Electrolytes in body fluids

Question 1

What are the seven essential electrolytes?

Answer 1

Ions of:
1. Sodium (Na⁺)
2. Chloride (Cl⁻)
3. Potassium (K⁺)
4. Bicarbonate (HCO₃⁻)
5. Calcium (Ca²⁺)
6. Phosphate (HPO₄²⁻)
7. Magnesium (Mg²⁺)

Question 2

Are electrolytes usually confined to particular fluid compartments?

Answer 2

Yes

Question 3

What are the four general functions of electrolytes?

Answer 3

1. Control the osmosis of water between fluid compartments
2. Help maintain acid-base balance
3. Carry electrical current
4. Serve as cofactors

Question 4

Which three electrolytes are generally confined to ECF?

Answer 4

1. Sodium, Na⁺
2. Chloride, Cl⁻
3. Calcium, Ca²⁺

Question 5

Which three electrolytes are generally confined to ICF?

Answer 5

1. Potassium, K⁺
2. Magnesium, Mg²⁺
3. Phosphate, HPO₄²⁻

Question 6

What are the two primary functions of sodium ions (Na⁺)?

Answer 6

1. Maintaining fluid and electrolyte balance
2. Generation and conduction of action potentials in neurons and muscle fibres

Question 7

Which three hormones control the Na⁺ level in blood?

Answer 7

1. Aldosterone
2. Antidiuretic hormone (ADH)
3. Atrial natriuretic peptide (ANP)

Question 8

What is the action of aldosterone in Na⁺ regulation?

Answer 8

Increases Na⁺ levels and blood volume by increasing renal Na⁺ and water reabsorption

Question 9

What is the action of antidiuretic hormone (ADH) in Na⁺ regulation?

Answer 9

Increases Na⁺ concentration via reduced levels of ADH allowing greater excretion of water in urine

Question 10

What is the action of atrial natriuretic peptide in Na⁺ regulation?

Answer 10

Reduces Na⁺ levels by increasing Na⁺ excretion and urine output by the kidneys

Question 11

What are the three primary functions of chloride ions (Cl⁻)?

Answer 11

1. Helps balance the level of anions in different fluid compartments
2. Supports fluid balance between compartments
3. Are part of hydrochloric acid secreted in to gastric juice

Question 12

How is Cl⁻ balance in body fluids regulated?

Answer 12

By any processes that increase or decrease renal reabsorption of Na⁺ (they typically move in unison), and ADH (affects Cl concentration too)

Question 13

What are the three main functions of potassium ions (K⁺)?

Answer 13

1. Establishing resting membrane potential and repolarisation phase of action potentials
2. Helps maintain normal ICF volume
3. Helps regulate pH of body fluids (by swapping places with H⁺)

Question 14

What is the main hormone which controls K⁺ levels?

Answer 14

Aldosterone, by encouraging excretion of K⁺ in the urine when concentration is high

Question 15

How can abnormal K⁺ levels be fatal?

Answer 15

It is needed for the depolarisation phase of nerve impulses
Example effect: ventricular fibrillation

Question 16

What are the two primary functions of bicarbonate ions (HCO₃⁻)?

Answer 16

1. Helps maintain correct balance of anions in ECF by exchanging places with Cl⁻
2. Acts as a weak acid in buffer systems to maintain acid-base balance

Question 17

What two processes cause blood concentration of HCO₃⁻ to decrease?

Answer 17

1. Exhalation of CO₂ by the lungs
2. Excretion of excess by the kidneys

Question 18

What two processes cause blood concentration of HCO₃⁻ to increase?

Answer 18

1. The release of CO₂ in to the blood by metabolically active cells (CO₂ + H₂O > H₂CO₃ > H⁺ + HCO₃⁻)
2. Formation in the kidneys if levels are too low

Question 19

What are the four main functions of calcium ions (Ca²⁺)?

Answer 19

Roles in:
1. Blood clotting
2. Neurotransmitter release
3. Maintenance of muscle tone
4. Excitability of nervous and muscle tissue

Question 20

Which hormone is the most important regulator of Ca²⁺ concentration in blood plasma?

Answer 20

Parathyroid hormone (PTH)

Question 21

What are the three ways PTH affects Ca²⁺ concentration of the blood plasma?

Answer 21

1. Stimulates osteoclasts to release calcium (bone resorption)
2. Enhances reabsorption of Ca²⁺ by the kidneys
3. Increases production of calcitriol (a form of vitamin D) which increases Ca²⁺ absorption from food

Question 22

How does the body reduce Ca²⁺ concentration in the blood plasma, if needed?

