BIOL 373: Unit 4c (Renal Function 3) || Already Graded A+.
- cardiovascular system (increase cardiac output and vasoconstriction)
- behaviour (increase thirst)
- kidneys (conserve water) correct answers What are the 3 different homeostatic reflexes that are
triggered by decreased blood volume/pressure?
Volume receptors in atria and carotid and aortic baroreceptors correct answers What senses the
stimuli of decreased blood volume/pressure?
True: this is a whole body emergency, and the priority is not renal auto regulation to increase
GFR correct answers T or F: In severe dehydration, GFR stops.
Osmolarity correct answers The _________ of urine indicates how much water is being excreted
by the kidneys.
False: The cortex is iso-osmotic to plasma, but the renal medulla becomes progressively more
concentrated the deeper it goes. correct answers T or F: The renal cortex and renal medulla are
much more concentrated than plasma
Varying amount of water and Na+ reabsorbed in the distal nephron, especially the collecting
duct. To produce dilute urine (water loss), solute is reabsorbed without letting water follow. To
concentrate urine (water retention), water is reabsorbed, but solute is left in the tubules. correct
answers How are changes in osmolarity (water loss vs retention) achieved by the kidneys?
Hypo-osmotic correct answers solution with lower osmolarity
1) In the proximal tubule, 70% of water in the filtrate will be reabsorbed, and this filtrate is iso-
osmotic to plasma (roughly equal amounts of salt and water).
2) iso-osmotic fluid leaving the proximal tubule into the descending limb becomes progressively
more concentrated, as more water is reabsorbed.
, 3) removal of solute in the thick ascending limb creates hypo-osmotic fluid, as ions are
reabsorbed but water is retained.
4) As the hypo-osmotic fluid enters the distal nephron, the levels of water and osmolarity may be
regulated by hormones (adjusting the permeability) according to the needs of the body.
5) Final urine osmolarity depends on reabsorption in the distal nephron, especially the collecting
duct. correct answers Explain how the osmolarity of the filtrate changes as it passes through the
juxtamedullary nephron.
True: therefore, more concentrated urine is able to be produced with longer loops of Henle. This
is why animals who are good at tolerating dry environments have longer loops of Henle and a
higher proportion of juxtamedullary nephrons. correct answers T or F: The longer the loop of
Henle, the saltier the filtrate can be at the bottom
Into the vasa recta (the solutes exiting from the ascending limb also enter the vasa recta) correct
answers As water is lost from the filtrate as it moves down the descending limb, where does the
water in the interstitium go?
The vasa recta takes in water that exits the descending limb, and brings this water UP, contrary to
the direction of the descending limb. Similarly, the vasa recta takes in solutes that exit the
ascending limb, and brings these solutes DOWN, contrary to the direction of the ascending limb.
This is extremely important because this maintains the salt gradient in the renal medulla (deeper
= more salty), and prevents the delution of the salt gradient. If the vasa recta was running in the
same direction, then the water it would take from the descending limb would also go down,
deeper into the medulla, and dilute it. correct answers The vasa recta runs in the opposite
direction of the fluid in the loop of Henle. Why is this important?
Aquaporins correct answers channel proteins that facilitate the passage of water
diuresis correct answers increased formation and secretion of diluted urine to eliminate excess
water
- 'leaks' through lipid bilayer (diffusion)
- cardiovascular system (increase cardiac output and vasoconstriction)
- behaviour (increase thirst)
- kidneys (conserve water) correct answers What are the 3 different homeostatic reflexes that are
triggered by decreased blood volume/pressure?
Volume receptors in atria and carotid and aortic baroreceptors correct answers What senses the
stimuli of decreased blood volume/pressure?
True: this is a whole body emergency, and the priority is not renal auto regulation to increase
GFR correct answers T or F: In severe dehydration, GFR stops.
Osmolarity correct answers The _________ of urine indicates how much water is being excreted
by the kidneys.
False: The cortex is iso-osmotic to plasma, but the renal medulla becomes progressively more
concentrated the deeper it goes. correct answers T or F: The renal cortex and renal medulla are
much more concentrated than plasma
Varying amount of water and Na+ reabsorbed in the distal nephron, especially the collecting
duct. To produce dilute urine (water loss), solute is reabsorbed without letting water follow. To
concentrate urine (water retention), water is reabsorbed, but solute is left in the tubules. correct
answers How are changes in osmolarity (water loss vs retention) achieved by the kidneys?
Hypo-osmotic correct answers solution with lower osmolarity
1) In the proximal tubule, 70% of water in the filtrate will be reabsorbed, and this filtrate is iso-
osmotic to plasma (roughly equal amounts of salt and water).
2) iso-osmotic fluid leaving the proximal tubule into the descending limb becomes progressively
more concentrated, as more water is reabsorbed.
, 3) removal of solute in the thick ascending limb creates hypo-osmotic fluid, as ions are
reabsorbed but water is retained.
4) As the hypo-osmotic fluid enters the distal nephron, the levels of water and osmolarity may be
regulated by hormones (adjusting the permeability) according to the needs of the body.
5) Final urine osmolarity depends on reabsorption in the distal nephron, especially the collecting
duct. correct answers Explain how the osmolarity of the filtrate changes as it passes through the
juxtamedullary nephron.
True: therefore, more concentrated urine is able to be produced with longer loops of Henle. This
is why animals who are good at tolerating dry environments have longer loops of Henle and a
higher proportion of juxtamedullary nephrons. correct answers T or F: The longer the loop of
Henle, the saltier the filtrate can be at the bottom
Into the vasa recta (the solutes exiting from the ascending limb also enter the vasa recta) correct
answers As water is lost from the filtrate as it moves down the descending limb, where does the
water in the interstitium go?
The vasa recta takes in water that exits the descending limb, and brings this water UP, contrary to
the direction of the descending limb. Similarly, the vasa recta takes in solutes that exit the
ascending limb, and brings these solutes DOWN, contrary to the direction of the ascending limb.
This is extremely important because this maintains the salt gradient in the renal medulla (deeper
= more salty), and prevents the delution of the salt gradient. If the vasa recta was running in the
same direction, then the water it would take from the descending limb would also go down,
deeper into the medulla, and dilute it. correct answers The vasa recta runs in the opposite
direction of the fluid in the loop of Henle. Why is this important?
Aquaporins correct answers channel proteins that facilitate the passage of water
diuresis correct answers increased formation and secretion of diluted urine to eliminate excess
water
- 'leaks' through lipid bilayer (diffusion)
