Reabsorption And Secretion 1, 2

Front 1

Movement of solutes from blood thru glomerulus into tubules is called _____________

Back 1

filtration

Front 2

Movement of solutes from tubules into peritubular capillaries is called ____________

Back 2

reabsorption

Front 3

Movement of solutes from peritubular capillary blood into tubular fluid is called____________

Back 3

secretion

Front 4

Calculation of filtered load:

Back 4

Filtered load = GFR * [P]x = GFR * Concentraiton of X in plasma.

GFR is clearance of inulin, NOT X

Front 5

Calculation of excretion rate:

Back 5

Excretion rate = (Urine flow rate)*(Concentration of substance X in urine) = V*[U]x

Front 6

Reabsorption or secretion rate =

Back 6

Filtered load - Excretion rate

Front 7

If filtered load > excretion rate, what does that mean?

Back 7

Net reabsorption

Front 8

If filtered load < excretion, what does that mean?

Back 8

Net secretion

Front 9

What extra step to take for substances bound to plasma proteins?

Back 9

Since if they're bound to proteins they're not freely filtered, you have to modify the filtered load calculation by the % free (unbound). eg., if substance if 30% bound, multiply by .7 (because it's 70% free)

Front 10

Where does glucose get reabsorbed?

Back 10

Early proximal tubule

Front 11

What is threshold in relation to glucose?

Back 11

The [glucose] at which it begins to appear in urine

Front 12

What type of transporter carries glucose out of tubule?

Back 12

Na+/glucose cotransporter that gets energy from Na+ gradient

Front 13

What is splay?

Back 13

The phenomenon whereby glucose appears in the urine before transporters are saturated

Front 14

What is Tm analogous to?

Back 14

Vmax.

Front 15

Where does secretion of PAH occur?

Back 15

In proximal tubule

Front 16

What happens once PAH carriers become saturated?

Back 16

Excretion increases less steeply (but still increases)

Front 17

In order to measure RPF with PAH clearance, would you choose a plasma [PAH] above or below Tm?

Back 17

Below. Above it you wouldn't be picking up ALL the PAH and RPF would be underestimated.

Front 18

Is urea filtered, reabsorbed, or secreted?

Back 18

It is filtered, reabsorbed, AND secreted

Front 19

What percentage of filtered urea is excreted in urine?

Back 19

About 40%. There is net reabsorption.

Front 20

Where is urea reabsorbed?

Back 20

1) 50% is reabsorbed immediately in <b>proximal convoluted tubule</b>. Concentration gradient is because as water is quickly reabsorbed, urea is left behind, creating a gradient.

2) 110% is secreted in <b>thin limb</b>. This is because there is a very high urea concentration here, so it goes back into the nephron tubule.

3)When we get to <b>inner medullary collecting ducts </b>, where urea is very high, UT1 (a facilitated diffusion transporter exists. Urea is reabsorbed by UT1. If ADH is present, about 40% of urea in the ultrafiltrate makes it into the urine.

Front 21

As urine flow increases, urea excretion (increases, decreases).

Back 21

Increases.

This is due to concentration difference. Low urine flow means most water is getting reabsorbed, so urea concentration is high. High urea concentration drives greater reabsorption. High urine flow means most water isn't getting reabsorbed, so urea concentration in the water is low.

Front 22

Regardless of whether reabsorption or secretion, Urea always moves down its concentration gradient. T/F

Back 22

True

Front 23

Where is the nephron impermeable to urea?

Back 23

Thick ascending limb, distal tubule, cortical and outer medullary collecting ducts.

Front 24

What turns on UT1?

Back 24

ADH

Front 25

What is urea recycling?

Back 25

Urea gets reabsorbed only in the presence of ADH. Without ADH, urea that would otherwise have been excreted is recycled.

Front 26

At high pH, what forms of weak acid and base predominate?

Back 26

Under alkaline conditions, A- and B predominate

Front 27

At low pH, what forms of weake acid and base predominate?

Back 27

Under acidic conditions, HA and BH+ predominate

Front 28

If you want to get rid of an overdose of weak base, what do you do to urine?

Back 28

You want it to be in the BH+ form so it can't be reabsorbed once secreted. (Only the B form can be reabsorbed)

Front 29

In what form is the kidney permeable to weak acids and bases?

Back 29

UNCHARGED form (non-ionic)

Front 30

If you want to get rid of an overdose of weak acid, what do you do to urine?

Back 30

You want it to be in the A- form, so it can't get reabsorbed once it's in the tubule. Alkalinize the urine to put it into the A- form.