2. DSA Intro to Regulation of K, Ca, P, Mg Balance

Question 1

What is the normal plasma concentration of K+?

Answer 1

3.5-5.0mEq/L

Question 2

98% of K is intracellular while 2% is extracellular, this 30fold difference is due to the NaKATPase and NKCC2 transporters. How is the ICF K+ divided and what is the input and out put?

Answer 2

ICF divided into muscle cells =80% and 20% other cells

intake of K equals output of K+ via 10% stool and 90% urine

Question 3

What occurs when plasma K concentration is below 3.5, commonly caused by vomitting/diarrhea, insulin excess, and dietary deficiency?

Answer 3

hypokalemia

Question 4

What occurs when K+ [plasma] is about 5.0, commonly caused by excessive dietary intake of K+, tissue release, and shifts from ICF to ECF?

Answer 4

Hyperkalemia

Question 5

What is pseudohyperkalemia?

Answer 5

artificially high plasma K due to lysis of RBCs while blood is drawn

Question 6

A majority of K+ is stored in muscle, liver, bone, and RBCs. The majority is lost via?

Answer 6

feces (10mmol/day) and urine (60mmol/day)

Question 7

Regarding skeletal muscle, hypokalemia hyperpolarizes the membrane resting potential, making it more negative and less likely to start an AP. How about hyperkalemia?

Answer 7

Hyperkalemia raises the resting membrane potential to be less negative, making it easier to start and AP/ muscle contraction

Question 8

The cardiac conduction system responds in the opposite direction compared to skeletal muscle. So hyperkalemia makes the RMP hyperpolarized, meaning it would be harder to start an AP. What would hypokalemia do?

Answer 8

would make it easier to activate an AP, leading to tachycardia

Question 9

Low T-wave in hypokalemia and what is seen in hyperkalemia?

Answer 9

a high peaked T wave

Question 10

Hyperosmolality, alkalosis, B-catecholamines, and insulin all do what to K+ cell uptake?

Answer 10

INCREASE/ENHANCE

Question 11

A-catecholamines, acidosis, and cell damage all do what to K+ cell uptake?

Answer 11

DECREASE/IMPAIR

Question 12

What does external potassium balance do to K+?

Answer 12

loose correlation

Question 13

What is the normal range of dietary Ca2+ intake?

Answer 13

1000mg/day for adults

Question 14

Calcium is absorbed via the GI tract, renal tubular reabsorption via calcitriol and PTH, internally redistributed in bone, and how is Ca2+ lost?

Answer 14

through stool and urine, 80/20%

all intake will be output

Question 15

Hypocalcemia increases neuromuscular excitability (d/t shorter contraction?) while hypercalcemia decreases nueromuscular excitability. This is regulated via what 3 things?

Answer 15

PTH, Calcitonin, Calcitriol

Question 16

Primary hyperparathyroidism and malignancy would lead to what?

Answer 16

elevated serum calcium

Question 17

Low serum calcium would lead to what three things?

Answer 17

hypothyroidism
renal disease
Vit D deficiency

Question 18

What is the normal range of dietary Phosphate?

Answer 18

1500mg/day

Question 19

85% of phophate is stored in the bones, while 14% is stored in cells and 1% in serum. It is lost via?

Answer 19

lost via stool and urine, more in urine, equal input to output

Question 20

The four main regulators of phosphate metabolism are dietary, calcitriol, PTH, and renal tubular. How is dietary one?

Answer 20

via phosphate intake and absorption

Question 21

How does calcitriol regulate phosphate metab?

Answer 21

increases phosphorus resorption from bone and absorption from intestine

Question 22

How does PTH regulate phosphate metab?

Answer 22

phosphorus resorption directly from bone, indirectly activates instestinal absorption through stimulation of calcitriol production

Question 23

how does renal tubular reabsorption regulate phosphate metab?

Answer 23

by reabsorption stimulated by tubular filtered load of phosphorus and inhibited by PTH

Question 24

Magnesium (mg) is almost in every biochemical process in the cell. When depleted it is associated with migraine, depression epilepsy SIDS, and muscle cramps. Where is it stored and how is it excreted?

Answer 24

50% stored in bone, 49% stored in ICF in muscle 1%ECF

intake = output, more via feces

Question 25

Total serum mg is 1.8-2.2 while free serum mg is 0.8-1.0. What is the difference between these?

Answer 25

free serum is unbound while total serum is ionized, diffusible and protein-bound mg.