Ou have just admitted mary roberts, a 70-year-old woman, to the hospital for gi bleeding. her blood pressure is 130/80, pulse 80/min and irregular, respirations 18/min, and temperature 99.2. mrs. roberts denies pain at this time although she appears anxious and very pale. her medical history includes lung cancer that was diagnosed two weeks ago, peptic ulcer disease with reflux esophagitis, and "fluid retention". admission lab work shows a plasma na+ of 152 meq/l and k+ of 2.8 meq/l. which of the following regulatory mechanisms would be stimulated as a result of the increased osmolality that results from a na+ level of 152 meq/l?