lecture 33

Question 1

what drives and regulates body water homeostasis?

Answer 1

distribution of water
osmolarity/tonicity
reabsorption
effects of osmotic and volume changes

Question 2

what portion of out body is water?

Answer 2

55-60%

Question 3

what portion of total body water is ICF?

Answer 3

2/3

Question 4

what portion of total body water is ECF?

Answer 4

1/3

Question 5

What portion of ECF is plasma?

Answer 5

1/5

Question 6

what portion of ECF is interstitial fluid?

Answer 6

4/5

Question 7

what is osmolarity based on?

Answer 7

osmotically active ions or solutes

Question 8

hypo-osmolarity?

Answer 8

lower than usual

Question 9

what is tonicity?

Answer 9

the effect of a solution on cells

Question 10

ECF concentration of Na+ and K+?

Answer 10

145 and 4-5mmol/L respectively

Question 11

ICF concentration of Na+ and K+?

Answer 11

15 and 150mmol/L respectively

Question 12

what is adjusted to maintain intake and loss of water?

Answer 12

urine output

Question 13

how much sodium is filtered load is reabsorbed in the PCT?

Answer 13

67%

Question 14

how much sodium is filtered load is reabsorbed in the thick ascending limb?

Answer 14

25% and only sodium

Question 15

what percent of sodium in the filtered load is reabsorbed at the DCT?

Answer 15

5%

Question 16

how much sodium is filtered load is reabsorbed at the collecting duct?

Answer 16

3%

Question 17

what are the three important places within the nephron where water is reabsorbed?

Answer 17

PCT - 67%
tDLH - 25%
CD - 8%

Question 18

what is water reabsorption in the PCT driven by?

Answer 18

Na+ reabsorption (isosmotic)

Question 19

why does the thin ascending limb reabsorb water in the nephron loop?

Answer 19

it has leaky epithelium facilitation water reabsorption via aquaporins and paracellular pathway

Question 20

water reabsorption in the kidney is mainly facilitated by?

Answer 20

glucose reabsorption

Question 21

what proportion of water reabsorption does obligatory account for?

Answer 21

92% and not regulated

Question 22

why does facultative water reabsorption only account for 2-8% of water reabsorption?

Answer 22

tight epithelia
only trans cellular
regulated by ADH

Question 23

what changes osmolarity?

Answer 23

changing water content, fluid shifts between ECF-ICF to equalise change

Question 24

what are repercussions of changes in osmolarity?

Answer 24

cell structure can be altered leading to cell functions becoming impaired

Question 25

what detects changes in total body water?

Answer 25

osmoreceptors in hypothalamus

Question 26

what is the response to low or high plasma osmolarity?

Answer 26

stimulation of pituitary gland to secrete more or less ADH

Question 27

what does ADH do?

Answer 27

alters permeability of renal collecting duct

Question 28

what is diuresis?

Answer 28

high urine volume because water is not being reabsorbed in CD

Question 29

how does ADH affect the cell?

Answer 29

binds to receptor on basolateral side of collecting duct cells and increases amount of aquaporins in apical membrane

Question 30

what senses changes in sodium reaching DCT?

Answer 30

macula dense cells

Question 31

if the sodium reaching DCT is too low what happens?

Answer 31

renin is released from juxtaglomerular cells

Question 32

what is the receptor that promotes sympathetic activation for low ECF volume?

Answer 32

barorecpotrs

Question 33

what are the results of renin release from kidney?

Answer 33

decreased Na+ and water lost in urine