V: Potassium Balance

Question 1

Postassium balance has to be kept

Answer 1

CONSTANT

Question 2

% K+ in ICF

Answer 2

98%

Question 3

% K+ in ECF

Answer 3

2%

Question 4

Hyperkalemia values

Answer 4

K+ > 5meq/L

Question 5

Hypokalemia values

Answer 5

K+ < 3.5meq/L

Question 6

Consequences of hyperkalemia and hypokalemia

Answer 6

Weakness
Paralytic ileus
Cardiac arrythmia

Question 7

Internal K+ balance depends on

Answer 7

Hormones
Drugs
Pathological state

Question 8

External K+ balance is

Answer 8

Urinary K+ excretion = Dietary K+

Question 9

What 3 hormones released after K+ ingestion

Answer 9

Insulin
Catecholamines
Aldosterone

Question 10

Insulin effect

Answer 10

Stimulates K+ uptake through increase in Na+/KATPase

Question 11

Sympathetic nervous system effect

Answer 11

Through B2 receptors, increase in Na+/K+ATPase

Question 12

Increase in Na+/K+ATPase promote

Answer 12

K+ into the cell which can result in HYPOKALEMIA

Question 13

On the other hand, a receptors cause

Answer 13

K+ to move out of cell and cause Hyperkalemia

Question 14

Aldosterone effect

Answer 14

Increases Na+/K+ATPase

Question 15

Not pathological situations where an alteration in extracellular K+ may occur due to disturbance in internal K+ balance

Answer 15

Exercise as K+ moves out of cells
Acid-base abnormalities, H+/K+ exchange. As H+ leaves the cell, K+ has to accompany it, leading to disturbance in external balance

Question 16

During alkalemia
pH
[H+] blood
H+ movement
K+ movement

Answer 16

pH>7.45
[H+] decreased
H+ moves out of cells
K+ enters cells

Question 17

During acidemia 
pH
[H+] blood
H+ movement
K+ movement

Answer 17

pH<7.35
[H+] increased
H+ into cells
K+ leaves cells

Question 18

K+ movement compared to H+

Answer 18

K+ follows the opposite movement from H+

Question 19

Shift of K+ during hyperosmolarity

Answer 19

Hyperosmolarity is when there a decrease in H2O

H2O leaves the cell and drags K+ along with it

Question 20

Cell lysis effect on K+

Answer 20

Releases K+ causing hyperkalemia

Question 21

Agonist vs antagonist

Answer 21

Agonist is a drug that binds to its receptor to produce a similar response
Antagonist does not allow receptor to follow response

Question 22

K+ shifts into cell: HYPOKALEMIA

Answer 22

Insulin 
B-2 Adrenergic agonist
A-adrenergic antagonist 
Alkalosis 
Hyposmolarity (too much H2O)

Question 23

K+ shifts out of cell: HYPERKALEMIA

Answer 23

Insulin deficit
B-2 Adrenergic antagonist
Acidosis
Hyperosmolarity (decrease H2O)
Cell lysis 
Exercise

Question 24

Why are external balance mechanisms flexible

Answer 24

Because K+ varies a lot

Question 25

K+ handled in nephron through

Answer 25

Filtration Reabsorption Secretion

Question 26

in FILTRATION of K+

Answer 26

It is not bound to plasma so freely filters

Question 27

In REABSORPTION of K+ in PCT and TAL

Answer 27

PCT absorbs 67% of filtered K+ | TAL absorbs 20%

Question 28

Which part of nephron is responsible for adjustments in K+ when dietary K+ changes

Answer 28

Distal tubules and collecting ducts

Question 29

In a low K+ diet, which cells involved

Answer 29

K+ is reabsorbed (because there is not many so we want to reabsorb it all) by A-INTERCALATED CELLS

Question 30

Urinary K+ excretion in a low K+ diet

Answer 30

<1%

Question 31

On a high K+ diet, which cells are involved

Answer 31

K+ secreted by PRINCIPAL CELLS (K+ passes to renal tube from capillaries)

