Integrative Physiology II

Question 1

ECF K+ tightly regulated

at — meq/L.

Answer 1

4.2

Question 2

Increase of only 3 to 4

mEq/L can cause (3)

Answer 2

cardiac
arrhythmias, cardiac
arrest, or fibrillation.

Question 3

Mechanisms controlling K+

Homeostasis (2)

Answer 3

1. Control of K+ distribution
   between the ECF and ICF
2. To keep [K+]ECF constant; rate of K+ excretion must equal rate of K+ input.

Question 4

High [K+ ]ECF:

Answer 4

Hyperkalemia

Question 5

Low [K+ ]ECF:

Answer 5

Hypokalemia

Question 6

Factors That Shift K+ Into Cells (decrease [K+]ECF) (7)

Answer 6

insulin
aldosterone 
beta2 adrenergic stimulation
alkalosis
decrease ECF osm 
increase na/k ATPase activity 
dilute ICF, decrease ΔEC for diffusion out of K+ cell

Question 7

Factors That Shift K+ Out of Cells (increase [K+]ECF) (8)

Answer 7

increased insulin deficiency 
aldosterone deficiency
beta2 adrenergic antagonists 
acidosis
increase ECF osm 
strenuous exercise 
decrease Na+/K+ ATPase Activity
concentrate ICF, increase ΔEC for diffusion out of cell

Question 8

Acidosis =

Answer 8

Hyperkalemia

Question 9

Alkalosis =

Answer 9

Hypokalemia

Question 10

Three Factors in Tubular Processing of K+

Answer 10

(Filtration; Reabsorption; Secretion)

Question 11

Day to Day regulation of [K+]ECF is function of

Answer 11

late Distal Tubule/Collecting Duct

Question 12

High K+ intake increases

Answer 12

K+ secretion (principal cells)

Question 13

Low K+ intake increases

Answer 13

K+ reabsorption (alpha intercalated cells)

Question 14

Factors that Determine Rate of K+

Secretion by Principal Cells (3)

Answer 14

1. Na+/K+ ATPase Activity
2. Transepithelial potential difference
   (TEPD) between blood and lumen
3. Permeability of apical membrane for K+

Question 15

Factors that Control Principal Cell K+ Secretion

 Results in increased K+ Secretion (4)

Answer 15

1. increase [K+]ECF
2. increase Aldosterone
3. increase Distal Tubule Flow Rate
4. Acid/Base Status

Question 16

Alkalosis –

Answer 16

increase K+ Secretion

Question 17

Acidosis –

Answer 17

decrease K+ secretion

Question 18

↑[K+]ECF Increases K+ Secretion

Mechanisms (4)

Answer 18

1. increase Na+/K+ ATPase activity
2. TEPD is more lumen
   negative (due to increased
   Na+ reabsorption) which
   favors K+ secretion
3. increase # K+ channels in apical
   membrane
4. Stimulates aldosterone
   secretion.

Question 19

Increased Distal Tubule Flow Rate: increase K+ Secretion

Causes (3)

Answer 19

 increase ECF volume
 Na+ loading
 Some Diuretics

Question 20

Increased Distal Tubule Flow Rate: increase K+ Secretion

Mechanisms (2)

Answer 20

1. Increased tubule flow rate keeps 
luminal K+ lower, maintaining ΔC for 
secretion
2. Increases #BK channels in apical 
membrane

Question 21

Causes of Hyperkalemia (5)

Answer 21

Renal failure
 Decreased distal nephron flow (heart failure, severe
volume depletion, NSAID, etc.)
 Decreased aldosterone or decreased effect of
aldosterone
 Metabolic acidosis (hyperkalemia is mild)
Diabetes (kidney disease, acidosis, decreased insulin)

Question 22

Decreased aldosterone or decreased effect of

aldosterone: (3)

Answer 22

• adrenal insufficiency
• resistance to aldosterone
• K+ sparing diuretics (spironolactone)

Question 23

Causes of Hypokalemia (6)

Answer 23

Very low intake of K +
GI loss of K+ - diarrhea
Metabolic alkalosis
Excess insulin
Increased distal tubular flow
Excess aldosterone

Question 24

Increased distal tubular flow: (3)

Answer 24

• salt wasting nephropathies
• osmotic diuretics
• loop diuretics

Question 25

Diuretic is a

Answer 25

drug that increases urine volume output.

