Pack 23 - Loop of Henle and Maintenance of Na+ ion gradient

Question 1

What happens to Na+ ions near the top of the ascending limb?

Answer 1

They are pumped out via active transport.

Question 2

What happens to sodium ions at the bottom of the ascending limb?

Answer 2

They are pumped out via diffusion due to a high concentration of Na+ ions in filtrate

Question 3

Why can’t water leave the ascending limb?

Answer 3

Because it is impermeable

Question 4

Is there a low water potential gradient or a high water potential gradient in the medulla?

Answer 4

Low water potential gradient as there is a higher concentration of Na+ in the tissue fluid

Question 5

Is the descending limb impermeable to water or Na+ ions?

Answer 5

Na+ ions

Question 5

Is the descending limb impermeable to water or Na+ ions?

Answer 5

Na+ ions which means water leaves the descending limb via osmosis, reducing the water potential gradient within the limb as Na+ ions can’t leave

Question 6

What happens to the water within the tissue fluid of the medulla?

Answer 6

Reabsorbed into vasa recta by osmosis

Question 7

How is water reabsorbed from the collecting ducts?

Answer 7

Loop of Henle creates a sodium ion gradient which means a lower water potential which then means water moves into the tissue fluid via osmosis (from the collecting duct)

Question 8

Why could a longer loop of Henle be beneficial?

Answer 8

The deeper the loop goes the more Na+ ions in the ascending limb will be pushed out into the tissue fluid of the medulla via active transport and diffusion, and also the more water from the descending limb will move out into the tissue fluid.
Build up a large low water potential around ‘apex’ of loop (top of loop)

Question 9

What happens to water in the descending limb, and what does this mean for the water potential in the limb?

Answer 9

Water moves out via osmosis into the tissue fluid of the medulla as the limb is permeable to water
Lower water potential as there is a high concentration of Na+ in the limb