Osmotic and Volume Regulation (B2: W5) Flashcards
How do chages in volume affect ADH release?
E.g. Hemorrhage
- Plasma volume goes down, so vascular pressure drops
- Reflexes mediated by cardiovascular baroreceptors send a message
-
ADH release increases
- Plasma ADH goes up
- Tubular permeability to water goes up
- Water is reabsorbed
How does the body respond to the consumption of 1 liter of saline?
- Extracellular fluid goes up
-
ADH release goes down
- Water is excreted
- Plasma osmolarity increases
- ADH increases
Initially ADH goes down, but eventually is increased again
How does the body respond to the consumption of 1 liter of distilled water?
- Plasma osmolarity decreases
- ADH is decreased
- Want to raise Posm
- Water is excreted
How is extracellular fluid volume regulated?
By regulating sodium reabsorption
Where is sodium reabsorbed along the neprhon?
- 67% reabsorbed in the proximal tubule
- More is reabsorbed in the ascending limb
- 8% remaining
- Additional reabsorption in distal tubule, convoluted collecting tubule, and collecting duct
- 0.5% is usually excreted
When juxtaglomerular cells sense less stretch, they release ______.
Renin
What factors are associated with moving sodium back into the body to control extracellular fluid volume?
Kidney is in control of sodium retention
Affected by
- GFR
- Aldosterone
- Natriuretic hormone
- Peritubular pressure
When regulating volume, which is regulated first: sodium or water?
Regulation of volume requires first regulating sodium followed by regulating water
What is the relationship between filtered load and sodium reabsorption in the proximal tubule?
As the filtered load of Na goes up, a constant proporiton is reabsorbed in the proximal tubule - 67%
- In the case of hypovolemia
- Shifts graph to be more efficient and save salt
- Slope goes up - maybe 69% instead
- In the case of hypervolemia
- Slope goes down and less salt is saved
Why does excess sodium consumption lead to an increase in extracellular fluid volume?
- Plasma [Na] goes up
- Plasma osmolarity increases
- Shifts water from inside of cells OUT
- Increase ADH to save water
- Water reabsorption and consumption
- Extracellular volume increases again
This process is slower than just drinking water
How does aldosterone affect collecting duct principal cells?
- Aldosterone released in response to BP decrease (Angiotensin II) or in response to hyperkalemia
- Aldosterone gets into cell to intracellular receptor where it affects the synthesis of proteins
- Makes more Na channels
- Enhances ATP generation
- Makes more Na/K ATPases
How does aldosterone affect hydrogen atoms?
Enhances H+ secretion in the collecting duct
- Becomes more acidic
- More Na is reabsorbed back into the body
What are the two primary regulators of aldosterone release?
- Increased angiotensin II
- Increased plasma potassium concentration
Two minor regulators that are not as important
What three effects does aldosterone have on the kidneys?
- Increased Na reabsorption
- Increased K excretion
- Increased H excretion
What are the effects of hypoaldosteronemia (e.g. adrenal insufficiency - Addison’s disease)?
- Acidosis
- Hyperkalemia
- Hypotensin (salt wasting)