Exam 3 - Lecture 40 (Regulation of K+)

Question 1

Why is K+ important in the EC space even though it is so low?

Answer 1

Bc it detects RMP

Question 2

What is the main IC cation?

Answer 2

K+

Question 3

What is hypokalemia?

Answer 3

Decreased ECF K+ levels

Question 4

What is hyperkalemia?

Answer 4

Increased ECF K+ levels

Question 5

What does K+ balance determine and why?

Answer 5

Behavior of all excitable cells because it is the major determinant of RMP

Question 6

What happens to AP during hypokalemia?

Answer 6

Harder to initiate

Question 7

What happens to AP during hyperkalemia?

Answer 7

Harder to repeat

Question 8

Between hypokalemia and hyperkalemia, which is more serious?

Answer 8

hyperkalemia

Question 9

What are the 4 symptoms of hypokalemia?

Answer 9

1. Muscle weakness
2. Respiratory problems
3. Cardiac arrythmia
4. Renal dysfunction (Polyuria/Polydypsia)

Question 10

What are the 2 symptoms of hyperkalemia?

Answer 10

1. Muscle weakness (e.g. cats cannot keep head up bc lack nuchal ligament)
2. Cardiac dysfunction

Question 11

What does insulin promote?

Answer 11

Movement of K+ into cells by stimulating Na+K+ATPase

Question 12

What 3 things regulate external and internal balance of K+?

Answer 12

1. Insulin
2. Epinephrine
3. Acidosis/Alkalosis

Question 13

What does epinephrine promote?

Answer 13

Movement of K+ into cells AND out of cells thru adrenergic receptors

Question 14

How does epinephrine promote movement of K+ into cells?

Answer 14

Thru beta-2 stimulation of Na+K+ATPase

Question 15

How does epinephrine promote movement of K+ out of cells?

Answer 15

Thru alpha stimulation of Na+K+ATPase

Question 16

What do alkalosis/acidosis promote?

Answer 16

Alkalosis = low [H+] = moves K+ into cells
Acidosis = high [H+] = moves K+ out of cells

Question 17

Acidosis = _____kalemic

Answer 17

hyper

Question 18

Alkalosis = _____kalemic

Answer 18

hypo

Question 19

Tomcats are _____kalemic when blocked because EC K+ levels build up.

Answer 19

hyper

Question 20

___% of K+ reabs. happens in the PT.

Answer 20

67%

Question 21

Lumen positive PD moves K+ via _____ route in the PT and DST.

Answer 21

paracellular

Question 22

Which statement about ECF [K+] is most accurate?

A) ECF [K+] is higher than that of ICF
B) Insulin will increase ECF [K+]
C) Acidemia (decreasing ECF pH) is likely to lower ECF [K+]
D) Increased dietary K+ will decrease ECF [K+]
E) Oliguria (low urine output) may increase ECF [K+]

Answer 22

E) Oliguria (low urine output) may increase ECF [K+]

Question 23

What is oliguria?

Answer 23

low urine output

Question 24

___% of K+ reabs. happens in the DST.

Answer 24

20%

Question 25

How does Cl- move in the DST?

Answer 25

Paracellularly AND transcellularly (by NKCC1)

Question 26

Loop diuretics can cause _____.

Answer 26

hypokalemia

Question 27

What are the 3 steps by which the CD’s principal cells regulate K+?

Answer 27

1. Na+K+ATPase generates Na+ gradient
2. Na+ enters cell via amiloride sensitive Na+ channels
3. K+ leaves thru K+ channels down K+ gradient

Question 28

What happens to K+ in alpha-intercalated cells?

Answer 28

Absorption

Question 29

What 3 things determine renal K+ excretion?

Answer 29

1. Plasma [K+]
2. Tubular flow rate
3. Lumen electronegativity

Question 30

What happens when there is increased plasma [K+]?

Answer 30

More K+ enters cell, more leaves by luminal membrane and vice versa

Question 31

When is aldosterone stimulated?

Answer 31

When ECF [K+] is elevated

Question 32

What 3 things does aldosterone do when ECF K+ is elevated?

Answer 32

1. Increases Na+K+ATPase
2. Increases Na+ channels
3. Increases K+ channels

Question 33

What is hyperaldosteronism and what does it do/lead to in regards to K+?

Answer 33

Elevated aldosterone release; more K+ moves into the cell –> hypokalemia

Question 34

What is hypoaldosteronism and what does it do/lead to in regards to K+?

Answer 34

Lowered aldosterone release; less K+ moves into the cell –> hyperkalemia

Question 35

What happens to tubular flow rate of K+ during diuresis/antidiuresis?

Answer 35

Diuresis = ADH increases perm. of lum. mem. to K+
Antidiuresis = ADH decreases perm. of lum. mem. to K+

Question 36

What is lumen electronegativity?

Answer 36

How negative tubular fluid is

Question 37

What happens to K+ when LE is increased?

Answer 37

K+ secretion increases

Question 38

What happens to K+ when LE is decreased?

Answer 38

K+ secretion decreases

Question 39

What is an example of a drug that increases LE?

Answer 39

Penicillin

Question 40

How does Na+ intake affect renal handling of K+?

Answer 40

If there is too much Na+ in the diet, more Na+ is reabs. so more K+ is excreted.

Question 41

How does acidosis affect renal handling of K+?

Answer 41

It makes the basolateral mem. more permeable to K+, so K+ leaves at BLM and secretion is inhibited.

Question 42

How does alkalosis affect renal handling of K+?

Answer 42

It makes the BLM less permeable to K+, so K+ does not leave and is excreted.

Question 43

How do loop diuretics affect renal handling of K+?

Answer 43

Cause hypokalemia so promote K+ secretion

Question 44

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

Answer 44

Inhibit Na+ channel on lum. mem., less K+ is excreted but does not result in hypokalemia

Question 45

Which of the following could lead to hypokalemia?

A) Increased aldosterone secretion
B) Amiloride-like diuretics
C) Decreased lumen electronegativity
D) Low tubular flow rate

Answer 45

A) Increased aldosterone secretion

Question 46

Bartter’s syndrome is a genetic disroder that causes a dysfunctional, impaired NKCC1. What can be a result?

A) Hypokalemia
B) Hyperkalemia

Answer 46

A) Hypokalemia