Exam 3 Lecture - Regulation of Potassium

Question 1

What is the main intracellular cation?

Answer 1

potassium

Question 2

What is K important for inside of cells?

Answer 2

an important osmole, maintaining cell volume

Question 3

Why is K important extracellularly?

Answer 3

to avoid the affects of hypokalemia and hyperkalemia

Question 4

What is hypokalemia?

Answer 4

low levels of extracellular potassium

Question 5

What is hyperkalemia?

Answer 5

high levels or extracellular potassium

Question 6

Does the kidney regulate intracellular or extracellular potassium?

Answer 6

extracellular potassium

Question 7

How does hypokalemia affect the generation of action potentials?

Answer 7

it makes generating them harder because it makes the resting membrane potential lower

Question 8

How does hyperkalemia affect the generation of action potentials?

Answer 8

it makes generating action potentials easier, but Na levels inside of the cell are unable to reset, so the cell becomes less excitable

Question 9

What are symptoms associated with hypokalemia?

Answer 9

muscle weakness, respiratory problems, cardiac arrhythmia, renal dysfuntion

Question 10

What are symptoms associated with hyperkalemia?

Answer 10

muscle weakness and cardiac dysfunction

Question 11

Is hypokalemia or hyperkalemia worse?

Answer 11

hyperkalemia

Question 12

If enough K is not excreted, what will happen to the animal?

Answer 12

it will become hyperkalemic

Question 13

If too much K is excreted, what will happen to the animal?

Answer 13

it will become hypokalemic

Question 14

Where does the most K excretion occur?

Answer 14

in the kidney

Question 15

What is the kidney’s short term response to an altered K concentration outside of the cell?

Answer 15

translocation: sends K out to the ECF it is too low, sends K into the cell if ECF is too high

Question 16

What is translocation affected by?

Answer 16

insulin, catecholamines, acidosis/alkalosis

Question 17

What is insulin given to correct?

Answer 17

hyperkalemia

Question 18

How do catecholamines work?

Answer 18

they can move K in and out depending on whether they activate alpha or beta receptors

Question 19

What is bicarb administered to correct?

Answer 19

hyperkalemia

Question 20

How does insulin correct hyperkalemia?

Answer 20

it promotes movement of K into cells by stimulating NaKATPase

Question 21

What receptors are associated with catecholamines?

Answer 21

alpha and beta

Question 22

Do alpha receptors promote the movement of K into the cell or out of it?

Answer 22

out of it

Question 23

Do beta receptors promote the movement of K into the cell or out of it?

Answer 23

into it by stimulating NaKATPase

Question 24

What does acidosis promote in regards to potassium movement?

Answer 24

hyperkalemia - High H+ promotes movement of K out of the cells in order to maintain electroneutrality - but into the ECF

Question 25

What does alkalosis promote in regards to potassium movement?

Answer 25

hypokalemia - Low H+ moves K into cells - but into the ECF

Question 26

Under normal conditions what is the primary goal of the kidney in regards to K?

Answer 26

to retain it

Question 27

What function must the kideny have in order to maintain homeostasis?

Answer 27

to secrete K

Question 28

True or False: The proximal tubule can only secrete K.

Answer 28

False: the proximal tubule can only reabsorb K, it cannot secrete it

Question 29

How is K reabsorbed in the proximal tubule?

Answer 29

paracellularly and transcellularly

Question 30

Where can K be reabsorbed paracellularly in the proximal tubule?

Answer 30

only in the late proximal tubule

Question 31

How is K reabsorbed in the proximal tubule transcellularly?

Answer 31

by the K Cl symporter in the basolateral membrane ' there are probably K channels in the luminal membrane too'

Question 32

True or False: The distal tubule can only absorb K, and cannot secrete it

Answer 32

True

Question 33

How is K reabsorbed in the distal tubule?

Answer 33

paracellularly and transcellularly

Question 34

How is K reabsorbed transcellularly in the distal tubule?

Answer 34

via the NKCC1 transporter at the luminal membrane and K channels in the basolateral membrane

Question 35

Is K reabsorbed or secreted in the collecting ducts?

Answer 35

both

Question 36

Where is K secreted in the collecting ducts?

Answer 36

in the principle cells

Question 37

How is K secreted in the collecting ducts?

Answer 37

1. NaKATPase keeps intracellular K concentration high 2. Na enters viathe amiloride-sensitive channels making the lumen negative 3. K wants to move out of the cell and does so on the luminal side because it is more permeable to K (some does leave through the basolateral side

Question 38

What part of the collecting ducts reabsorb K?

Answer 38

the alpha intercalated cells

Question 39

How is K reabsorbed in the alpha intercalated cells?

Answer 39

1. H leaves the cell via HATPase, 2. H K ATPase brings K in at the luminal membrane 3. K then leaves at the basolateral membrane into the extracellular fluid

Question 40

What determines renal K excretion?

Answer 40

plasma K concentration, tubular flow rate, lumen electronegativity

Question 41

What does increased plasma concentration of K lead to?

Answer 41

the translocation into the ICF increasing the K gradient in renal cells and pushing K into the lumen also stimulates aldosterone

Question 42

How does aldosterone affect K excretion?

Answer 42

it stimulates Na reabsorption which means K is being pushed out of the cells (Na channels and K channels are increased)

Question 43

What does hyperaldosteronism lead to?

Answer 43

hypokalemia

Question 44

What does hypoaldosteronism lead to?

Answer 44

hyperkalemia

Question 45

How does decreased tubular flow rate affect K secretion?

Answer 45

it decreases it

Question 46

How does increased tubular flow rate affect K secretion?

Answer 46

it increases it

Question 47

How does increased lumen electronegativity affect K secretion?

Answer 47

it increases it

Question 48

How does decreased lumen electronegativity affect K secretion?

Answer 48

it decreases it

Question 49

How does Na intake affect renal handling of K?

Answer 49

increased dietary intake of Na leads to increase of tubular concentration therefore more Na reabsorption and more K secretion

Question 50

How do loop, thiazide, and osmotic diuretics affect renal handling of K?

Answer 50

increase the flow rate and Na concentration in CD which increases K secretion and can cause hypokalemia

Question 51

How do amiloride-like diuretics affect renal handling of K?

Answer 51

inhibit Na uptake in CD so inhibit K secretion; known as K sparing diuretics