Download Lab Exer 8 Renal Regulation of Fluid and Electrolyte Balance

Laboratory Exercise 8: Renal Regulation of Fluid and Electrolyte Balance
The kidneys’ ability to maintain constancy of the internal environment (homeostasis) can be
demonstrated when the blood is diluted or concentrated. When a water load is taken by person, it
represents a threat to homeostasis that involves a diuretic response. When a salt load is taken by a
person, it creates a need to conserve water and increase rate of salt excretion. The water-to-salt ratio
must be kept within normal limits by compensatory changes.
During strenuous exercise the circulatory system senses that increasing blood flow to the skeletal
muscles is a higher priority than a steady supply to the kidneys. Blood to the kidneys is thus decreased
and the glomerular filtration rate drops.
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Questions: If three subjects ingest the same volume of three different solutions, will the percentage of
NaCl in the solution affect the specific gravity and rate of urine production? If so, and in what way?
Answer: Yes, the percent of NaCl will affect specific gravity of the urine and rate of urine production
to maintain homeostatic salt to water balance in the body.
Increase percent of NaCl ingested increases specific gravity and decreases rate of urine production;
because salt holds water and the hormone ADH increases the permeability of the cells of the collecting
ducts to water reabsorption. After a time as the salt is excreted in the urine then water will follow by
osmosis and the rate of urine production will increase and specific gravity will decrease.
Hypothesis: Volume of urine is dependent on the concentration of NaCl ingested.
Subject 1 drank isotonic (0.9%) NaCl solution.
Subject 2 drank hypotonic (distilled H2O) solution.
Subject 3 drank hypertonic (5% NaCl) solution.
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