Regulation Of Potassium Balance

Question 1

What is the normal range for K+?

Answer 1

3.5-5.0 mEq/L

Question 2

Where is the majority of K+ stored in the human body?

Answer 2

Intracellularly

More specifically in muscle cells (80%)

Question 3

What are some causes of hypokalemia?

Answer 3

Vomiting/diarrhea
Insulin excess
Alkalosis
Deficiency

Question 4

What are some causes of hyperkalemia?

Answer 4

Excessive intake
Tissue release (rhabdo, burns, hemolysis)
Shifts from ICF to ECF (acidosis, insulin deficiency, tissue damage, hyperglycemia)

Question 5

What is pseudohyperkalemia?

Answer 5

Artificially high plasma [K+] due to lysis of RBCs while blood is drawn

Question 6

What are the major routes of potassium loss from the body?

Answer 6

Most is through the kidneys/urine

The rest is through feces

Question 7

What occurs to the resting membrane potential when the person is hyperkalemic?

Answer 7

The resting membrane potential hypopolarizes, making it more likely to fire

Question 8

What occurs to the resting membrane potential in a patient with hypokalemia?

Answer 8

The resting membrane potential hyperpolarizes, making it more difficult to fire an AP

Question 9

What is a classic sign of hypokalemia in an EKG?

Answer 9

Low T-wave

Question 10

What is a classic sign for hyperkalemia on an EKG?

Answer 10

A high peaked T-wave

Question 11

What is the adequate intake of Calcium to ensure nutritional needs?

Answer 11

~1000mg/day

Better to split the 1000 up for better absorption

Question 12

What groups are at highest risk of calcium deficiency?

Answer 12

Adolescents, postmenopausal women, vegetarians, lactose intolerant

Question 13

What are the 3 methods of acquiring calcium?

Answer 13

Intestinal absorption

Renal tubular reabsorption

Internal redistribution from bone

Question 14

How is calcium disposed of from the body?

Answer 14

Lost through stool, urine, and distribution into bone

Question 15

What is the total plasma level of calcium?

Answer 15

5.0 mEq/L

Question 16

What occurs to muscle in relation to hypocalcemia?

Answer 16

Increases neuromuscular excitability

Question 17

What occurs to muscle in relation to hypercalcemia?

Answer 17

Depresses neuromuscular excitability

Question 18

How much is required for daily phosphorus dietary intake?

How much is actually absorbed?

Answer 18

~1500 mg

~900 mg

Question 19

Where is most of phosphate stored in the body?

Answer 19

85% is stored in the bone

Question 20

How is phosphate disposed of from the body?

Answer 20

Through stool, urine, and distribution into bone

There’s very little actively in circulation

Question 21

What are the 4 main regulators of phosphate metabolism?

Answer 21

Dietary phosphate intake

Calcitriol (increases phosphorus resorption)

PTH (resorbs from bone)

Renal tubular reabsorption

Question 22

Where is most of Mg2+ stored in the body?

Answer 22

50% in bone

With 49% in ICF (especially muscle) and 1% in ECF

Very little actively circulates

Question 23

What is the total serum Mg2+ level?

How about free serum Mg2+?

Answer 23

1. 8-2.2 mg/dL

0. 8-1.0 mEq/L

Question 24

What effect does epinephrine have on potassium?

Answer 24

It lowers serum K+ by uptake into cells of extrarenal tissues while stimulating potassium excretion by the kidney

DECREASES SERUM K+

Question 25

What is the effect of insulin on potassium?

Answer 25

It stimulates Na-K ATPase causing a flux of K+ into cells and efflux of Na+ from cells

INCREASES INTRACELLULAR K+

Question 26

What effect does aldosterone have on potassium?

Answer 26

Renal: INCREASES K+ EXCRETION

Extrarenal: INCREASES K+ SECRETION INTO INTESTINAL FLUIDS AND SALIVA

Question 27

What do insulin and catecholamines stimulate?

Answer 27

They both upregulate the Sodium-Hydrogen exchanger, the NKCC, and Na-K ATPase

This promotes a net effect of bringing potassium in and pumping hydrogen out

Question 28

What is the major mechanism in the proximal tubule?

Answer 28

The Na-K ATPase in the basolateral membrane

Question 29

How is potassium reabsorbed in the proximal tubule?

Answer 29

Because Na gets reabsorbed with HCO3, Cl- gets left behind creating a negative transepithelial difference (TEPD), which eventually repels Cl too, causing it to get reabsorbed

This NaCl reabsorption leads to water following along and creating a positive TEPD, which then begins to repel K+, so it moves paracellularly

Question 30

Where is potassium secreted and reabsorbed?

Answer 30

In the late DT and cortical CD

Question 31

What do principal cells and beta-intercalated cells do with potassium

Answer 31

They secrete it into the tubular lumen

Stimulated by increased ECF [K+], aldosterone, and increased tubular flow rate

Question 32

What do alpha-intercalated cells do with potassium?

Answer 32

They reabsorb it

Stimulated by K+ deficiency, low K+ diet, hypokalemia, or K+ loss through SEVERE diarrhea

Question 33

If there is an increased distal tubular flow rate, what occurs to potassium?

Answer 33

It enhances K+ secretion

And vice versa

Question 34

If there is acute alkalosis, how does this affect K+ levels?

Answer 34

There is increased activity of the Na-K ATPase pump, which leads to increased potassium secretion and therefore HYPOKALEMIA

Question 35

If there is acute acidosis, what is the affect on K+ levels?

Answer 35

There is decreased activity of the Na-K ATPase pump and decreases K+ secretion and therefore HYPERKALEMIA

Question 36

What is the difference between acute and chronic acidosis?

Answer 36

Chronic acidosis stimulates K+ secretion

Question 37

What effect does ADH have on K+?

Answer 37

Increased K+ secretion

Question 38

What effect does luminal flow rate have on K+?

Answer 38

Increased flow rate = increased K+ secretion

Question 39

What effect do glucocorticoids have on K+?

Answer 39

Increased K+ secretion

Question 40

If there is an increase in NaCl reabsorption, what occurs to K+ levels?

Answer 40

There is a decrease in K+ secretion due to the decrease of the negative TEPD