the loop of henle

Question 1

what happens at the ascending limb?

Answer 1

• Na+ and Cl- pumped OUT
• by active transport (using ATP)
• so water potential of medulla decreases
• water cannot move out by osmosis as ascending limb is impermeable to water

Question 2

what happens at the descending limb?

Answer 2

• is permeable to water so H2O moves out by osmosis
• water is absorbed into capillaries
• increasing concentration of urine

Question 3

what happens at the collecting duct?

Answer 3

• ADH changes its permeability to water
• more ADH = more water moves out of collecting duct into the medulla = less piss (because less water inside the collecting duct)

Question 4

what is the effect of a longer loop of henle?

Answer 4

the longer the loop of Henle, the more concentrated the medulla because more water is reabsorbed (out of the collecting duct)

so the urine produced is more concentrated