Question 26

Most diuretics act by

Answer 26

decreasing Na+ reabsorption from some | part of the nephron.

Question 27

Natriuresis causes

Answer 27

diuresis by an osmotic mechanism.

Question 28

Natriuresis also affects reabsorption of (3)

Answer 28

Cl-, K+, and other | electrolytes.

Question 29

Most common reason for use of diuretics is to (3)

Answer 29

reduce ECFV (extracellular fluid volume). – Reduces edema – Reduces MAP (mean arterial pressure)

Question 30

Diuretics Increase Solute and H2O Excretion until

Answer 30

Compensatory Mechanisms Re- establishes Balance

Question 31

--- Transport is a Target | for many Diuretics

Answer 31

Na+ (Where goes the Na+ goes the H2O)

Question 32

Osmotic Diuretics

Answer 32

Nonabsorbable substance is filtered (ex. mannitol, | sucrose).

Question 33

Osmols in tubular fluid require ---.

Answer 33

water

Question 34

Osmotic Diuretics | Similar to effects of

Answer 34

endogenous substances (glucose, urea). - Diuresis caused by hyperglycemia.

Question 35

Osmotic Diuretics | May increase excretion of

Answer 35

other solutes.

Question 36

Carbonic Anhydrase Inhibitors (3)

Answer 36

``` Acetazolamide. More than 80% of HCO3- reabsorption and H+ secretion occurs in proximal tubule. CA inhibitors block Na+ reabsorption (and H+ secretion) indirectly. ```

Question 37

Loop Diuretics |  ex (3)

Answer 37

Furosemide, ethacrynic acid, | bumetanide

Question 38

Loop Diuretics | Inhibit

Answer 38

Na+-K+-2Cl- - cotransport pump on luminal membrane of TAL of Henle.

Question 39

Loop Diuretics | Most powerful

Answer 39

diuretics available (30% of GFR may appear in urine!).

Question 40

Loop Diuretics Overwhelm downstream --- capacity.

Answer 40

absorptive

Question 41

Loop Diuretics | Disrupt

Answer 41

countercurrent | multiplier.

Question 42

Thiazide Diuretics |  ex (2)

Answer 42

Hydrochlorothiazide, | chlorthalidone, etc.

Question 43

Thiazide Diuretics | Block

Answer 43

Na+-Cl- cotransport mechanism in early distal tubule

Question 44

Thiazide Diuretics More distal tubular segments have limited ability to

Answer 44

respond to increased load of Na+, Cl-, H2O.

Question 45

class: Osmotic (mannitol) mechanism: site of aciton:

Answer 45

↑ osmolarity of tubular fluid Mainly proximal tubule

Question 46

class: Loop (furosemide) mechanism: site of aciton:

Answer 46

↓ Na-K-2Cl cotransport | TAL of Henle

Question 47

class: Carbonic anhydrase inhibitor (acetazolamide) mechanism: site of aciton:

Answer 47

↓ H+ secretion, HCO3- ab- sorption (↓Na-H exchange) Proximal tubule

Question 48

class: Thiazide (hydrochlorothiazide) mechanism: site of aciton:

Answer 48

↓ Na-Cl cotransport | Early distal tubule

Question 49

class: Aldosterone antagonists (spironolactone) mechanism: site of aciton:

Answer 49

↓ Na+ absorption & K+ secretion Late distal & Collecting tubule

Question 50

class: Na channel blocker (triamterene) mechanism: site of aciton:

Answer 50

Block ENaC & ↓ K+ secretion Late distal & Collecting tubule

Question 51

K+ Sparing Diuretics (2)

Answer 51

Aldosterone antagonists (spironolactone) Na channel blocker (triamterene)

Question 52

Many Diuretics Cause K+ Loss (Hypokalemia) (3)

Answer 52

```  Increasing flow rate of filtrate through distal nephron decreases K+ reabsorption.  Keeps luminal K+ concentration low supporting secretion  Hypokalemia may result. ```

Question 53

``` Aldosterone antagonists reduce levels of (3) ```

Answer 53

Na+/K+ ATPase, | ENaC, K+ channel.

Question 54

ENaC blockers reduce | 3

Answer 54

Na+ uptake, Na+/K+ | activity, K+ secretion