Regulation of Body fluids

Question 1

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

Answer 1

2/3

Question 2

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

Answer 2

1/3

Question 3

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

Answer 3

Interstitial fluid (~75% of ECF)

Plasma volume (~25% of ECF

Question 4

What are the main cations and anions for intracellular fluid?

Answer 4

Cation: K
Anion: PO3, proteins

Question 5

What are the main cations and anions for plasma?

Answer 5

Cation: Na
Anion: Cl, CO3

Question 6

What is the equation for the anion gap?

Answer 6

Anion Gap = Na - (Cl + HCO3-)

Question 7

What are the main cations and anions for interstitial fluid?

Answer 7

Cation: Na
Anion: Cl, CO3

Question 8

What is the normal range of Na?

Answer 8

135-145

Question 9

What is the normal [Cl]?

Answer 9

104

Question 10

What is the normal range of bicarb?

Answer 10

24

Question 11

What is the normal plasma [K]?

Answer 11

~4

Question 12

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

Answer 12

Plasma

If reversed, then edema

Question 13

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

Answer 13

The presence of a lipid bilayer

Question 14

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

Answer 14

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

Question 15

What would happen if you gave a pt isotonic saline?

Answer 15

Increase in ECF volume relative to ICF

Question 16

What would happen if you gave a pt hypertonic saline?

Answer 16

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

Question 17

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

Answer 17

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

Question 18

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

Answer 18

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]

Question 19

What is an example of an effective osmole? Ineffective?

Answer 19

Effective = Na

Ineffective urea

Question 20

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

Answer 20

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

Question 21

What is thirst caused by?

Answer 21

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

Question 22

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

Answer 22

Adjusts Na balance

Question 23

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

Answer 23

1. Osmolality changes

2. Volume/pressure changes sensed via baroreceptors

Question 24

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

Answer 24

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

Question 25

How does ADH act in the pericytes of the kidneys?

Answer 25

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

Question 26

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

Answer 26

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

Question 27

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

Answer 27

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.

Question 28

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

Answer 28

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

Question 29

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

Answer 29

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

Question 30

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

Answer 30

1. Less angiotensin made 2. less aldosterone 3. Less Na reabsorption

Question 31

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

Answer 31

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

Question 32

What is the effect of NaCl on thirst?

Answer 32

Increases ECF osmolality, increasing thirst via osmoreceptors

Question 33

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

Answer 33

Increases, via decrease in atrial BP and stretch receptors