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Flashcards in Handling Sodium And Hypertension Deck (86)
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1

What is the most osmotically effective solute in the ECF?

Na+

2

The input and output of Na+ is approximately how much per day?

10.5 g/day

3

How is Na+ lost from the body?

Urine (10g)
Sweat (0.25g)
Faeces (0.25g)

4

What is the osmotic status of sweat?

Hypo-osmotic

5

In which part of the nephron can we control how much Na+ is reabsorbed?

DCT

6

What percentage of sodium is reabsorbed in the PCT?

67%

7

How will changes in the peritubular capillaries affect the PCT Na+ reabsorption?

Decreased pressure in capillaries = increased reabsorption
Increased pressure in capillaries = decreased reabsorption

8

Describe what happens to Na+ reabsorption when renal BP increases

Decreased Na-H antiporter and reduced ATPase activity
Decreased Na+ reabsorption in PCT
Decreased water reabsorption in PCT
ECF volume decreases
BP decreases

9

How is Cl- reabsorbed?

Transcellular (active)
Paracellular (passive)
Coupled to pumps and dependent of Na+

10

What percentage of bicarbonate is reabsorbed in the PCT?

90%

11

What percentage of Cl- is reabsorbed in the PCT?

60%

12

Which sodium transporters are present in the PCT?

Na-H antiporter
Na-glucose symporter
Na-AA cotransporter
Na-Pi

13

Which sodium transporter is present in the loop of Henle?

NaKCC symporter

14

Which sodium transporter is present in the early DCT?

NaCl symporter

15

Which sodium transporter is present in the late DCT and CD?

ENaC

16

Which molecules are reabsorbed up to 100% in the PCT?

Glucose
Amino acids
Lactate

17

What is the order of molecules reabsorbed as you travel down the PCT?

First = glucose, amino acids, lactate
Second = bicarbonate
Third = phosphate
Fourth = chloride

18

How is the PCT divided?

3 segments
S1, S2, S3

19

Describe the glomerulotubular balance

Autoregulation - blunts Na+ excretion in response to GFR changes
Always try to take 67% of whatever is filtered
Higher GFR -> more reabsorption

20

How come the PCT can regulate how much Na+ it reabsorbs?

Because the PCT has flexibility due to not using all of its transporters all of the time

21

What is the equation for filtered load?

Filtered load = GFR x concentration

22

What is the osmotic status of the filtrate at the bottom of the loop?

Hypertonic in comparison to plasma

23

How does Na+ reabsorption occur in the thin ascending limb?

Relies on the steep gradient of Na+ conc to drive passive reabsorption of Na+

24

How does Na+ reabsorption occur in the thick ascending limb?

Active (pumped)

25

What does NKCC2 move?

Na+, K+ and 2Cl- from filtrate into cells

26

What happens to the ions that pass through NKCC2?

Na+ pumped into interstitium via ATPase
K+ diffuses via ROMK back into the tubule
Cl- diffuses into the interstitium

27

Which region of the nephron is particularly sensitive to hypoxia?

Thick ascending limb of loop of Henle
Uses the most energy

28

What is the osmotic status of filtrate leaving the loop of Henle?

Hypo-osmotic in comparison to plasma

29

Why is the filtrate further diluted in the DCT?

Because active Na+ reabsorption can occur but the water permeability of the DCT is fairly low so water cannot follow

30

In the late DCt and CD, what does water permeability depend on?

ADH