loop of henle

Question 1

what is the loop of henle responsible for

Answer 1

water being reabsorbed from the collecting duct so urine has a lower water potential than the blood

Question 2

what are the two regions of the loops of henle

Answer 2

the descending limb and ascending limb

Question 3

what is the descending limb

Answer 3

narrow, thin walls that are highly permeable to water and sodium ions

Question 4

what is the ascending limb

Answer 4

wider with thick walls, only permeable to sodium ions not water

Question 5

what does the loop of henle act as

Answer 5

counter-current multiplier

Question 6

first stage of the sequence

Answer 6

sodium ions are ACTIVELY TRANSPORTED OUT of the ascending limb into the interstitial fluid using ATP (provided by the many mitochondria in the cells of its wall)

Question 7

second stage of the sequence

Answer 7

this creates a lower water potential (high ion concentration) in the region of the medulla between the two limbs (interstitial region)

normal circumstances water would pass out of the ascending limb by osmosis, however walls are impermeable to water so very little leaves

Question 8

third stage of the sequence

Answer 8

however the walls of the descending limb are very permeable and so passes out by osmosis into the interstitial space

Question 9

forth stage of the sequence

Answer 9

the filtrate progressively loses water as it moves down the descending limb lowering its water potential

Question 10

where is the water potential the lowest

Answer 10

the tip of the hairpin

Question 11

fifth stage of the sequence

Answer 11

as it moves up the ascending limb, sodium ions are being diffused out of the filtrate and therefore developing a progressively higher water potential

Question 12

sixth stage of the sequence

Answer 12

in the interstitial space between the ascending limb and the collecting duct there is a lower water potential (sodium being pumped out ascending limb)

Question 13

seventh stage of sequence

Answer 13

the collecting duct is permeable to water so as the filtrate moves down it water passes out by osmosis

as water passes out of the filtrate it’s water potential is lowered and the water potential is also lowered in the interstitial space and so water continues to move out by osmosis

Question 14

how does the water pass out the collecting duct

Answer 14

by osmosis through channel proteins specific to water (aquaporins)

Question 15

what can alter the number of aquaporins

Answer 15

Antidiuretic hormone (ADH)