements of left atrial and left ventricular pressures. The investigator observes a positive correlation between left atrial pressures and the serum level of this hormone. Which of the following is most likely the mechanism of action of this hormone?
AIncreases potassium excretion at the collecting ducts
BConstricts afferent renal arteriole
CDecreases sodium reabsorption at the collecting tubules
DDecreases reabsorption of bicarbonate in the proximal convoluted tubules
EIncreases free water reabsorption from the distal tubules
A 72-year-old female is brought to the emergency department after being found unresponsive in her garage with an open bottle of unmarked fluid. She is confused and is unable to answer questions on arrival. Her medical history is significant for Alzheimer disease, but her family says she has no medical comorbidities. Serum analysis of this patient's blood shows a pH of 7.28 with a high anion gap. The electrolyte that is most likely significantly decreased in this patient follows which of the following concentration curves across the proximal tubule of the kidney?
ACurve C
BCurve E
CCurve B
DCurve A
ECurve D
A researcher is studying the effects of a new antihypertensive medication on urine osmolality. She first measures urine osmolality in different parts of the nephron of a healthy human control. The findings are shown below: Portion of nephron Urine osmolality (mOsmol/kg) Proximal convoluted tubule 300 Loop of Henle, descending limb 1200 Loop of Henle, ascending limb 200 Distal convoluted tubule 100 Collecting duct 600 Which of the following is the most likely explanation for the urine osmolality in the ascending limb of the loop of Henle?
AIncreased urea excretion
BIncreased transcription of water channels
CImpermeability to water
DIncreased bicarbonate reabsorption
EImpermeability to sodium
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