DSA 2

Question 1

Normal ranges of plasma: K+, Ca2+, PO4, Mg2+

Answer 1

1. 3.5-5mEq/L
2. 1000mg/day
3. 1500mg
4. 1.8 mEq/L

Question 2

Where is K+ distributed throughout the body?

Answer 2

98% ICF, 2% ECF

*of the ICF, 80% muscle cells, 20% other cells

Question 3

What causes the difference between K+ ICF and ECF levels?

Answer 3

Na/K ATPase, NKCC2, K+ channels, Transcellular distribution regulated by other factors

Question 4

Hypokalemia

Answer 4

1. Plasma [K+] < 3.7
2. Vomiting/diarrhea, insulin excess, deficiency, alkalosis
3. Hyperpolarizes the membrane, and cell is less excitable

Question 5

Hyperkalemia

Answer 5

1. Plasma [K+] >5.2
2. Excess intake, tissue release (rhabdomyolysis, burns, hemolysis), shifts ICF–>ECF (acidosis, insulin deficiency, tissue damage, hyperglycemia)
3. Hypopolarizes the membrane, and cell is more excitable

Question 6

Pseudohyperkalemia

Answer 6

1. artificially high Plasma [K+]

2. RBC lysis during blood daw

Question 7

How is K+ excreted from the body?

Answer 7

1. Feces (10)
2. Kidneys (60)

*assuming 70 intake via GI

Question 8

How do cardiac cells respond to hyperkalemia? hypokalemia?

Answer 8

1. hyper polarizes membrane–>less excitable (brady)
   a. tall, peaked T wave
2. hypo polarizes membrane–>more excitable (tachy)
   a. low T wave

Question 9

Cell Volume Maintenance:

a. Net loss of K+
b. Net gain of K+

Answer 9

a. cell shrinkage

b. cell swellings

Question 10

Intracellular pH regulation:

a. Low plasma [K+]
b. High plasma [K+]

Answer 10

a. cell acidosis

b. cell alkalosis

Question 11

DNA/protein synthesis, growth:

a. Lack of K+

Answer 11

a. reduction of protein synthesis, stunted growth

Question 12

RMP:

a. Reduced [K+]i/[K+]o
b. Increased [K+]i/[K+]o

Answer 12

a. membrane depolarization

b. membrane hyperpolarization

Question 13

Neuromuscular activity:

a. Low plasma [K+]
b. High plasma [K+]

Answer 13

a. muscle weakness, muscle paralysis, intestinal distention, respiratory failure
b. initially increased muscle excitability; later–>muscle weakness (paralysis)

Question 14

Cardiac activity:

a. Low plasma [K+]
b. High plasma [K+]

Answer 14

a. prolonged repolarization; slowed conduction; abnormal pacemaker activity–>tachyarrhythmias
b. enhanced repolarization; slowed conduction–> bradyarrhythmias and cardiac arrest

Question 15

Vascular resistance:

a. Low plasma [K+]
b. High plasma [K+]

Answer 15

a. vasoconstriction

b. vasodilation

Question 16

How does insulin affect K+ distribution?

Answer 16

enhanced cell uptake

Question 17

How does beta-catecholamines affect K+ distribution? alpha-catecholamines?

Answer 17

a. enhanced cell uptake

b. impaired cell uptake

Question 18

How does acidosis affect K+ distribution? alkalosis

Answer 18

a. impaired cell uptake

b. enhanced cell uptake

Question 19

How does external K+ balance affect K+ distribution?

Answer 19

loose correlation

Question 20

How does cell damage affect K+ distribution? hyperosmolality?

Answer 20

a. impaired cell uptake

b. enhanced cell efflux

Question 21

3 ways Ca2+ can enter circulation

Answer 21

1. Reabsorption from the kidneys
2. Resorption from bones
3. Ingestion

Question 22

What does hypocalcemia cause? hypercalcemia?

Answer 22

1. Increases neuromuscular excitability (tetany/spasticity)
2. Depress neuromuscular excitability (threshold shifts away from RMP)

*Regulators: PTH, calcitonin, caclitriol

Question 23

What can cause elevated serum Ca2+? Low levels?

Answer 23

1. Primary hyperparathyroidism, malignancy

2. Hypoparathyroidism, renal disease, vitamin D deficiency

Question 24

Where is phosphate distributed throughout the body?

Answer 24

a. bone - 85%
b. cells - 14%
c. serum - 1%

*lost through stool, urine, or distribution into bone

Question 25

What are the roles of the following phosphate metabolism regulators: dietary? calcitriol? PTH? Renal tubular reabsorption?

Answer 25

1. intake/absorption
2. increases phosphorous resorption from bone and absorption from intestine
3. phosphorous respiration directly from bone, and indirectly activates intestinal absorption through stimulation of calcitriol production
4. stimulated by tubular filtered load of phosphorous and inhibited by PTH

Question 26

Where is Mg2+ distributed throughout the body?

Answer 26

a. bone - 50%
b. ICF (muscle) - 49%
c. ECF - 1%

*depletion is associated with migraine, depression, epilepsy, SIDS, arrhythmia, preeclampsia, muscle cramps