Renal Regulation of Water and Acid/base Balance

Question 1

How is osmolarity calculated?

Answer 1

Concentration x No. of dissociated particles

Question 2

When calculating osmolarity what would be the no of dissociated particles for NaCl vs for glucose

Answer 2

NaCl= 2
Glucose= 1

Question 3

What are the units for osmolarity?

Answer 3

mOsm/L

Question 4

Are osmolarity and concentration the same? Explain why

Answer 4

No because the no of dissociated particles may be greater than one, this causes osmolarity to be greater than concantration

Question 5

What % of body weight is total fluid volume?

Answer 5

60%

Question 6

What proportion of total body fluid is extracellular vs intracellular?

Answer 6

Extracellular= 1/3
Intracellular= 2/3

Question 7

What does unregulated water loss encompass?

Answer 7

Sweat
Faeces
Vomit
Water evaporation from respiratory lining and skin

Question 8

Describe ECF vol, [Na+] and osmolarity when there is a positive water balance

Answer 8

ECF vol=high
[Na+]=low
Osmolarity=low

Question 9

Describe ECF vol, [Na+] and osmolarity when there is a negative water balance

Answer 9

ECF vol=low
[Na+]=high
Osmolarity=high

Question 10

What happens to urine production when theres a positive water balance?

Answer 10

Hypoosmotic urine production

Question 11

What happens to urine production when theres a negative water balance?

Answer 11

Hyperosmotic urine production

Question 12

What does the medullary interstitium need to be for passive water reabsorption?

Answer 12

Hyperosmotic

Question 13

How much water does the PCT reabsorb?

Answer 13

67%

Question 14

What is reabsorbed in the descending limb of the loop of Henle and how?

Answer 14

Water (passively)

Question 15

What is reabsorbed in the thin ascending limb of the loop of Henle and how?

Answer 15

NaCl (passively)

Question 16

What is reabsorbed in the thick ascending limb of the loop of Henle and how?

Answer 16

NaCl (actively)

Question 17

Describe how the counter current multiplication is set up?

Answer 17

New filtrate arrives in the loop of Henle
When it reaches the thick ascending limb sodium is actively pumped out (osmolarity in the medulla increases)
Another set of new filtrate arrives and water now passively moves out because the medulla has a greater osmolarity (the osmolarity of the fluid increases)
This hyperosmolar fluid moves down the descending limb so the osmolarity at the bottom is greater than at the top
This process continues and the gradient is set up with osmolarity higher at the bottom of the loop and lower at the top

Question 18

Where is the UT A1 transporter found?

Answer 18

Apical membrane of the collecting duct

Question 19

Where is the UT A3 transporter found?

Answer 19

Basolateral membrane of the collecting duct

Question 20

Where is the UT A2 transporter found?

Answer 20

Thin descending limb of the loop of Henle

Question 21

Where is the UT B1 transporter found?

Answer 21

Vasa recta

Question 22

What is the purpose of urea recycling? (ie why is it useful)

Answer 22

It increases the osmolarity of the medulla to allow passive water reabsorption more easily and means urine excretion requires less water

Question 23

Describe how urea recycling occurs

Answer 23

Urea is pumped into the filtrate via UT a2 transporter in the tin descending limb of the loop of Henle
Urea is pumped out into the medulla in the collecting duct via UT a3 and a1 transporters, increasing medulla osmolarity and encouraging passive water reabsorption
Urea is reabsorbed into the vasa recta via UT b1 transporter so it can be recylced and pumped into filtrate by UT a2 again

Question 24

What is the role of vasopressin in urea recycling?

Answer 24

It boosts numbers of UT a1 and a3

Question 25

What hormone boosts numbers of UT a1 and a3 ?

Answer 25

Vasopressin

Question 26

What is the main function of vasopressin?

Answer 26

Promote water reabsorption from collecting duct

Question 27

Where is vasopressin produced?

Answer 27

Hypothalamus (neurons in supraoptic & paraventricular nuclei)

Question 28

Where is vasopressin stored?

Answer 28

Posterior pituitary

Question 29

What factors that stimulate ADH production and release?

