Topic 8 B What happens in each segment

Question 1

Proximal Tubule % of filtered load of sodium & water reabsorbed

Answer 1

65%

Little less % for chloride
Quantity can be increased or decreased as needed

Question 2

Proximal Tubule - mitochondria amount? why?

Answer 2

Contain large number of mitochondria
to support extensive active transport
activity

Question 3

Proximal Tubule Ultrastructure Luminal border contains what?

Answer 3

extensive number of protein carrier molecules

Question 4

Proximal Tubule Ultrastructure Co-transport of what?

Answer 4

amino acids and glucose

Question 5

Proximal Tubule Ultrastructure Counter transport of what?

Answer 5

hydrogen ions (move a large quantity of hydrogen ions against small hydrogen ion gradient

Question 6

Proximal Tubule Ultrastructure Basolateral border contains extensive amounts of what?

Answer 6

extensive amount of N-K ATPase

Question 7

First half of Proximal tubule- co-transport of what ? what does it do to Na levels?

Answer 7

Extensive co-transport of sodium with glucose and amino acids
Sodium reabsorption carries glucose, bicarb, organic ions leaving chloride resulting in increasing [Cl-]

105 mEq/L increases to 140 mEq/L

Question 8

Second half of Proximal Tubule –

Cl concentration ?

Answer 8

High chloride concentration favors chloride diffusion

Some movement may occur through specific chloride channels

Question 9

Second half of Proximal Tubule –

Electrochemical gradient created by reabsorption how??

Answer 9

Most glucose & amino acids have been reabsorbed–sodium reabsorption drives chloride reabsorption
Electrochemical gradient

Question 10

Many end products of metabolism are secreted by proximal tubule (4)

Answer 10

Bile salts
Oxalate
Urate
Various catecholamines

Question 11

drugs & toxins secreted in proximal tubule (2)

Answer 11

Penicillin

Salicylates

Question 12

Para-aminohippuric acid secreted in proximal tubule – what % used to determine what?

Answer 12

90% of PAH in renal blood flow is removed

Can be used to determine renal blood flow

Question 13

Thin descending and ascending LOH segments characteristics ? (4)

Answer 13

Thin epithelial membrane
No brush border
Few mitochondria
Minimal metabolic level

Question 14

Thin descending segment of LOH - permeability to H2O and solutes?

Answer 14

Highly permeable to water

Moderately permeable to most solute

Question 15

Thin descending segment of LOH - diffusion?

Answer 15

Allows diffusion of water and solutes

Question 16

Thin descending segment of LOH - reabsorption %?

Answer 16

No active reabsorption

20% of water reabsorption occurs in the loop of Henle

Question 17

Thin ascending segment - H2O permeability?

Answer 17

impermeable to water

Part of mechanism for concentrating urine

Question 18

Thick Ascending LOH - epithelial cells characteristics?

Answer 18

Thick epithelial cells with high concentration of mitochondria

Question 19

Thick Ascending LOH - what % of sodium, chloride, & potassium reabsorbed is filtered load?

Answer 19

(Approx 25% of filtered load)

Question 20

Thick Ascending LOH - water permeability ?

Fluid is what?

Answer 20

Impermeable to water

As solute reabsorb luminal solute concentrations drop especially since water NOT reabsorbed–Fluid very dilute

Question 21

Sodium Reabsorption is driven by what in basolateral border of tubule cells?

Answer 21

N-K ATPase

Question 22

Two transport mechanisms move sodium from tubular lumen (in LOH)

Answer 22

• 1 Na-2Cl-1K co-transport mechanism

- Na-H counter-transport mechanism

Question 23

Primary transport means of moving sodium out of lumen into tubular cells (in LOH)

Answer 23

1 Na-2Cl-1K co-transport mechanism
Potassium reabsorbed AGAINST potassium concentration gradient
Cl-& K+ diffuse out of cell into renal interstitial fluid via specific ion channels

Question 24

What loop diuretics inhibit the action of the 1Na-2Cl-1K co-transport mechanism out of lumen into tubular cells (in the LOH)

Answer 24

furosemide, ethacrynic acid, bumetanide

Question 25

LOOP Diuretics - cause less sodium reabsorption does what to H2O and K

Answer 25

Less sodium reabsorption–less H2O reabsorption in later segments of the nephron Less sodium reabsorption–less K reabsorption with potential loss of K

Question 26

Na-Cl-K co-transport mechanism is what? | in LOH lumen

Answer 26

is isoelectric | BUT K able to diffuse back into lumen via potassium channels creating +8 mV positive charge in tubule lumen

Question 27

Electrical gradient in LOH lumen and tubular cells drives diffusion of what?

Answer 27

Electrical gradient drives diffusion of Na+, K+, Mg++ & Ca++ into the renal interstitial space via the tight junctions (paracellular diffusion)

Question 28

Macula densa is where??

Answer 28

first part of distal tubule | Part of juxtaglomerular complex

Question 29

Macula densa provides what?

Answer 29

Provides feedback control for GFR and blood flow (for this nephron)

Question 30

What is the segment after the macula densa in the distal tubule ? and reabsorption?

Answer 30

High convoluted Segment | Solute reabsorption–no water reabsorption

Question 31

The High Convoluted Segment is also known as what segment of the distal tubule?

Answer 31

Diluting segment of distal tubule

Question 32

In Early Distal Tubule what % of filtered load for sodium & chloride reabsorbed

Answer 32

5%

Question 33

In Early Distal Tubule reabsorbed is driven by what?

