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Cardiovascular, Respiratory and Renal Systems > L28 Regulation of Salt Balance > Flashcards

L28 Regulation of Salt Balance Flashcards

1
Q

What effect does excessive fluid ingestion have on ECF osmolality?

A

Excess fluid intake = ↓osmolality of ECF

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2
Q

What are some examples of events that ↑ ECF osmolality?

A

Fluid deprivation, excess solute ingestion, diarrhoea etc.

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3
Q

Which hypothalamic osmoreceptors detect ECF osmolality?

A

Supraoptic and paraventricular nuclei (regulate ADH)

Lateral preoptic (controls thirst)

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4
Q

True or false: The kidneys can produce up to 23 litres of urine per day

A

True.

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5
Q

True or false: The kidneys can produce as little as 300ml of urine per day

A

True.

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6
Q

What determines osmolality of ECF?

A) Water content
B) Salt content
C) Both A and B
D) Neither A nor B

A

C) Both A and B

Osmolality is determined not only by water content, but also by salt content

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7
Q

What is the major cation in ECF?

A

Na

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8
Q

True or false: Hypernatremia can result in hypotension

A

False.

↑Na = ↑H2O, therefore hypernatremia leads to hypertension

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9
Q

True or false hyponatremia can result in hypovolaemia

A

True.

↓Na = ↓H2O

This leads to hypovolaemia and hypotension

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10
Q

Why does water follow sodium?

A

Sodium increases osmolality of the fluid, so ↑Na in ECF will lead to ↑osmosis of water.

Water will diffuse out of a hypotonic solution into a hypertonic solution.

Hypertonic = greater osmolality = more solute

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11
Q

Increase ECF osmolality will lead to what response from the body?

A

↑ osmolality = ↑ Na

Therefore, need to increase water in ECF.

Responses: ADH secretion (↑ water retention) and thirst (↑ fluid intake)

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12
Q

Decrease ECF osmolality will lead to what response from the body?

A

↓ osmolality = ↓ Na

Therefore, ↓ water in ECF.

Responses: ADH suppression (↑ water excretion)

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13
Q

Define ‘effective circulating volume’

A

The component of blood which is perfusing the tissues

Not necessarily identical to the intravascular blood volume - e.g. congestive heart failure

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14
Q

True or false: Renin is an enzyme

A

True

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15
Q

Where is renin synthesised and stored?

A

Juxtaglomerular apparatus

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16
Q

True or false: Increasing the effective circulating volume stimulates release of renin

A

False.

↑ sympathetic activity

↓ afferent arteriolar pressure

↓ Na delivery at macula densa (end of the loop of Henle/start of distal tubule)

These are all reflective of a decrease in ECV (caused by ↓Na)

17
Q

There are two mechanism of renin release:

  1. The __1__ releases __2__, which stimulates granular cells to release renin into blood.
  2. __3__ nerves via __4__ receptors
A
  1. macula densa
  2. prostaglandin I2 (PGI2)
  3. Sympathetic
  4. beta-adrenergic
18
Q

Which agent in the RAA system is a decapeptide messenger?

A

Angiotensin I

19
Q

Which agent in the RAA system is a plasma protein that is cleaved by renin?

A

Angiotensinogen

20
Q

Which plasma endothelial enzyme converts angiotensin I to angiotensin II?

A

Angiotensin converting enzyme (ACE)

21
Q

Which agent in the RAA system is an octapeptide, and the primary hormone in Na regulation?

A

Angiotensin II

22
Q

What is angiotensin II broken down into?

A

Angiotensin III and inactive products. Broken down by plasma peptidases

23
Q

In what ways does angiotensin II increase blood pressure?

A
  1. Vasoconstriction
  2. ↑Na reabsorption from proximal tubule
  3. Stimulates aldosterone secretion - ↑Na reabsorption from distal tubule
  4. Thirst
  5. ADH release (water retention)
24
Q

Removal of which organ results in:

  1. ↑NaCl excretion via urine
  2. ↓Na in ECF
  3. ↓ ECF volume
  4. Circulatory collapse
A

Adrenal glands - loss of aldosterone

Death can be avoided by high Na diet and aldosterone replacement therapy

25
Q

Which agent in the RAA system is synthesised and secreted from zona glomerulosa?

A

Aldosterone

26
Q

Aldosterone is:

A) a glucocorticoid
B) a mineralocorticoid
C) an androgen
D) synthesised from cholesterol
E) Both B and D
A

E) Both B and D

Remember that it regulates body minerals, therefore is a mineralocorticoid.

27
Q

Which of the following is a trigger for release of aldosterone?

A) ↑ plasma [K]
B) ↓ plasma [K]
C) ↑ plasma [Na]
D) ↓ ECV
E) Both B and C
F) B, C and D
G) Both A and D
A

G) Both A and D

Stimuli for aldosterone release include:

↑ plasma K concentration
↓ plasma Na concentration
↓ ECV

28
Q

Aldosterone promotes:

A) Na reabsorption in collecting duct
B) K secretion in collecting duct
C) H secretion in collecting duct
D) Na reabsorption in gut and sweat glands
E) All of the above
A

E) All of the above

29
Q

What are principal cells and intercalated cells?

A

Cells in collecting duct epithelium.

Principal cells: main Na reabsorbing cells. Site of action for aldosterone, K-sparing diuretics and spironolactone.

Intercalated cells: H secretion, bicarbonate reabsorption

30
Q

Which 28 amino acid hormone is released in response to hypovolaemia?

A

Atrial natriuretic peptide

Atrial = released from atrial cell in response to atrial stretch

Natriuretic = causes ↑ Na excretion in urine

31
Q

Which 32 amino acid hormone is produced in the kidney and has natriuretic properties?

A

Urodilatin

Almost identical to ANP (4 extra AAs), same actions, but is produced in kidney not the atria.

32
Q

What are the actions of ANP and urodilatin?

A
  1. Inhibit collecting duct Na-K ATPase
  2. Inhibit aldosterone secretion
  3. Reduce renin secretion
  4. Promotes vasodilation of afferent arteriole to ↑ GFR (more filtrate = more Na lost)
33
Q

Which natriuretic agent is synthesised in the proximal tubule and inhibits Na-K ATPase and Na-H antiport?

A) ANP
B) BNP
C) Urodilatin
D) Dopamine
E) Kinins
F) Adrenomedullin
A

D) Dopamine

34
Q

Which 52 amino acid peptide is synthesised in the kidney, increases GFR and decreases Na tubular reabsorption?

A) ANP
B) BNP
C) Urodilatin
D) Dopamine
E) Kinins
F) Adrenomedullin
A

F) Adrenomedullin

35
Q

Which of the following counteracts ADH and is produced by the enzyme kallikrein?

A) ANP
B) BNP
C) Urodilatin
D) Dopamine
E) Kinins
F) Adrenomedullin
A

E) Kinins

Cardiovascular, Respiratory and Renal Systems (33 decks)

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