Answer 29

``` Increased plasma osmolarity Hypovolemia/low BP Nausea Angiotensin II Nicotine ```

Question 30

What factors that inhibit ADH production and release?

Answer 30

Reduced plasma osmolarity Hypervolemia/high BP Ethanol Atrial natriuretic peptide

Question 31

What detects fluctuations in plasma osmolarity?

Answer 31

Osmoreceptors

Question 32

Out of osmo and baroreceptors which is more sensitive?

Answer 32

Osmoreceptors

Question 33

How does ADH work?

Answer 33

It binds to the V2 receptor on the basolateral membrane of principal cells This causes a G protein cascade The cascade results in activation of protein kinase A This causes the no of aquaporin 2 channels to increase They insert into the apical membrane of principal cells This allows increased water reabsorbtion

Question 34

What is the name of the receptor for ADH and where is it found?

Answer 34

V2 receptor, found on the basolateral membrane of principal cells in the kidney

Question 35

What results in an increased no of aquaporin 2 channels?

Answer 35

Protein kinase A

Question 36

Where do aquaporin 2 channels insert?

Answer 36

Apical membrane of principal cells

Question 37

How is NaCl reabsorbed in the thick ascending limb?

Answer 37

Na+, K+ and 2 x Cl- move into the cell via symporter 3 Na+ are reabsorbed into blood while 2 K+ are pumped back into the cell by the Na+ K+ ATPase pump (this breaks one molecule of ATP into ADP+ Pi) The K+ Cl- symporter then pumps one molecule of each into the blood from in the cell

Question 38

What is the medical term for increased dilute urine excretion?

Answer 38

Diuresis

Question 39

How is NaCl reabsorbed in the DCT?

Answer 39

One Na+ and one Cl- are moved into the cell via symporter 3 Na+ are reabsorbed into blood while 2 K+ are pumped back into the cell by the Na+ K+ ATPase pump (this breaks one molecule of ATP into ADP+ Pi) The K+ Cl- symporter then pumps one molecule of each into the blood from in the cell

Question 40

How is Na+ reabsorbed in the principal cells of the collecting duct?

Answer 40

Na+ moves into the cell passively 3 Na+ are reabsorbed into blood while 2 K+ are pumped back into the cell by the Na+ K+ ATPase pump (this breaks one molecule of ATP into ADP+ Pi)

Question 41

What is the medical term for concentrated urine in low volume excretion?

Answer 41

Anti-diuresis

Question 42

What transporter is involved in Na+ reabsorption in the thick ascending limb?

Answer 42

Na+ - K+ - 2Cl- symporter

Question 43

What transporter is involved in Na+ reabsorption in the distal convoluted tubule?

Answer 43

Na+ - Cl- symporter

Question 44

What transporter is involved in Na+ reabsorption in the collecting duct?

Answer 44

Na+ channel

Question 45

What does ADH support the reabsorption of?

Answer 45

Na+

Question 46

What is ADH conc in anti diuresis?

Answer 46

High

Question 47

What is ADH conc in diuresis?

Answer 47

Low

Question 48

What is the cause of central diabetes insipidus?

Answer 48

Decreased or no production and release of ADH

Question 49

What are clinical features of central diabetes insipidus?

Answer 49

Polyuria | Polydipsia

Question 50

How is central diabetes insipidus treated?

Answer 50

External ADH

Question 51

What is the cause of syndrome of inappropriate ADH secretion (SIADH)?

Answer 51

Increased production and release of ADH

Question 52

What are clinical features of syndrome of inappropriate ADH secretion?

Answer 52

Hyperosmolar urine Hypervolemia Hyponatremia

Question 53

How is SIADH treated?

Answer 53

Non peptide inhibitor of ADH receptor

Question 54

What is the cause of nephrogenic diabetes insipidus?

Answer 54

Less or mutant aquaporin A2/V2 receptor

Question 55

What are clinical features of nephrogenic diabetes insipidus?

Answer 55

Polyuria | Polydipsia

Question 56

How is nephrogenic diabetes insipidus treated?

Answer 56

Thiazide diuretics and NSAIDs

Question 57

How is the acid base balance affected by our diet?

Answer 57

Acids and bases are added to our fluid compartment via our diet

Question 58

Are acids or bases excreted in the faeces?

Answer 58

Bases are

Question 59

After acid and base intake, what is the net addition in our body?

Answer 59

Acid 950-1000 mEq/day

Question 60

How are acids neutralised?

Answer 60

Bases react with the and form salts

Question 61

What is the role of kidneys in the acid base balance?

Answer 61

Secretion and excretion of H+ Reabsorption of hco3- Produce new hco3-

Question 62

What regulates the acid bases balance?

Answer 62

Kidneys and lungs

Question 63

When acids are neutralised what is formed?

Answer 63

Salt, water and co2

Question 64

What is the Henderson Hasselbalch equation used to calculate?

Answer 64

The pH of a buffer solution when you know the conc of acid and its conjugate base in the solution

Question 65

What type of acid base disorder is change in pco2 associated with?

Answer 65

Respiratory

Question 66

What type of acid base disorder is change in [hco3-] associated with?

Answer 66

Metabolic

Question 67

Where is most hco3- reabsorbed?

Answer 67

PCT (80%)

Question 68

What 2 types of cell in the DCT are associated with hco3-?

Answer 68

Alpha and beta intercalated cells

Question 69

What happens to hco3- and h+ in alpha intercalated cells?

Answer 69

hco3- is reabsorbed | h+ is secreted

Question 70

What happens to hco3- and h+ in beta intercalated cells?

Answer 70

hco3- is secreted | h+ is reabsorbed

Question 71

Out of alpha and beta intercalated cells which is usually more important?

Answer 71

Alpha

Question 72

How is hco3- produced in the PCT?

Answer 72

Glutamine is broken down into 2 ammonia molecules and 2 hco3-

Question 73

What is required alongside bicarbonate ion reabsorption to neutralise the acid?

Answer 73

New bicarbonate ion production

Question 74

In the nephron, what area has the highest osmolarity?

Answer 74

The tip of the loop of Henle as it is the first part of the nephron in the medulla and has the highest osmolarity threshold (1200 mOsm/L)

Question 75

Why would chronic cirrhosis lead to high urine osmolarity?

Answer 75

Chronic cirrhosis causes urine retention in the body, the blood vessels therefore dilate and baroreceptors sense low BP. They will therefore release ADH increasing water reabsorption and increasing urine osmolarity

Question 76

What compartment does water first go into when we drink it?

Answer 76

Extracellular

Question 77

Which component of urine has no effect on ADH production?

Answer 77

Urea

Question 78

What effect does ethanol have on ADH levels?

Answer 78

Inhibits ADH release