Rivka played beach volleyball on a hot day without drinking water and became dehydrated. Her body stopped sweating and she felt dizzy. When in a state of dehydration, the kidneys' glomerular filtration rate decreases due to low blood pressure. The juxtaglomerular apparatus would secrete renin to constrict the afferent arteriole and raise the glomerular filtration rate. Aldosterone increases sodium reabsorption in the distal convoluted tubule, which would help Rivka restore her sodium and water levels. A specific gravity test of Rivka's urine would likely show a higher than normal level, indicating her kidneys were concentrating her urine due to dehydration

1. Case Study 2
Structure and Function of the Kidney
Rivka is an active 21-year-old who decided to take a day off
from her university classes. The weather was hot and the sun
bright, so she decided to go down to the beach. When she
arrived, she found a few people playing beach volleyball, and
they asked if she wanted to join in. She put down her school bag
and began to play. The others were well prepared for their day
out and stopped throughout the game to have their power drinks
and soda pop. Several hours after they began to play, however,
Rivka was not feeling so good. She stopped sweating and was
feeling dizzy. One player noted she had not taken a washroom
break at all during the day. They found a shaded area for her,
and one of the players shared his power drink with her. Rivka
was thirstier than she realized and quickly finished the drink.
In pronounced dehydration, hypotension can occur. How would
this affect the glomerular filtration rate of the kidney? What
actions by the juxtaglomerular apparatus would occur to restore
GFR?
What is the effect aldosterone has on the distal convoluted
tubule? Why would the actions of aldosterone be useful to
Rivka in her situation?
What does a specific gravity test measure? If someone tested
the specific gravity of Rivka’s urine, what might it indicate?