Answer 33

Driven by Na-K ATPase in basolateral border of tubular cells

Question 34

In Early Distal Tubule Na-Cl co-transport mechanism moves Na and Cl where?

Answer 34

mechanism moves Na+ and Cl-into cell down [Na+] | Chloride diffuses out of cell via chloride specific channels

Question 35

Thiazide diuretics inhibit what mechanism? (in the early distal tubule)

Answer 35

Na-Cl co-transport mechanism | Reduces sodium and chloride reabsorption and ultimately water reabsorption in later segments of nephron

Question 36

Late Distal Tubule & Cortical Collecting Tubule | Membranes permeability to urea?

Answer 36

impermeable to urea All urea entering exits to collecting duct to be excreted Some reabsorption of urea will occur in medullary collecting ducts

Question 37

Late Distal Tubule & Cortical Collecting Tubule | Na and K secretion is controlled by what?

Answer 37

secretion controlled by various hormones but especially by aldosterone

Question 38

Late Distal Tubule & Cortical Collecting Tubule | H+ ions secretion?

Answer 38

Able to secrete hydrogen ions against large concentration gradient (1000:1) Proximal tubule moves hydrogen ions against small gradient (4 to 10:1)

Question 39

Water permeability controlled by concentration of what?

Answer 39

antidiuretic hormone (ADH, aka vasopressin) No ADH-no water permeability–excrete dilute urine Increased conc of ADH increase permeability of water & decrease the volume of urine and increase the conc of the urine

Question 40

Two types of cells in late distal and cortical collecting duct

Answer 40

Principal cells | Intercalated cells

Question 41

Principal cells in late distal and cortical collecting duct do what?

Answer 41

Reabsorb sodium & water | Secrete potassium

Question 42

Intercalated cells in late distal and cortical collecting ducts do what?

Answer 42

Reabsorb potassium | Secrete hydrogen

Question 43

Principal Cells - what pump drives activity? what border is it on? which way does everything go?

Answer 43

Na-K ATPase in basolateral borders of tubule cells drives activity Na follows concentration gradient–diffuses through sodium specific channels K follows concentration gradient out of cell into tubular lumen via potassium specific channels

Question 44

Aldosterone antagonists is what kind of diuretic ?

Answer 44

K sparing diuretic Works in Late distal and cortical collecting duct

Question 45

Aldosterone antagonists work on what receptors?

Answer 45

Mineralocorticoid receptor antagonists Work in Late distal and cortical collecting duct

Question 46

Aldosterone antagonists do what? | 2 examples?

Answer 46

Compete with aldosterone receptor sites which inhibits Na reabsorption & K secretion Spironolactone & eplerenone

Question 47

Na channel blockers work how? | 2 examples?

Answer 47

Inhibit entry of sodium into cell which reduces amount of sodium transported by Na-K ATPase Also reduces secretion of potassium as action of Na-K ATPase decreases Amiloride & triamterene

Question 48

Na channel blockers are what kind of diuretic?

Answer 48

K sparing diuretic ex: Amiloride and Triamterene Work in Late distal and cortical collecting duct

Question 49

Intercalated Cell Activity what is H+ ions secretion controlled by? in Late distal and cortical collecting duct

Answer 49

Secretion controlled by H-ATPase transporter

Question 50

In the Late distal and cortical collecting duct, Intercalated Cell Activity -- the H-ATPase transporter must have have the presence of what for conversion of CO2 and H2O into H+ ions and HCO3?

Answer 50

Presence of carbonic anhydrase allows conversion of CO2 and H2O to hydrogen ions and bicarb ions

Question 51

In the Late distal and cortical collecting duct, Intercalated Cell Activity -- how is Chloride secreted ?

Answer 51

Chloride also secreted following electrochemical gradient

Question 52

In the Late distal and cortical collecting duct, Intercalated Cell Activity - Bicarb is reabsorbed using what transport mechanism?

Answer 52

Bicarb reabsorbed using Cl-HCO3-counter-transport mechanism following the Cl-gradient into the cell

Question 53

In the Late distal and cortical collecting duct, Intercalated Cell Activity what is moved freely between cell and interstitial fluid?

Answer 53

CO2 moved freely between cell and interstitial fluid

Question 54

Meduallary Collecting Ducts reabsorb what % of filtered water and Na?

Answer 54

Reabsorb <10% of filtered water and sodium

Question 55

Meduallary Collecting Ducts determines what?

Answer 55

Determine final concentration of solutes and urine concentration

Question 56

Meduallary Collecting Ducts, Water permeability controlled by what?

Answer 56

ADH

Question 57

Meduallary Collecting Ducts how is Urea reabsorbed?

Answer 57

Urea is reabsorbed via specific urea transporters which moves urea into the interstitial spaces thus affecting osmolarity

Question 58

Meduallary Collecting Ducts secrete what ion?

Answer 58

Secretes hydrogen ions (like cortical collecting tubule)

Question 59

Change in solute concentration depends | on what vs what?

Answer 59

rate of reabsorption (secretion) versus rate of water reabsorption

Question 60

On the squiggly graph with all the different solutes -- what does inulin's line represent? - - what does a conc of 3 mean? - - what does a conc of 125 mean?

Answer 60

Inulin neither secreted or reabsorbed provides indication of water reabsorption Inulin conc of 3 means that 1/3 of water remains in tubule (2/3 has been reabsorbed) Inulin conc of 125 means 1/125 of water remains while 124/125 has been reabsorbed