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The Endocrine System > Sodium and Water Balance > Flashcards

Sodium and Water Balance Flashcards

1
Q

How is serum sodium concentration measured?

A

[Na+] = mmol Na+/1L H2O

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2
Q

What is the reference interval for serum sodium concentration?

A

135-145mmol/l

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3
Q

Generally, hyponatraemia becauses more serious when sodium levels fall below what level?

A

<120 mmol/l

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4
Q

A low serum sodium concentration can be caused by which two things?

A
  1. Low sodium concentration
  2. High water concentration
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5
Q

What symptoms may be experienced with hyponatraemia?

A
  1. Altered conciousness
  2. Confusion
  3. Nausea
  4. Vomiting
  5. Fitting
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6
Q

In which two compartments is water present within the body?

A
  1. Extracellular fluid (ECF)
  2. Intracellular fluid (ICF)
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7
Q

The _____cellular fluid volume is much greater than the _____cellular fluid volume

A

The intracellular fluid volume is much greater than the extracellular fluid volume

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8
Q

Which fluid compartment contains the vast majority of sodium?

A

ECF

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9
Q

Why is it that the ECF has a far higher sodium content?

A

Na+/K+ pump activity

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10
Q

Why is it possible to gain or lose a lot of water without suffering from clinical signs?

A

Gain or loss is spread across a large volume (ICF + ECF)

Effects are therefore “diluted”

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11
Q

Loss of sodium will lead to a loss of what?

A

Water

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12
Q

How is it possible for the kidneys to regulate water volume in the body?

A

By either retaining or excreting sodium, water is conserved or lost respectively

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13
Q

How does a low sodium concentration impact the intracellular fluid?

A

It doesn’t

The ECF is reduced but the ICF remains relatively constant

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14
Q

How does an increased H2O concentration impact the ECF and ICF?

A

They both increase

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15
Q

How is dehydration and hyponatraemia treated?

A

Administer sodium

  1. IV saline in an emergency
  2. Oral sodium can also be used
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16
Q

How is oedema and hyponatraemia treated?

A

Fluid restriction

17
Q

The RAAS pathway acts to _________ blood pressure

A

The RAAS pathway acts to increase blood pressure

18
Q

Which two key endogenous steroids have mineralocorticoid activity?

A
  1. Aldosterone
  2. Cortisol
19
Q

Increased mineralocorticoid activity leads to what?

A
  1. Sodium retention
  2. Increased blood pressure
20
Q

Where does ADH act and what is the result of its action?

A

Renal tubules

Water reabsorption

21
Q

What is the name given to the concentrating mechanism within the kidneys which occurs as a result of ADH?

A

Countercurrent multiplication

22
Q

What properties of the descending limb of Henle allow for countercurrent multiplication?

A
  1. Highly permeable to water
  2. Impermeable to NaCl
23
Q

What properties of the ascending limb of Henle allow for countercurrent multiplication?

A
  1. Active excrusion of NaCl into ECF
  2. Impermeable to water
24
Q

How is water lost from the descending limb of Henle?

A

In response to NaCl being pumped into the interstitial fluid from the ascending limb of Henle

25
Q

Sodium is pumped out from the ascending limb of Henle until what osmolar difference exists between the ascending limb of Henle and descending limb of Henle/interstitial fluid?

A

200mos/litre

26
Q

Countercurrent multiplication continues until he fluid in the descending limb of Henle reaches a maximally hypertonic value of what?

A

1200mos/litre

27
Q

Name 3 non-osmotic stimuli for ADH release?

A
  1. Hypovolaemia/hypotension
  2. Pain
  3. Nausea and vomiting
28
Q

What are some pathological reasons for an increased sodium loss?

A
  1. Adrenal/kidney causes
  2. Poor absorption in gut
  3. Skin (e.g. burns)
29
Q

What are some pathological reasons for an increased water concentration?

A
  1. Decreased excretion (e.g. SIADH)
  2. Increased intake (compulsive water drinking)
30
Q

Sodium levels may be considered very high at which level?

A

>160mmol/L

31
Q

How does an increased sodium concentration impact the ICF?

A

It doesn’t

It only affects (increases) the ECF

32
Q

For which pathological reasons may there be increased water loss and subsequent rise is sodium levels?

A
  1. H2O loss e.g. DI
  2. Decreased H2O intake
33
Q

In which situation is increased sodium most common?

A

Diabetic ketoacidosis

(especially when associated with vomiting)

34
Q

How is hypernatraemia treated in the even of little water?

A

Give water

35
Q

How is hypernatraemia treated in the event of too much sodium?

A

Loop diuretic

36
Q

Why does Addison’s disease lead to hyponatraemia?

A

Adrenal insufficiency

Not enough steroids are made and sodium cannot be retained

Sodium and water are lost

37
Q

Why are loop diuretics used to treat patients with oedema?

A

There is excess water and sodium

Loop diuretics cause loss of both

The Endocrine System (35 decks)

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