1: Physiology 4 & 5 Flashcards Preview

Renal Week 2 2017/18 > 1: Physiology 4 & 5 > Flashcards

Flashcards in 1: Physiology 4 & 5 Deck (58)
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1

Where does the majority of reabsorption occur?

Proximal tubule

2

What is a normal healthy GFR?

125 ml/min

3

Why is reabsorption specific?

Specific transport proteins

4

What is the osmolarity of the fluid at the start of the proximal tubules compared to that at the end?

The same

no change in osmolarity

5

Which process mainly occurs in the proximal tubule?

Reabsorption

6

Does secretion occur in the proximal tubule?

Some secretion

7

By which two means can substances be reabsorbed into peritubular capillaries?

Transcellular (through cell membranes)

Paracellular (through tight junctions)

8

What is primary active transport?

Energy used to transport a substance against its concentration gradient using a carrier

9

What is secondary active transport?

Active transport of a substance by carriers COUPLED to the concentration gradient of another ion

10

Secondary active transport usually occurs using the concentration gradient of which ion?

Sodium

11

What is facilitated diffusion?

Passive transport WITH A CARRIER

12

Where is 2/3rds of filtered sodium reabsorbed?

Proximal tubules

13

Where are NaKATPases found on the tubular cells of the proximal tubules?

Basolateral

empties into capillaries

14

What is the function of NaKATPases on the basolateral membrane of the tubular cells?

What does this achieve?

Active transport of 3 Na OUT and 2 K IN

Maintains concentration gradient of sodium

So it can diffuse in (be reabsorbed) at the apical membrane

15

Where do sodium ions go once they have been secreted OUT of tubular cells by NaKATPase?

Peritubular capillaries

leaving conc gradient from filtrate to tubular cells

16

The transport of sodium from the filtrate to the capillaries sets up which types of gradient?

CONCENTRATION GRADIENT FOR SODIUM (so more is reabsorbed from proximal tubules)

OSMOTIC GRADIENT FOR WATER (following sodium)

ELECTROCHEMICAL GRADIENT FOR CHLORINE (so it's reabsorbed by the PARACELLULAR route)

 

17

By which routes are sodium and chlorine reabsorbed?

Sodium - transcellular

Chlorine - paracellular

18

Why doesn't the osmolarity of the proximal tubules decrease as you go along?

Water and salt reabsorbed equally

19

By which means does glucose leave proximal tubules?

Co-transport with sodium (SGLT2)

20

How does glucose leave the tubular cells by the basolateral membrane?

FACILITATED DIFFUSION down its concentration gradient

GLUT2?

21

How does water follow sodium and glucose into the peritubular capillaries?

Paracellular reabsorption

22

Which two substances are reabsorbed via the paracellular route?

Water

Chloride ions

23

What proportion of glucose is reabsorbed in the proximal tubules?

100% normally

24

What is the equation for rate of filtration?

Rate of filtration = [substance]plasma x GFR

25

Does the rate of reabsorption of glucose increase in proportion with its rate of filtration?

Yes, up to the point where all the carriers are saturated

26

Which transporter is saturated when the rate of filtration of glucose is too high?

SGLT2

co-transporter

27

Which rate starts to increase if you pass the maximum rate of reabsorption of glucose?

Rate of excretion

glycosuria

28

What is the TM of glucose?

Transport maximum of glucose

RATE OF FILTRATION AFTER WHICH YOU START TO EXCRETE GLUCOSE

2 mmol/min

29

What is the

a) rate of filtration

b) plasma concentration

of glucose after which you start to get glycosuria?

a) 2 mmol/min, transport maximum

b) Around 12 mmol/L

30

After you reach the transport maximum for glucose, glucose is excreted by the kidneys, producing which sign?

Glycosuria