L27 - Regulation Of Water And Salts

Question 1

Where does Na+ reabsorption occur? (3)

Answer 1

• proximal tubule
• ascending loop of henle
• collecting ducts

Question 2

How is Na+ reabsorbed from tubule to cell in the PCT?

Answer 2

Na+ moved from tubules into cells

Question 3

How is Na+ reabsorbed from cell to body in the PCT? (2)

Answer 3

• Na+ moved from cells to intersitial space and then blood via active transport
• K+ returns to interstitial fluid via ion channels

Question 4

What two ways does Na+ move from tubules into cells in the PCT?

Answer 4

• co-transport with other molecules
• counter-transport of H ions

Question 5

What does the Na+/K+ ATPase pump require?

Answer 5

ATP

Question 6

How does K+ return to interstitial fluid via ion channels?

Answer 6

Down concentration gradient

Question 7

How is Na+ reabsorbed from the tubule to cell in the ascending loop of henle? (3)

Answer 7

• Na+ moved from tubules into cells through cotransport of K+ and Cl-
• Na-K-Cl contransporter (NKCC)
• K+ moves back into tubule via ion channels

Question 8

How is Na+ reabsorbed from the cell to the body in the ascending loop of henle? (2)

Answer 8

• Na+/K+ATPase moves Na+ out to interstitial space and K+ into cells
• K+ returns to intersitial fluid via ion channels

Question 9

How is Na+ reabsorbed from the tubule to cell in the collecting ducts? (2)

Answer 9

• Na+ moves into cell
• K+ moves out through ion channel

Question 10

How is Na+ reabsorbed from the cell to the body in the collecting ducts?

Answer 10

Na+/K+ATPase moves Na+ out to interstitial space and K+ into cells

Question 11

What is aldosterone?

Answer 11

Steroid hormone

Question 12

What does aldosterone do? (3)

Answer 12

• regulates Na+ reabsorption and blood pressure
• acts in collecting duct tubule cells
• increases expression of ion channel and Na+/K+ATPase

Question 13

Where is water reabsorbed? (2)

Answer 13

• descending loop of henle
• collecting duct

Question 14

What are the main features of the water reabsorption in the loop of henle? (2)

Answer 14

• only descending loop permeant to water
• ascending loop reabsorbs salts = hypertonic solution in interstitial fluid around loop
  = water diffuses out of descending loop

Question 15

What is the blood supply like for the water reabsorption in the loop of henle? (3)

Answer 15

• blood counter to flow of loop of henle
• freshly filtered blood first encounters ascending loop of henle = salt absorption
• water from descending loop moves into blood as salt rich blood

Question 16

How is water reabsorbed in the collecting ducts? (2)

Answer 16

• collecting duct tubule cells contain lots of water channels (aquaporins)
• intersitial space full of salt from Na+ reabsorption
  = free flow of water out of tubule, through cell into interstitial space

Question 17

What is vasopressin?

Answer 17

Hormone that controls water reabsorption

Question 18

What does vasopressin do in the water reabsorption in the collecting ducts? (2)

Answer 18

• acts on receptors of collecting duct cells = aquaporin rich vesicles fuse with cell membrane
• increases number of aquaporins that water can use to cross into body