Mechanisms to Adjust Urine Conc

Question 1

TF:U = 1

Answer 1

The concentration of the substance in the tubule is the same as the plasma

Question 2

The TF:U greater than 1

Answer 2

Substance is reabsorbed to a lesser extent than water

Question 3

TF:U less than 1

Answer 3

Substance is reabsorbed more avidly than water

Question 4

The loop of henle descending limb thin segment is permeable to? But impermeable to what

Answer 4

Water; NaCl which becomes more concentrated during descent

Question 5

The primary cilia does what

Answer 5

Senses changes in osmolarity

Question 6

The loop of henle ascending limb is permeable to what? Impermeable to what

Answer 6

NaCl (serves to dilute gradient); water

Question 7

What is the main transporter in the thick ascending limb that we care about

Answer 7

NKCC and NaH antiporter

Question 8

What ion drives luminal electrical voltage

Answer 8

K

Question 9

What diuretics act on the thick ascending loops

Answer 9

Loop diuretics

Question 10

When the luminal positive potential is reduced absorption of what is affected

Answer 10

Mg, Ca

Question 11

The early segment of the distal tubule is permeable to what? Impermeable?

Answer 11

Na, Cl, Ca; water

Question 12

The late segment of the distal tubule contains what cell types

Answer 12

Principal and intercalated

Question 13

What do principal cells do

Answer 13

Na and water reabsorption; K secretion

Question 14

What do intercalated cells do

Answer 14

Acid/base balance

Question 15

What diuretics act on the early distal tubule and what transporter do they act on

Answer 15

Thiazide diuretics; NCC transporter

Question 16

What diuretics act on the late segment DT principal cells?

Answer 16

Aldosterone antagonists and ENaC

Question 17

What is more specific and binds tighter than spironolactone

Answer 17

Eplerenone

Question 18

What diffuses down its gradients in the late segment DT of principle cells

Answer 18

Na, K, Cl

Question 19

α intercalated cells function to change pH by doing what

Answer 19

Secrete H and resorb HCO3 during acidosis

Question 20

Late segment DT β intercalated cells function in what

Answer 20

Alkalosis

Bicarb is secreted; H reabsorbed

Question 21

What does water and chloride normally follow in the nephron

Answer 21

Na

Question 22

Where is Cl active reabsorption

Answer 22

NaCl co-transporter (distal tubule)

Na-K-2Cl co-transporter (TAL)

Question 23

What inhibits NaCl co-transporter

Answer 23

Thiazide in the distal tubule

Question 24

What inhibits the NKCC co-transporter

Answer 24

Loop diuretics in the thick ascending loop

Question 25

Na reabsorption causes what

Answer 25

Water reabsorption and increased lumen negative potential, increased luminal Cl concentration, increased luminal urea concentration Which causes passive Cl and urea reabsorption

Question 26

What 3 spaces are regulated independently to concentrate urine

Answer 26

Tubular space, vascular space, interstitial space

Question 27

What two things function to concentrate the urine

Answer 27

Counter current multiplier and exchanger

Question 28

What is the single effect

Answer 28

NaCl leaves the ascending loop where water is impermeable

Question 29

What is fluid flow

Answer 29

Descending limb and collecting duct leak water to try and dilute the interstitium

Question 30

What determines the size of the gradient in the nephron

Answer 30

Length of the loop of henle

Question 31

The passive reuptake of water from interstitium is called

Answer 31

Countercurrent exchange

Question 32

What are the transporters of urea in the medullary CD

Answer 32

UT-A1 and UT-A3

Question 33

What are the urea transporters in the thin limb

Answer 33

UT-A2

Question 34

What are the urea transporters activated by

Answer 34

ADH

Question 35

If you eat high protein what is the urea conc in the medulla? Low protein?

Answer 35

High urea, low

Question 36

What is the location in which urea is reabsorbed mostly

Answer 36

thick ascending limb

Question 37

What 2 things lead to the salty medulla

Answer 37

NaCl and urea

Question 38

How do we calculate obligatory urine volume

Answer 38

Minimum solute exretion per day / max urine concentrating ability

Question 39

Antidiuresis requires high ____ and high ______ of the renal medullary intersitial fluid

Answer 39

ADH; osmolality

Question 40

What is the contribution of urea and NaCl the hyperosmolality of the medulla

Answer 40

50/50

Question 41

High levels of ADH leaves to high levels of permeability of what

Answer 41

Water at the collecting duct and NA in the thick ascending limb

Question 42

An increase/decrease in blood flow dissipates the medullary gradient

Answer 42

Increase

Question 43

Reduced O2 causes what in the medullary interstitium

Answer 43

Reduced medullary gradient

Question 44

What 2 things cause a decrease in the medullary gradient

Answer 44

Decreased blood (O2 reduction) and increased vasa recta flow

Question 45

Where does ADH start changing the Osm

Answer 45

Medullary collecting duct on

Question 46

How do you calculate osmolar clearance

Answer 46

U_osm * V / P_osm

Question 47

How do you calculate free water clearance

Answer 47

C_h2o = V - C_osm

Question 48

When C_h2o is negative? Positive?

Answer 48

Excess solute removed and water is conserved; water is being excreted forming dilute urine

Question 49

How do you calculate fractional excretion

Answer 49

Clearance_x / GFR

Question 50

What does it mean when fractional excretion is greater than 1? Less than?

Answer 50

Secreted; reabsorbed

Question 51

What if the fractional excretion of Na is below 1%? Above 2?

Answer 51

Pre-renal; intra or post renal

Question 52

What does SIADH result in

Answer 52

Euvolemic hyponatremia

Question 53

What causes SIADH to give you euvolemic hyponatremia

Answer 53

ADH is secreted when it isn’t supposed to —> compensatory mechanisms —> volume and Na excreted

Question 54

What are the possible causes euvolemic hyponatremia

Answer 54

SIADH, COPD, malignancy

Question 55

What are some common causes of hypervolemic hyponatremia

Answer 55

CHF, renal impairment, cirrhosis

Question 56

What is central diabetes insipidus

Answer 56

Deficient secretion of ADH from hypothalamus or pituitary

Question 57

What is nephrogenic diabetes insipidus

Answer 57

Lack of renal response to ADH

Question 58

What are the symptoms of diabetes insidpidous

Answer 58

Polyuria, polydipsia, polyphagia

Question 59

How do you differentiate diabetes insipidus cases

Answer 59

ADH challenge test Inject ADH and see if the body responds appropriately