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Digestion and Excretion > Extracellular fluid volume and sodium balance > Flashcards

Extracellular fluid volume and sodium balance Flashcards

1
Q

How is ECF volume regulated?

A

Regulation of body sodium content which is a vital function of kidneys

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2
Q

What is the effective circulating volume (ECV)?

A

Component of ECF which is perfusing tissues

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3
Q

What is ECV monitored by?

A

Low pressure baroreceptors
High pressure baroreceptors
CNS
Hepatic nervous system

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4
Q

What is ECV control dependent on?

A

Sodium balance

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5
Q

How is Na+ balance regulated?

A

Action of renal nerves
RAAS
Natriuretic peptides

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6
Q

What does the activation of the RAAS system result in?

A

Increase in blood pressure
decrease in salt and water excretion by the kidneys

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7
Q

What does severe haemorrhage cause?

A

Decreased renal perfusion -> elevated levels of renin in the blood

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8
Q

Where is renin synthesized and stored?

A

Granular cells

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9
Q

What is the stimulus for renin synthesis?

A

Wall tension - pulse pressure

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10
Q

What are granular cells?

A

Pressure sensitive cells

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11
Q

What does volume contraction cause?

A

increases renal sympathetic nerve activity

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12
Q

How do neural signals from vasomotor centre reach granular cells?

A

Renal sympathetic nerves

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13
Q

What do granular cells express?

A

Beta 1 adrenergic receptors

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14
Q

What stimulates these receptors?

A

Epinephrine or norephrine

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15
Q

What happens when beta 1 receptors are stimulated?

A

Induce renin secretion

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16
Q

What are the salt sensing cells in the JGA?

A

Macula densa cells

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17
Q

What does decreased renal perfusion cause?

A

Lower GFR and decreased filtered load of NaCl

18
Q

What does decreased NaCl delivery cause?

A

Increased renin release

19
Q

Are Ca2+ levels increased or decreased in granular cells during these mechanisms?

A

Decreased

20
Q

What does elevated plasma levels result in?

A

Elevated angiotensin II levels

21
Q

What does ANG2 produce?

A

Systemic vasoconstriction which increases TPR and increased BP

22
Q

What does ANG2 stimulate?

A

The adrenal cortex to produce aldosterone

23
Q

What does aldosterone stimulate?

A

Na+ reabsorption and K+ secretion from distal nephron

24
Q

What diuretic drug blocks aldosterone?

A

Spironolactone

25
Q

What does aldosterone bind to in principal cells?

A

Mineral corticoid receptors

26
Q

What does aldosterone binding cause?

A

Conformational change that reveals nuclear localization signal

27
Q

What does the nucleus promote after aldosterone binding?

A

Gene expression and synthesis of:
- NA+/K+ATPase pumps and K+ channels in BM
- ENaC channels and K+ channels in AM
- SGK1 which increases ENaC in AM and K+ channels

28
Q

What happens when maximal concentration of aldosterone is reached?

A

Virtually no sodium excreted

29
Q

What other factors increase aldosterone release?

A

Small increase in plasma K+
Decrease in plasma Na+

30
Q

What are 5 other functions of ANG2?

A

Stimulates NaCl absorption in PCT
Vasoconstricts renal arterioles
Constricts mesangial cells
Increases thirst by acting on hypothalamus
Increases ADH secretion

31
Q

Where is angiotensin mainly produced?

A

Liver

32
Q

Where is ACE expressed?

A

Luminal surface of endothelial cells (particularly the lungs)

33
Q

What blocks ANG?

A

ACE inhibitors and ANG2 receptor blockers

34
Q

What is plasma concentration of ANG2 dependent on?

A

Plasma concentration of renin

35
Q

What does increased atrial natriuretic peptide (ANP) levels cause?

A

Increased Na+ excretion

36
Q

What do cardiac stretch receptors monitor?

A

Central volume

37
Q

When are natriuretic peptides released?

A

When cardiac stretch receptors are distended

38
Q

What do atrial myocytes release?

A

ANP

39
Q

What do ventricular myocytes release?

A

BNP (brain)

40
Q

What do NPs antagonize?

A

RAAS system

41
Q

What 5 things do NPs cause?

A

Vasodilation of afferent and vasoconstriction of efferent arterioles
Inhibition of renin secretion
Inhibition of aldosterone secretion
Inhibition of NaCl reabsorption in CD
Inhibition of ADH secretion

Digestion and Excretion (22 decks)

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