Kidney function III

Question 1

what is oliguria

Answer 1

Low vol of urine produced - below 0.428L/day

Question 2

What is osmolar clearance

Answer 2

volume of plasma cleared of osmotically active particles per unit time

Question 3

How do you calculate osmolar clearance

Answer 3

C = UV/P where U = osmolarity of urine mosm/ml
V = urine flow rate ml/min
P = plasma osmolarity mosm/ml
C = osmolar clearance ml/min

Question 4

What is typical fasting osmolar clearance

Answer 4

2-3 ml/min

Question 5

How do you calculate free water clearance

Answer 5

Renal clearance - osmolar clearance = free water clearance

Question 6

What is the free water clearance of a patient producing hypotonic urine

Answer 6

> 0

Question 7

What is the free water clearance of a patient producing hypertonic urine

Answer 7

<0

Question 8

What is the free water clearance of a patient producing isotonic urine

Answer 8

0

Question 9

Where are the osmoreceptors that are involved in the release of ADH

Answer 9

Organum vasculosum lamina terminalis
Medican preoptic nucleus
subformical organ

Question 10

What do the osmoreceptors involved in the release of ADH signal to?

Answer 10

Magnocellular neurosecretory cells in paraventricular supraoptic nuclei in hypothalamus

Question 11

Why is ADH effective in its role

Answer 11

It has a short life span = 20-30 mins allowing for fine control

It is released rapidly

Question 12

What effect does angiotensin II have on ADH secretion

Answer 12

It increases it

Question 13

What effect does natriuretic peptides have on ADH secretion

Answer 13

It decreases it

Question 14

What effect does nicotine have on ADH

Answer 14

+

Question 15

What effect does nausea have on ADH

Answer 15

+

Question 16

What effect does pain have on ADH

Answer 16

+

Question 17

What effect does stress have on ADH

Answer 17

+

Question 18

What effect does alcohol have on ADH

Answer 18

-

Question 19

What can promote/inhibit ADH other than osmoreceptor action?

Answer 19

Alcohol
Stress
Nausea
Pain
Nicotine

Question 20

What are the two types of diabetes insipidus

Answer 20

Neurogenic; congenital or from brain injury, trauma, tumour

Nephrogenic; inherited (mutated V2, AQP2 gene), acquired from infection, drug

Question 21

What mutations can cause nephrogenic diabetes insipidus

Answer 21

Mutated V2 or AQP2 gene

Question 22

What are the characteristics of diabetes polyuria

Answer 22

Polyuria
Polydipsia
nocturia

Question 23

Describe the physiology of the reabsorption of K+ in the PCT of the nephron

Answer 23

There is a K+ ion in the apical membrane which is used to move K+ from inside the cell into the lumen.
Then there is transcellular movt of K+ from lumen into the interstitial space.
The Na+:K+ ATPase in the basolateral membrane moves K+ into the cell and then another K+ channel allows K+ to flow into interstitial fluid from inside the cell.
Then a K+:CL- co-transporter also pumps K+ into interstitial fluid
There is paracellular movt of K+ too

Question 24

Describe the physiology of the reabsorption of K+ in the thick ascending limb of the LOH of the nephron

Answer 24

In the apical membrane there is a Na+:K+:Cl- cotransporter moving ions inside the cell (NKCC2 transporter). There is also a K+ channel moving K+ ions back into the lumen.
There is a Na:K ATPase pump moving K+ in to the cell. There is a K+ channel in the basolateral membrane moving K+ from the cell into the interstitial space.
There is a K+:CL- cotransporter moving K+ out of the cell with Cl-
There is paracellular movt of K+

Question 25

Describe the physiology of the reabsorption K+ in the collecting ducts

Answer 25

Occurs in the intercalated cells of the collecting duct. There is a H+:K+ exchanger that moves K+ into the cells in favour of H+ from the lumen of the nephron. Then there is a K+ channel in the basolateral membrane which removes K+ from the cell and allows it to travel into the interstitial space.

Question 26

Describe the physiology of the secretion of K+ in the collecting ducts

Answer 26

Occurs in the principle cells of the collecting duct. There is a Na:K ATPase pump in the basolateral membrane that moves K+ into the cells. K+ channels in the apical membrane called ROMK = renal outer medullary K+ channels; and Ca2+ activated big conductance K+ channels that allow the flow of K from within the cell into the lumen of the nephron. There is a Na channel in the apical membrane that allows Na to enter the cell from the lumen. There is also a K:Cl cotransporter in the apical membrane which removes ions from the cell and places them in the lumen. There is a K+ channel in the basolateral membrane which moves ions from inside the cell out.

Question 27

What are the K+ channels found in the apical membrane of the principle cells of the collecting ducts of the nephron.

Answer 27

Renal outer medullary K+ channels (ROMK) | Ca2+ activated big conductance K+ channels

Question 28

What effect does aldosterone have on K+ channels in the nephron?

Answer 28

It activates them

Question 29

What effect does tubular flow rate have on K+ secretion and why?

Answer 29

It increases it as positive charges are washed away when tubular flow is higher meaning that an electrochemical gradient is maintained.

Question 30

What effect does acidosis have on K+ secretion?

Answer 30

It inhibits it

Question 31

What effect does alkalosis have on K+ secretion?

Answer 31

It stimulates it

Question 32

What is hypokalaemia?

Answer 32

Plasma [K+] < 3.5 mM

Question 33

What causes hypokalaemia?

Answer 33

Increased tubular flow rate (increased K+ secretion) Hyperaldosteronism Alkalosis

Question 34

How would you treat a patient with hypokalaemia?

Answer 34

KCl administered via IV or orally Feed w/ foods rich in K+ Treat alkalosis

Question 35

What is hyperkalaemia?

Answer 35

Plasma [K+] > 5.5mM

Question 36

How would you treat a patient with hyperkalaemia?

Answer 36

Short term -> give Ca2+ to antagonise effect of K+ on heart muscle Intermediate term -> Give insulin to move K+ into cells, give glucose to prevent hypoglycaemia Long term -> remove K+ from body giving diuretics

Question 37

Possible C(H2O) range

Answer 37

-1.3 to 14.5 ml/min

Question 38

How do osmoreceptors work

Answer 38

The OVLT, MPN and SFO signal to magnocellular neurosecretory cells in the paraventricular and supraoptic nuclei in the hypothalamus which then causes the release of ADH from the posterior pituitary gland

Question 39

Normal range of plasma osmolality

Answer 39

285-295 mosm/kg

Question 40

What are the characteristics of diabetes insipidus

Answer 40

nocturia polyuria polydipsia

Question 41

Describe osmotic diuresis

Answer 41

``` Increased blood glucose more glomerular filtration of glucose, increased osmolarity of filtrate decreased water reabsorption polyuria ```

Question 42

Where is the largest amount of potassium reabsorbed in the kidney

Answer 42

%65 absorbed passively in the proximal tubule

Question 43

What type of co transporter is used to absorbed K in the asc LOH

Answer 43

NKCC2

Question 44

What type of exchanger is used to absorbed K in the distal tubule

Answer 44

K+:H+ exchanger

Question 45

What is the normal K plasma range

Answer 45

3.5-5 mM