Lab Exer 8 Renal Regulation of Fluid and Electrolyte Balance

L aboratory 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.

1 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.