Reg of Body Fluid Osmolarity (Rao)

Question 1

size order of output of water

Answer 1

urine&raquo_space; breathing ~ skin > feces

Question 2

size order of input of water

Answer 2

Drinking&raquo_space;> food > metabolism

Question 3

Osmoreceptors (location, effect)

Answer 3

hypothalamus, secrete AVP/ADH

Question 4

Arginine-Vasopressin (AVP)/Antidiuretic Hormone (ADH)

Receptor location & name

Answer 4

V1/V2 receptors on apical surface of renal collecting duct epithelium
Also vasoconstricts arterioles, reducing GFR

Question 5

AVP/ADH cascade

Answer 5

Secreted in hypothalamus
act on V1/V2 receptors on CD cells
activates adenylate cyclase -> cAMP synth
Protein kinase A
translocates Aquaporin 2 to luminal surface
takes 10 min

Question 6

Hyperosmotic plasma response

Answer 6

Activation of Osmoreceptors in supraoptic nucleus of hypothalamus
AVP
Excretion of hyperosmotic urine
decrease of plasma osmolarity

Also increases thirst at hypothalamus

Question 7

Incrase in ECF volume result

Answer 7

diuresis

Question 8

Severe decrease in volume (vomiting/diarrhea) result

Answer 8

increase in AVP, retention

Question 9

Cosm =

osmolar clearance

Answer 9

UF x Uosm / Posm

Normal = 1 +/- 0.5 ml/min

Question 10

Nocturia is a sign of?

Answer 10

Decreased ability to concentrate urine

Question 11

Free Water Clearance =

2 equations & definition

Answer 11

Free Water Clearance = UF - Cosm

= UF - UFxUosm/Posm

ability to concentrate urine

Question 12

Is clearing water or conserving it more efficiently done by the kidney?

Answer 12

clearing

Question 13

Transport in thin descending limb

Answer 13

+++++++ water

+ urea

Question 14

Thin ascending limb transport

Answer 14

++ NaCl (permeability)

+ urea

Question 15

Thick asending limb transport

Answer 15

NaCl (active) +++++++++

Question 16

Distal tubule transport

Answer 16

NaCl (active)

water +ADH

Question 17

Collecting duct, cortical transport

Answer 17

NaCl (active) +

water +ADH

Question 18

Collecting duct, cortical transport

Answer 18

NaCl (active) +
water +ADH
Urea ++++

Question 19

Urea contribution to medullary ISF

Answer 19

40%

Question 20

Why is medullary blood flow low?

Answer 20

to preserve high osmolarity in the medulla ISF

Question 21

Why does the vasa recta serve as a countercurrent exchanger?

Answer 21

to preserve high osmolarity in the medulla ISF

Question 22

3 causes of deficiency in kidney’s ability to concentrate or dilute urine

Answer 22

1 defect in AVP secretion
2 inability of CD to respond to AVP
3 failure to form medullary osmolarity gradient

Question 23

Diabetes Insipidus

Answer 23

High rates of production of dilute urine

Question 24

Central Diabetes Insipidus

Answer 24

pituitary gland fails to produce AVP (rare, congenital)

Question 25

Nephrogenic Diabetes Insipidus

Answer 25

CDs don’t respond to AVP
V2 receptor or aquaporin-2 mutation

Drugs: lithium, tetracycline

Question 26

4 causes of medullary hyperosmolarity loss

Answer 26

1 diuretics (furosemide, ethacrylic acid)
2 Excessive deliver of fluid into LOH
3 Decreased urea production/filtration
4 Age and renal failure (loss of nephrons)

Question 27

3 causes of deficiency in kidney’s ability to concentrate or dilute urine

Answer 27

1 defect in AVP secretion
2 inability of CD to respond to AVP
3 failure to form medullary osmolarity gradient

Question 28

Diabetes Insipidus

Answer 28

High rates of production of dilute urine

Question 29

Central Diabetes Insipidus

Answer 29

pituitary gland fails to produce AVP (rare, congenital)

Question 30

Nephrogenic Diabetes Insipidus

Answer 30

CDs don’t respond to AVP
V2 receptor or aquaporin-2 mutation

Drugs: lithium, tetracycline

Question 31

4 causes of medullary hyperosmolarity loss

Answer 31

1 diuretics (furosemide, ethacrylic acid)
2 Excessive deliver of fluid into LOH
3 Decreased urea production/filtration
4 Age and renal failure (loss of nephrons)