5.3 Kidneys & Osmoregulation

Question 1

what is osmoregulation?

Answer 1

controlling water potential of blood within very narrow boundaries

Question 2

what sorts of things can put the osmotic stress on the body?

Answer 2

salty foods
drinking a lot
exercise
fevers
hot climates

Question 3

what could happen is kPa was not kept stable?

Answer 3

damage or even death

Question 4

what is crucial to maintaining kPa, regardless of water sources is taken in or lost?

Answer 4

changing the concentration of urine

Question 5

amount of water lost in urine is controlled by which hormone? in what sort of system?

Answer 5

ADH

negative feedback system

Question 6

ADH is produced by the hypothalamus and secreted where?

Answer 6

posterior pituitary where it is stored

Question 7

what does ADH do to the collecting duct and distal convoluted tubule?

Answer 7

changes their permeability to water

Question 8

ADH is released from pituitary and travels in the blood till it binds to receptors where?

Answer 8

on cell membrane of tubule cells

Question 9

when ADH binds it triggers the formation of what?

Answer 9

cyclic AMP

Question 10

Cyclic AMP is a second messenger, what is this?

Answer 10

a molecule relaying signals received at cell surface to molecules inside the cell

Question 11

cAMP causes vesicles in the cells lining the collecting duct to do what?

Answer 11

fuse with cell surface membranes in contact with tissue fluid of medulla

Question 12

membranes of the vesicles contain what?

Answer 12

aquaporins

Question 13

what are aquaporins?

Answer 13

protein based water channels which are inserted into the cell surface membrane making it permeable to water

Question 14

what do aquaporins provide?

Answer 14

a route for water to move out of tubule cells into tissue fluid of medulla and blood capillaries by osmosis

Question 15

the more ADH released, the more aquaporins inserted making what easier?

Answer 15

water to leave tubule cells by osmosis resulting in a small amount of concentrated urine

Question 16

when water is returned to tissue fluid and blood capillaries what does it maintain?

Answer 16

kPa

Question 17

what happens when ADH levels fall?

Answer 17

levels of cAMP fall
aquaporins removed from tubule membrane and are enclosed in vesicles
collecting duct impermeable to water
large amounts of dilute urine

Question 18

control of ADH levels is done by a negative feedback system involving which receptors?

Answer 18

osmoreceptors in the hypothalamus

Question 19

what are osmoreceptors sensitive to?

Answer 19

the concentrations of inorganic ions in the blood

Question 20

(little water) when concentration of inorganic ions in the blood increases what happens to its kPa?

Answer 20

it becomes more negative

Question 21

(little water) what detects the change in kPa?

Answer 21

osmoreceptors

Question 22

(little water) what do the osmoreceptors do?

Answer 22

send nerve impulses to posterior pituitary which releases ADH

Question 23

(little water) ADH binds to receptors on collecting duct and has what effect?

Answer 23

increases permeability to water

Question 24

(little water) water leaves filtrate and diffuses into blood by osmosis producing what?

Answer 24

small amount of concentrated urine

Question 25

(excess of water) blood becomes more dilute with an excess of water, what effect does this have on kPa?

Answer 25

less negative

Question 26

(excess of water) the change is detected by what?

Answer 26

osmoreceptors

Question 27

(excess of water) what happens to the nerve impulses to the posterior pituitary?

Answer 27

reduced or stopped and release of ADH inhibited

Question 28

(excess of water) what happens to the walls of the collecting duct?

Answer 28

remain impermeable to water little reabsorption takes place

Question 29

(excess of water) what is produced?

Answer 29

large amount of dilute urine

Question 30

what other receptors control ADH release?

Answer 30

baroreceptors

Question 31

baroreceptors in the aortic and carotid arteries detect changes in what?

Answer 31

blood pressure which can stimulate or inhibit ADH release

Question 32

(baroreceptors) increase in blood pressure can be caused by a rise in what?

Answer 32

blood vol

Question 33

(baroreceptors) increase in blood pressure is detected by baroreceptors which do what?

Answer 33

prevent release of ADH

Question 34

(baroreceptors) less ADH increases the amount of water lost in urine which has what effect?

Answer 34

reduced blood volume | reduced blood pressure

Question 35

(baroreceptors) what happens if a decrease in blood pressure and vol is detected by baroreceptors?

Answer 35

more ADH released increased permeability to water small amount of concentrated urine increase in blood vol & blood pressure