Answer 22

Release of calcitonin (produced in the thyroid gland) which inhibits osteoclasts and accelerates Ca²⁺ deposition into bones

Question 23

What are the three types of phosphate ions, and which is the most prevalent?

Answer 23

1. HPO₄²⁻ (most prevalent)
2. H₂PO₄⁻
3. PO₄³⁻

Question 24

What are the two main functions of phosphate ions?

Answer 24

1. Most are covalently bonded to organic molecules e.g. phospholipids, ATP, nucleic acids
2. Act as a buffer in acid-base balance

Question 25

What are the main two hormones which regulate blood HPO₄²⁻ levels?

Answer 25

1. Parathyroid hormone 2. Calcitriol

Question 26

How does PTH affect blood HPO₄²⁻ levels?

Answer 26

1. Stimulates bone resorption to increase blood levels 2. Inhibits resorption of HPO₄²⁻ by the kidneys to decrease blood levels

Question 27

How does calcitriol affect HPO₄²⁻ levels?

Answer 27

Promotes absorption of phosphates in the digestive canal to increase blood levels

Question 28

What other 'local hormone' (a polypeptide paracrine) also helps regulate HPO₄²⁻?

Answer 28

Fibroblast growth factor 23 (FGF 23)

Question 29

How does FGF 23 affect HPO₄²⁻ levels and by what two methods?

Answer 29

Decreases blood levels by: 1. Increasing HPO₄²⁻ excretion by the kidneys 2. Decreasing absorption of HPO₄²⁻ by the digestive canal

Question 30

What are the three main functions of magnesium ions (Mg²⁺)?

Answer 30

1. Cofactor for the sodium-potassium pump and certain enzymes in carbohydrate and protein metabolism 2. Neuromuscular activity, synaptic transmission and myocardial functioning 3. Secretion of parathyroid hormone (PTH)

Question 31

In what five body states will Mg²⁺ excretion by the kidneys increase?

Answer 31

1. Hypercalcaemia 2. Hypermagnasemia 3. Increases in ECF volume 4. Decreases in PTH 5. Acidosis

Question 32

In what five body states will Mg²⁺ excretion by the kidneys decrease?

Answer 32

1. Hypocalcaemia 2. Hypomagnasemia 3. Decreases in ECF volume 4. Increases in PTH 5. Alkalosis

Question 33

Which two pairs of electrolytes regularly swap places to support acid-base/pH balance?

Answer 33

1. K⁺ with H⁺ to support acid base balance 2. Cl⁻ with HCO₃⁻ via antiporters between blood cells (ICF) and blood plasma (ECF)

Question 34

Which five medical interventions can increase risk of electrolyte imbalances?

Answer 34

1. IV infusions 2. Drainages or suctions 3. Urinary catheters 4. Diuretics 5. Fluid restrictions

Question 35

Which four population groups have increased risk of electrolyte imbalances?

Answer 35

1. Dependent individuals e.g. infants, the elderly, people with altered levels of consciousness or impaired communication 2. Athletes and military personnel in extremely hot environments 3. Post-operative individuals 4. People with severe burns or trauma

Question 36

In which four long-term conditions are electrolyte imbalances more likely?

Answer 36

1. Congestive heart failure 2. Diabetes 3. COPD 4. Cancer

Question 37

What are the names for deficiency and excess of Na⁺, respectively?

Answer 37

Hyponatraemia and hypernatraemia

Question 38

What are the names for deficiency and excess of Cl⁻, respectively?

Answer 38

Hypochloraemia and hyperchloraemia

Question 39

What are the names for deficiency and excess of K⁺, respectively?

Answer 39

Hypokalaemia and hyperkalaemia

Question 40

What are the names for deficiency and excess of Ca²⁺, respectively?

Answer 40

Hypocalcaemia and hypercalcaemia

Question 41

What are the names for deficiency and excess of HPO₄²⁻, respectively?

Answer 41

Hypophosphataemia and hyperphosphataemia

Question 42

What are the names for deficiency and excess of Mg²⁺, respectively?

Answer 42

Hypomagnesaemia and hypermagnasaemia

Question 43

What are the signs and symptoms of hypernatraemia?

Answer 43

1. Intense thirst 2. Hypertension 3. Oedema 4. Agitation and convulsions

Question 44

What are the signs and symptoms of hyponatraemia?

Answer 44

1. Muscular weakness 2. Dizziness, headache, confusion, stupor and coma 3. Hypotension 4. Tachycardia and shock

Question 45

What are some general signs of electrolyte deficiency?

Answer 45

1. Tingling 2. Spasms and cramps 3. Mental confusion 4. Muscular weakness

Question 46

What are some general signs of electrolyte excess?

Answer 46

1. Nausea and vomiting 2. Anorexia 3. Muscular weakness 4. Lethargy