Flashcards in Regulation of Body fluids Deck (33):
ICF accounts for what percent (fraction) of total body water?
ECF accounts for what percent (fraction) of total body water?
What are the two subdivisions of ECF, and how large are they relative to total ECF?
Interstitial fluid (~75% of ECF)
Plasma volume (~25% of ECF
What are the main cations and anions for intracellular fluid?
Anion: PO3, proteins
What are the main cations and anions for plasma?
Anion: Cl, CO3
What is the equation for the anion gap?
Anion Gap = Na - (Cl + HCO3-)
What are the main cations and anions for interstitial fluid?
Anion: Cl, CO3
What is the normal range of Na?
What is the normal [Cl]?
What is the normal range of bicarb?
What is the normal plasma [K]?
Which has a higher [protein], plasma or interstitial fluid? What happens if this is reversed?
If reversed, then edema
What allows for the difference in main cations between the intracellular fluid, and the extracellular fluid?
The presence of a lipid bilayer
What happens to ECF and ICF when giving a pt pure water?
Increases volume of both ICF and ECF, lowers osmolality of both
What would happen if you gave a pt isotonic saline?
Increase in ECF volume relative to ICF
What would happen if you gave a pt hypertonic saline?
Increase in osmolality, AND increased in proportion of ECF relative to total body water
What happens to the hypothalamic osmoreceptor when it is surrounded by ECF with higher osmotic pressure?
Water leaves the cell, and the cell shrinks, causing ADH release
What is the prerequisite to have an effective osmolality sensor? Why?
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]
What is an example of an effective osmole? Ineffective?
Effective = Na
ADH is release from where, and in response to what?
From the posterior pituitary, in response to a increase in plasma osmolality/shrinkage of osmoreceptors
What is thirst caused by?
Shrinkage of the osmoreceptors in response to increased osmolality of the plasma
What is the main way that our body controls extracellular volume?
Adjusts Na balance
What are the two main ways that our bodies regulate ADH secretion? List in order of which has the greater effect.
1. Osmolality changes
2. Volume/pressure changes sensed via baroreceptors
How does ADH act in the collecting ducts of the kidneys?
Binds to vasopressin type 2 receptors on collecting ducts, causing insertion of aquaporins, and increased expression of urea transporters
How does ADH act in the pericytes of the kidneys?
Vasoconstricts the pericytes that surround the descending vasa recta and thus decreases blood flow through the vasa recta (less washing out)
What is the effect of ADH on urea uptake in the kidney? How?
increases the permeability of the medullary collecting ducts to urea by increasing the number of urea uniporters
How long is the half life of ADH (relatively)? What is the consequence of this?
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.
What happens to ECF and ICF when you have an acute increase in NaCl intake?
Action of Na+ - K+ ATPase keeps Na+ in the ECF so water leaves intracellular fluid and expands ECF.
This increases BP
Increased BP in response to increased NaCl intake leads to what? (3 sequential things)
1. Decrease in activity of renal sympathetic nerves,
2. decreasing renin production,
3. decreasing Na reabsorption
What is the effect of decreasing renin production? (3 sequential things)
1. Less angiotensin made
2. less aldosterone
3. Less Na reabsorption
What is the effect of increase NaCl on ANP? (3 sequential things)
1. Plasma volume expansion leads to
2. increase in ANP
3. Decreased renin etc.
What is the effect of NaCl on thirst?
Increases ECF osmolality, increasing thirst via osmoreceptors