5.1.2 (d) Osmoregulation

Question 1

what is osmoregulation?

Answer 1

controlling of water potential in the blood within narrow boundaries

Question 2

what hormone controls the amount of water in the urine?

Answer 2

ADH in a negative feedback system

Question 3

where is ADH produced?

Answer 3

in the hypothalamus

Question 4

where is ADH secreted?

Answer 4

into the POSTERIOR pituitary gland

Question 5

where does ADH affect the permeability of?

Answer 5

the distal convoluted tubule
the collecting duct

Question 6

what is ADH carried in to get to the kidney tubule cells?

Answer 6

the blood

Question 7

outline ADH action

Answer 7

released from posterior pituitary gland

travels in the blood to tubule cells in the kidney

binds to receptors on the cell surface membrane

causes a cascade reaction to form cAMP which acts as a secondary messenger

cAMP stimulates vesicles containing aquaporins to fuse with the cells surface membrane

this increases the permeability

Question 8

what does ADH do when it binds to the receptors on the cell surface membrane of kidney tubule cells?

Answer 8

triggers the formation of cAMP which acts as a secondary messenger

Question 9

how does cAMP act as a secondary messenger?

Answer 9

causes vesicles containing aquaporins to fuse with the cell surface membrane of cells which line the DCT and collecting duct which increases it’s permeability to water

water moves out of the collecting duct/DCT into the medulla

Question 10

what happens when more ADH is secreted?

Answer 10

more aquaporins are formed in the cell surface membrane
SO MORE PERMEABLE

Question 11

what happens when less ADH is secreted?

Answer 11

aquaporins remove themselves from the cell surface membrane
SO LESS PERMEABLE

Question 12

concentrated urine

Answer 12

more water reabsorbed back into blood

Question 13

dilute urine

Answer 13

more water removed by excretion

Question 14

ADH and urine conc relationship

Answer 14

more ADH =concentrated urine
less ADH = dilute urine

Question 15

what detects changes in water potential in the blood?

Answer 15

osmoreceptors

Question 16

where are osmoreceptors found?

Answer 16

in the hypothalamus

Question 17

what happens to the conc of inorganic ions when water is in short supply?

Answer 17

it rises which causes the water potential to lower

this is detected by the osmoreceptors in hypothalamus and activates them

Question 18

what do the osmoreceptors send when activated and to who?

Answer 18

they send nerve impulses to the posterior pituitary gland

Question 19

what does the posterior pituitary do when there is water in short supply?

Answer 19

secrete more ADH

Question 20

what happens to the walls of the collecting duct when water is in low supply?

Answer 20

the excess ADH secreted causes more aquaporins to fuse with the cell surface membrane which increases the permeability and allows more water to move back into the blood

urine more concentrated

Question 21

what happens to the conc of inorganic ions when water is in excess?

Answer 21

decreases

osmoreceptors stimulate the posterior pituitary gland to stop secreting ADH

walls of PCT and CD become less permeable as aquaporins remove themselves

water is prevented from being reabsorbed into the blood

urine more dilute