Renal Control of Sodium Ions

Question 1

Explain how changes in concentration of sodium affect blood pressure.

Answer 1

• Increase in concentration of sodium in the lumen of blood vessels results in a greater osmotic pressure
• Water moves to an area of higher osmotic pressure and therefore greater amount of water moves into the lumen of blood vessels
• This results in an increased extra cellular fluid

Question 2

Which part of the nephron has the most variation in how much sodium is reabsorbed?

Answer 2

DCT

Question 3

Which section of the nephron is a common target site of diuretics and why?

Answer 3

• DCT

- It is the most variation in how much sodium is reabsorbed

Question 4

How does aldosterone increase reabsorption of sodium?

Answer 4

Increases production of eNac so more sodium is reabsorbed via the channel.

Question 5

Define pressure natriuresis.

Answer 5

A central component of the feedback system for long-term control of arterial pressure is the pressure-natriuresis mechanism, whereby increases in renal perfusion pressure lead to decreases in sodium reabsorption and increases in sodium excretion

Question 6

Define pressure diuresis.

Answer 6

Increased urinary excretion of water when there is an increase of arterial pressure, a compensatory mechanism to maintain blood pressure within the normal range.

Question 7

TRUE OR FALSE:

Pressure natriuresis and diuresis always occur together.

Answer 7

True, because water follows sodium.

Question 8

What ions does the Na-H antiporter (NHE) protein transporter move?

Answer 8

1 Na+ in, 1 H+ out

Question 9

What ions does the Na-Glucose symporter (SGLUT) protein transporter move?

Answer 9

1 Na+ in, 1 Glucose in

Question 10

What ions does the NaKCC2 protein transporter move?

Answer 10

1 Na+ in, 1 K+ in, 2 Cl- in

Question 11

What ions does the NaCl co-transporter protein transporter move?

Answer 11

1 Na+ in, 1 Cl-

Question 12

What ions does the ENaC protein transporter move?

Answer 12

1 Na+ in

Question 13

What apical transporters are present on the PCT?

Answer 13

The PCT is split into 3 different segments which use different apical transporters for transcellular reabsorption.

These channels are required as the first segment is concerned with reabsorbing glucose, amino acids, HCO3- and Pi.

These channels are required as the second and third segment is concerned with reabsorbing chlorine and water.

Question 14

How do the levels of PTH impact the NaPi channels present in the first segment of the PCT?

Answer 14

PTH also inhibits phosphate reabsorption in the kidney therefore decreases the presence of these channels.

Question 15

Describe the function of the descending limb of the loop of Henle.

Answer 15

Site of water reaborption due to increased sodium in the interstitial fluid. Therefore water is passively reabsorbed forming an hypertonic environment within the tubule.

Question 16

What is the tonicity of the tubule lumen like at the bottom of the loop of Henle?

Answer 16

Hypertonic

Question 17

What is the tonicity of the tubule lumen like at the end of the thick ascending limb?

Answer 17

hypotonic

Question 18

Describe the function of the thin ascending limb of the loop of Henle.

Answer 18

Basically the opposite of the descending limb. Here sodium is passively reabsorbed due to the low osmolality of the surrounding interstitial fluid.

Question 19

Describe the function of the thick ascending limb of the loop of Henle.

Answer 19

This area of the loop of Henle is impermeable to water.

Here reabsorption of sodium becomes a more active process due to a lesser concentration gradient and also greater activity of 3Na-2K-ATPase. Therefore, the contents of the tubular lumen becomes increasingly hypotonic.

Question 20

Name the main channel proteins present in the thick ascending limb.

Answer 20

3Na-2K-ATPase is present on the basolateral membrane in order to drive the movement of the apical channels which include, NKCC2, ROMK.

Question 21

What ions does the ROMK protein transporter move?

Answer 21

One K+ out

Question 22

What do loop diuretics inhibit?

Answer 22

Channel protein NKCC2

Question 23

What do thiazide diuretics inhibit?

Answer 23

NaCl co-transporter channel protein

Question 24

What do potassium sparing diuretics inhibit?

Answer 24

Channel protein ENaC

Question 25

Describe the difference in channel proteins in the early and the late convoluted.

Answer 25

DCT 1: 3Na-2K-ATPase is present on the basolateral membrane in order to drive the movement of the apical channels which include, NaCl co-transporter.

DCT 2: 3Na-2K-ATPase is present on the basolateral membrane in order to drive the movement of the apical channels which include, NaCl co-transporter and ENaC.

Question 26

What is the tonicity of the tubule lumen like at the end of the DCT and why?

Answer 26

Extremely hypotonic as the tubule is impermeable to water.

Question 27

How is chloride reabsorbed in the DCT?

Answer 27

Both through NaCl co-transporter and paracellularly due to the electrochemical gradient formed by the movement of sodium ions through ENaC.

Question 28

Which adrenal hormone increases the presence of ENaC within the DCT?

Answer 28

Aldosterone

Question 29

Where is the major site of calcium reabsorbtion in the nephron?

Answer 29

DCT

Question 30

What 2 hormones as the main regulators of Ca2+ reabsorbtion in the kidneys?

Answer 30

1. PTH

2. 1,25-dihydroxyvitamin D (Calcitriol)

Question 31

What 3 types of cells exist within the collecting duct of a nephron?

Answer 31

1. Principal
2. Acid intercalated (A-IC)
3. Base intercalated (B-IC)

Question 32

Describe the function of principal cells.

Answer 32

They reabsorb sodium through ENaC, this creates an electrochemical gradient which drives paracelluar reabsorption of chloride ions.

Also they are permeable to water so water reabsorption also occurs. (Depending on availability of aquaporrins)

Question 33

Describe the function of intercalated cells.

Answer 33

To maintain acid base balance through excretion of H= ions and reabsorption of HCO3-.