L27 - kidney: regulation of water & salts

Question 1

where is salt reabsorbed?

Answer 1

1. PCT
2. ascending loop of HENLE
3. collecting ducts
4. hormonal control

Question 2

where is water reabsorbed?

Answer 2

1. descending loop of henle
2. collecting ducts
3. hormonal control

Question 3

where does filtration occur?

Answer 3

glomerulus + bowman’s capsule

Question 4

how is salt reabsorbed in the PCT?

Answer 4

1. Na+ moves from tubules into cells
2. via co transport with other molecuke
3. or via counter transport of H+ ions (Na+ in, H+ out)
4. Na+ moved from tubule cells to interstitial space and then blood via AT
5. Na+/K+ ATPase pump, requires ATP
6. K+ returns to interstitial fluid via ion channels down a conc gradient

Question 5

how is salt reabsorbed in the ascending loop of henle?

Answer 5

1. Na+ moved from tubules into cells through cotransport with K+ and Cl-
2. Na-K-Cl cotransporter (NKCC)
3. K+ moves back into tubule via ion channels down a conc gradient
4. Na+/K+ ATPase moves Na+ out to interstitial space and K+ into cells
5. K+ returns to interstitial fluid via ion channels down conc gradient

Question 6

how is salt reabsorbed in collecting ducts?

Answer 6

1. Na+ moves into cell and K+ moves out through ion channel down conc gradient
2. Na+/K+ ATPase moves Na+ out to interstitial space and K+ into cells

Question 7

how salt is reabsorbed via hormonal control?

Answer 7

1. aldosterone: steroid hormone
2. regulates Na+ reabsorption and blood pressure
3. acts in collecting duct tubule cells
   4, increases expression of ion channels and Na+/K+ ATPase

Question 8

how is water reabsorbed by the descending loop of henle?

Answer 8

1. only descending loop is permeable to water
2. ascending loop reabsorbs salts and creates hypertonic solution in interstitial fluid around loop
3. causes water to diffuse out of descending loop

Question 9

water reabsorption full process in loop of henle

Answer 9

1. blood flow around LOH is counter to flow through LOH
2. filtered blood that is low in salt encounters the ascending loop
3. encouraging salt reabsorption
4. salt rich blood circulates around descending limb
5. water from descending loop moves into blood
6. maintains conc gradient

Question 10

how is water reabsorbed by collecting ducts?

Answer 10

1. collecting duct tubule cells contain water channels: aquaporins
2. interstitial space full of salt from Na+ reabsorption
3. allows free flow of water out of tubule through cell into interstitial space

Question 11

how is water reabsorbed by hormonal control (collecting ducts)?

Answer 11

1. vasopressin is a hormone that controls water reabsorption
2. acts on receptors on collecting duct cells
3. causes aquaporin rich vesicles inside cell to fuse with cell membrane
4. increases number of channels water can use to cross body