12. Renal Physiology

Question 1

The following are involved in renal autoregulation:

Select true or false for each of the following statements.

A.	Adenosine				
B.	Aldosterone			
C.	Bradykinin		
D.	Prostaglandin E2		
E.	Vasopressin

Answer 1

A. True. Adenosine is an inhibitory influence in renal autoregulation, being produced when hydration/perfusion are good to limit renal blood flow/glomerular filtration

B. False. Aldosterone, bradykinin and vasopressin are not involved in renal autoregulation

C. False. See Feedback B

D. True. PEGE2 dilates the afferent arteriole to maintain renal blood flow when perfusion pressure falls

E. False. See Feedback B

only ADENOSIDE AND PGE2

Question 2

Adenosine effect on renal auto regulation?

Answer 2

Adenosine is an inhibitory influence in renal autoregulation, being produced when hydration/perfusion are good to limit renal blood flow/glomerular filtration

Question 3

PGE2 effect on renal auto regulation?

Answer 3

PGE2 dilates the afferent arteriole to maintain renal blood flow when perfusion pressure falls

Question 4

What do you need to measure GFR?

Answer 4

Clearance of marker

RBF or filtration fraction not needed

Question 5

How is chloride re-absorbed renally?

Answer 5

Chloride is reabsorbed in the PCT passively down its concentration gradient via the para-cellular route.

Question 6

How is bicarbonate transported in the kidney?

Answer 6

Actively reabsorbed as CO2

Question 7

How much glucose is reabsorbed a day?

Answer 7

160 g = 900 mmol

Question 8

What influence has the autonomic system on the kidneys?

Answer 8

Sympathetic innervation (B1 receptors) of the JGA contributes to renin release

Question 9

Where in the nephron does ADH act, which receptor and what does it do?

Answer 9

Promotes H2O reabsorption in the COLLECTING DUCT, cell surface receptor GPC.

Question 10

What is the main objective of the counter current multiplier system?

Answer 10

to generate a hyperosmolar environment in the renal medulla

Question 11

What is the main energy consuming activity of the nephron?

Answer 11

Sodium reabsorption, at the Na/K ATPase pump.

Question 12

Whats the main method for glucose reabsorption?

Answer 12

The Na+/glucose symporter is the main method for glucose reabsorption.

Question 13

Where in the nephron does H+ extrusion occur?

Answer 13

Na+ reabsorption/H+ extrusion occurs in the

PROXIMAL TUBULE

Question 14

In the Proximal tubule:
1. What percentage of the filtered potassium and water is reabsorbed?

2. How much water over all is reabsorbed by the nephron.

Answer 14

in the PT - 2/3 water and potassium filtered is reabsorbed

in the nephron - 99% water reabsorbed.

Question 15

Is the ascending limb of the loop of henle permeable to water?

Answer 15

Ascending limb is impermeable to water.

Question 16

An increase in GFR increases the risk of glycosuria: T/F

Answer 16

True.

Glucose delivery to the PCT is determined by the concentration and the GFR. At a concentration of 8 mmol/L and a GFR of 125 mL/min, the delivery rate of glucose is 1 mmol/minute.

Question 17

What is the tubular transport maximum for glucose?

Answer 17

Tmax for glucose is between 1.5-2.0 mmol/minute

Question 18

Which of the following have a higher intracellular than extracellular concentration:

Phosphate, 
Magnesium,
Potassium,
Calcium,
Bicarbonate

Answer 18

Phosphate,
Magnesium,
Potassium

Question 19

ADH determines whether the majority of water is reabsorbed by the nephron or excreted? T/F

Answer 19

False,

majority of water is reabsorbed at the PCT regardless of ADH.

Question 20

During renal auto regulation:

1. is there contribution directly from sympathetic nervous system?
2. Does it involve simultaneous constriction of afferent and efferent arteriole?

Answer 20

1. No, only from angiotensin 2

2. No, contributions come from afferent dilatation and efferent constriction.

Question 21

During renal auto regulation:

Maintains a constant renal artery pressure despite changes in blood flow? T/F

Answer 21

False,

constant flow is maintained despite pressure.

Question 22

Renal autoregulation:

Increases glomerular filtration fraction in the presence of hypovolaemia. T/F

Answer 22

TRUE

An increase in filtration fraction maintains GFR

Question 23

Which side of the cell is the main active process of sodium transport occuring?

Answer 23

The main active process is the Na+/K+ pump on the BASAL side of the cell.

Question 24

How much salt is reabsorbed per day by the kidney?

Answer 24

1. 5 kg

99. 5% of it

Question 25

What is NKCC?

Answer 25

It is the Na-K-Cl cotransporter in the ascending limb, loop of henle that reabsorbs potassium and chloride.

Question 26

What is the site of action of aldosterone?

Answer 26

Principal cell, DCT

This decides the final sodium excretion.

Question 27

Whats the normal filtration fraction?

Answer 27

15-20%

Question 28

In fluid entering the LOH, Fluid is isotonic with plasma?

Answer 28

True - 300 mOsmol/L

Question 29

Which limb of LOH does Na reabsorption occur?

Answer 29

Thick ascending limb

Question 30

What percentage of loops in LOH pass deeply into the medulla?

Answer 30

15%

Question 31

Half life of angiotensin II?

Answer 31

less than 30 seconds.

Question 32

How is plasma osmolarity affected differently by ADH and aldosterone?

Answer 32

ADH - reduces plasma osmolarity - just H2O reabsorption. Increases urine osmolarity.

Aldosterone - reabsorbs H2O via reabsorbing Na and excreting K, on balance has less determination of osmolarity of plasma or urine.

That is decided by ADH.