Your kidney regulate the chemical composition of body fluids by removing
metabolic wastes and retaining the proper amounts of water, salts, and nutrients. Waste is
removed from the body by the kidneys in the form of urine. Your kidneys produce
approximately 1ml of urine per min, and maintain an average ECF osmolarity of
300mosmoles/L. The purpose of this lab was to observe and measure the affects of different
substances on the kidney.
Four different people from each group were chosen to consume one of the following
800 ml of delicious tap water
800 ml of 0.9 % NaCl.
80 ml of 9 % NaCl.
800 ml of a heavily caffeinated soft drink(Mt Dew).
At 40 and 80 minute intervals after consuming the drink, each person was to go to the
bathroom and collect all of their urine in a beaker. After collecting their urine sample,
the urine flow rate was determined for each of the four samples. The urine flow rate was
determined by taking the total volume of urine collected, which was measured using a
graduated cylinder, and dividing it by 40 for the first interval, and 80 for the second
interval (ml/min). The osmolarity of the urine samples was also collected using the
freezing point depression osmometer.
Effects of NaCl on the Kidney -
The hypothalamus detects changes in the amount of water present in the
blood. If there is too little water (the blood is too concentrated) it tells the
pituitary gland to secrete ADH. This hormone has an effect on the kidney, ADH makes
the kidney re-absorb water from the ultra-filtrate. Higher levels of ADH make the
kidney work harder to reabsorb more and more water. This results in the production
of very small quantities of very concentrated urine.
Effects of Water on the Kindey -
The hypothalamus detects that there is too much water in the blood. When the blood
becomes too dilute, the pituitary glands stop making ADH, and the kidney stops reabsorbing
water. Large volumes of very dilute urine are formed.
Effects of Mt. Dew on the Kidney -
Mountain Dew is a highly caffinated drink and acts as a diuretic which makes you produce
lots of urine and this results in your blood becoming very concentrated.