Question 32

Urinary K+ excretion at high protein diets

Answer 32

As high as 110%

Question 33

Reabsorption in proximal convoluted tubule and thick ascending limb is

Answer 33

CONSTANT under most conditions

Question 34

Excretion in late distal tubule and collecting ducts is

Answer 34

VARIABLE because they perform fine-tuning of K+ excretion to maintain K+ balance

Question 35

Type A cells function

Answer 35

During HYPOKALEMIA/ACIDOSIS K+ reabsorption by a-intercalated cells H+ secretion

Question 36

Type B cells function

Answer 36

During HYPERKALEMIA/ALKALOSIS H+ reabsorption K+ secreted by B-intercalated cells

Question 37

H+ and K+ secretion/reabsorption

Answer 37

Is the opposite | If H+ is reabsorbed (HYPERKALEMIA/ALKALOSIS) then K+ is secreted

Question 38

Magnitude of K+ secretion determined by

Answer 38

Size of electrochemical gradient for K+

Question 39

Aldosterone, acid-base disturbances, dietary K+ all increase

Answer 39

Impact secretion of K+

Question 40

Dietary K+ process

Answer 40

``` Increase in intracellular K+ Increase in K+ in intercalated cells HYPERKALEMIA (Type B intercalated cells) K+ increased SECRETION Increased K+ in urine ```

Question 41

Aldosterone effect on Na+

Answer 41

Increases Na+ reabsorption by inducing Na+/K+ATPase | Increased K+ secretion

Question 42

What channels does an increase K+ impact (HYPERKALEMIA)

Answer 42

Na+/K+ATPase | ROMK channels

Question 43

High Na+ diet impact on K+

Answer 43

Increase in Na+ to principal cells Increase Na+ extruded from cell through Na+/K+ATPase pumps Increase K+ into cell Increase K+ excretion

Question 44

What are diuretics

Answer 44

Pills that reduce Na+ and H2O | Block Na+ reabsorption

Question 45

Impact of diuretics in K+

Answer 45

Diuretics block Na+ reabsorption | Increase K+ excretion

Question 46

What do diuretics block

Answer 46

Aldosterone function (which is to increase Na+/K+ATPase)

Question 47

Increase flow rate impact on K+ secretion

Answer 47

Increase flow rate increases K+ secretion | More flow = more diluted K+

Question 48

During acidosis and alkalosis, impact on K+ flow

Answer 48

Acidosis (high H+ in blood) = K+ out of cell | Alkalosis (low H+ in blood) = K+ into cell

Question 49

During acidosis, which pump is inhibited

Answer 49

Na+/K+ATPase so K+ leaves the cell to maintain neutrality = hypokalemia

Question 50

During alkalosis, movement of H+ and K+

Answer 50

H+ leaves the cell for buffering | K+ enters to maintain electroneutrality which causes hypokalemia

Question 51

Main external buffer systems

Answer 51

Bicarbonate and phosphate

Question 52

In volume depletion, aldosterone stimulates

Answer 52

Na+ retention without K+ secretion

Question 53

In hyperkalemia there is stimulation of

Answer 53

K+ secretion w/ salt retention

Question 54

During hypovolemia, mechanism of AngiotensinII

Answer 54

In hypovolemia we want to increase Na+ reabsorption (bc H2O follows it) to increase extracellular volume Angiotensin II --> Aldosterone Aldosterone will increase ENaC, so more Na+ rebasorbed Angiotensin II will promote Na+/Cl- cotransport Angiotensin II will inhibit ROMK, K+ secretion

Question 55

During hyperkalemia, aldosterone and angiotensin II effect

Answer 55

We want to decrease K+ in cell, so K+ excretion Aldosterone will promote ENaC and ROMK, Na+ and K+ secretion Angiotensin II will block Na+/Cl- cotransport

Question 56

Where is the Na+/Cl- cotransporter

Answer 56

In early distal convoluted tubules