Regulation of Body fluids Flashcards

1
Q

ICF accounts for what percent (fraction) of total body water?

A

2/3

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2
Q

ECF accounts for what percent (fraction) of total body water?

A

1/3

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3
Q

What are the two subdivisions of ECF, and how large are they relative to total ECF?

A

Interstitial fluid (~75% of ECF)

Plasma volume (~25% of ECF

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4
Q

What are the main cations and anions for intracellular fluid?

A

Cation: K
Anion: PO3, proteins

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5
Q

What are the main cations and anions for plasma?

A

Cation: Na
Anion: Cl, CO3

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6
Q

What is the equation for the anion gap?

A

Anion Gap = Na - (Cl + HCO3-)

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7
Q

What are the main cations and anions for interstitial fluid?

A

Cation: Na
Anion: Cl, CO3

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8
Q

What is the normal range of Na?

A

135-145

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9
Q

What is the normal [Cl]?

A

104

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10
Q

What is the normal range of bicarb?

A

24

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11
Q

What is the normal plasma [K]?

A

~4

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12
Q

Which has a higher [protein], plasma or interstitial fluid? What happens if this is reversed?

A

Plasma

If reversed, then edema

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13
Q

What allows for the difference in main cations between the intracellular fluid, and the extracellular fluid?

A

The presence of a lipid bilayer

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14
Q

What happens to ECF and ICF when giving a pt pure water?

A

Increases volume of both ICF and ECF, lowers osmolality of both

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15
Q

What would happen if you gave a pt isotonic saline?

A

Increase in ECF volume relative to ICF

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16
Q

What would happen if you gave a pt hypertonic saline?

A

Increase in osmolality, AND increased in proportion of ECF relative to total body water

17
Q

What happens to the hypothalamic osmoreceptor when it is surrounded by ECF with higher osmotic pressure?

A

Water leaves the cell, and the cell shrinks, causing ADH release

18
Q

What is the prerequisite to have an effective osmolality sensor? Why?

A

A lipid membrane the is more permeable to water than to a solute. Otherwise the ion would just follow the water, and not change [water]

19
Q

What is an example of an effective osmole? Ineffective?

A

Effective = Na

Ineffective urea

20
Q

ADH is release from where, and in response to what?

A

From the posterior pituitary, in response to a increase in plasma osmolality/shrinkage of osmoreceptors

21
Q

What is thirst caused by?

A

Shrinkage of the osmoreceptors in response to increased osmolality of the plasma

22
Q

What is the main way that our body controls extracellular volume?

A

Adjusts Na balance

23
Q

What are the two main ways that our bodies regulate ADH secretion? List in order of which has the greater effect.

A
  1. Osmolality changes

2. Volume/pressure changes sensed via baroreceptors

24
Q

How does ADH act in the collecting ducts of the kidneys?

A

Binds to vasopressin type 2 receptors on collecting ducts, causing insertion of aquaporins, and increased expression of urea transporters

25
Q

How does ADH act in the pericytes of the kidneys?

A

Vasoconstricts the pericytes that surround the descending vasa recta and thus decreases blood flow through the vasa recta (less washing out)

26
Q

What is the effect of ADH on urea uptake in the kidney? How?

A

increases the permeability of the medullary collecting ducts to urea by increasing the number of urea uniporters

27
Q

How long is the half life of ADH (relatively)? What is the consequence of this?

A

short half-life (only a few minutes) so prolonged stimulation of increased water permeability in the collecting ducts requires continuous stimulation of the ADH-secreting hormones.

28
Q

What happens to ECF and ICF when you have an acute increase in NaCl intake?

A

Action of Na+ - K+ ATPase keeps Na+ in the ECF so water leaves intracellular fluid and expands ECF.

This increases BP

29
Q

Increased BP in response to increased NaCl intake leads to what? (3 sequential things)

A
  1. Decrease in activity of renal sympathetic nerves,
  2. decreasing renin production,
  3. decreasing Na reabsorption
30
Q

What is the effect of decreasing renin production? (3 sequential things)

A
  1. Less angiotensin made
  2. less aldosterone
  3. Less Na reabsorption
31
Q

What is the effect of increase NaCl on ANP? (3 sequential things)

A
  1. Plasma volume expansion leads to
  2. increase in ANP
  3. Decreased renin etc.
32
Q

What is the effect of NaCl on thirst?

A

Increases ECF osmolality, increasing thirst via osmoreceptors

33
Q

What is the effect of a hemorrhage on renin secretion? How?

A

Increases, via decrease in atrial BP and stretch receptors