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Fluid, electrolyte and acid-base homeostasis > Electrolytes in body fluids > Flashcards

Electrolytes in body fluids Flashcards

Compare the electrolyte composition of blood plasma, interstitial fluid and ICF; discuss the functions and regulation of the 7 electrolytes

1
Q

What are the seven essential electrolytes?

A

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

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2
Q

Are electrolytes usually confined to particular fluid compartments?

A

Yes

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3
Q

What are the four general functions of electrolytes?

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

Which three electrolytes are generally confined to ECF?

A
  1. Sodium, Na⁺
  2. Chloride, Cl⁻
  3. Calcium, Ca²⁺
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5
Q

Which three electrolytes are generally confined to ICF?

A
  1. Potassium, K⁺
  2. Magnesium, Mg²⁺
  3. Phosphate, HPO₄²⁻
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6
Q

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

A
  1. Maintaining fluid and electrolyte balance
  2. Generation and conduction of action potentials in neurons and muscle fibres
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7
Q

Which three hormones control the Na⁺ level in blood?

A
  1. Aldosterone
  2. Antidiuretic hormone (ADH)
  3. Atrial natriuretic peptide (ANP)
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8
Q

What is the action of aldosterone in Na⁺ regulation?

A

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

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9
Q

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

A

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

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10
Q

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

A

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

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11
Q

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

A
  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
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12
Q

How is Cl⁻ balance in body fluids regulated?

A

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

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13
Q

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

A
  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⁺)
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14
Q

What is the main hormone which controls K⁺ levels?

A

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

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15
Q

How can abnormal K⁺ levels be fatal?

A

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

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16
Q

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

A
  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
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17
Q

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

A
  1. Exhalation of CO₂ by the lungs
  2. Excretion of excess by the kidneys
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18
Q

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

A
  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
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19
Q

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

A

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

20
Q

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

A

Parathyroid hormone (PTH)

21
Q

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

A
  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
22
Q

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

A

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

23
Q

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

A
  1. HPO₄²⁻ (most prevalent)
  2. H₂PO₄⁻
  3. PO₄³⁻
24
Q

What are the two main functions of phosphate ions?

A
  1. Most are covalently bonded to organic molecules e.g. phospholipids, ATP, nucleic acids
  2. Act as a buffer in acid-base balance
25
Q

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

A
  1. Parathyroid hormone
  2. Calcitriol
26
Q

How does PTH affect blood HPO₄²⁻ levels?

A
  1. Stimulates bone resorption to increase blood levels
  2. Inhibits resorption of HPO₄²⁻ by the kidneys to decrease blood levels
27
Q

How does calcitriol affect HPO₄²⁻ levels?

A

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

28
Q

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

A

Fibroblast growth factor 23 (FGF 23)

29
Q

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

A

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

30
Q

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

A
  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)
31
Q

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

A
  1. Hypercalcaemia
  2. Hypermagnasemia
  3. Increases in ECF volume
  4. Decreases in PTH
  5. Acidosis
32
Q

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

A
  1. Hypocalcaemia
  2. Hypomagnasemia
  3. Decreases in ECF volume
  4. Increases in PTH
  5. Alkalosis
33
Q

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

A
  1. K⁺ with H⁺ to support acid base balance
  2. Cl⁻ with HCO₃⁻ via antiporters between blood cells (ICF) and blood plasma (ECF)
34
Q

Which five medical interventions can increase risk of electrolyte imbalances?

A
  1. IV infusions
  2. Drainages or suctions
  3. Urinary catheters
  4. Diuretics
  5. Fluid restrictions
35
Q

Which four population groups have increased risk of electrolyte imbalances?

A
  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
36
Q

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

A
  1. Congestive heart failure
  2. Diabetes
  3. COPD
  4. Cancer
37
Q

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

A

Hyponatraemia and hypernatraemia

38
Q

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

A

Hypochloraemia and hyperchloraemia

39
Q

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

A

Hypokalaemia and hyperkalaemia

40
Q

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

A

Hypocalcaemia and hypercalcaemia

41
Q

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

A

Hypophosphataemia and hyperphosphataemia

42
Q

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

A

Hypomagnesaemia and hypermagnasaemia

43
Q

What are the signs and symptoms of hypernatraemia?

A
  1. Intense thirst
  2. Hypertension
  3. Oedema
  4. Agitation and convulsions
44
Q

What are the signs and symptoms of hyponatraemia?

A
  1. Muscular weakness
  2. Dizziness, headache, confusion, stupor and coma
  3. Hypotension
  4. Tachycardia and shock
45
Q

What are some general signs of electrolyte deficiency?

A
  1. Tingling
  2. Spasms and cramps
  3. Mental confusion
  4. Muscular weakness
46
Q

What are some general signs of electrolyte excess?

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

Fluid, electrolyte and acid-base homeostasis (2 decks)

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