Control of Plasma Osmolarity Flashcards
What is the osmolarity of most body fluids and what is the exception to this?
300 mOsm/Kg , urine can vary a lot
If our water intake is greater than what we excrete, will the plasma osmolarity be high or low?
Low
The balance of what substance changes plasma osmolarity?
Water
What type of nephron is responsible for making concentrated urine?
Juxtamedullary nephrons
What is the medullary counter current mechanism?
The flow of filtrate in the loop of henle and blood in the vasta recta, flow in opposite directions to maintain a gradient of concentration
What is the most concentrated urine can get?
1200 mOsm/Kg
In what patients is a concentration gradient in the kidney not seen?
Transplant patients and patients on prolonged loop diuretics. Osmolarity is the same throughout at 300 mOsm/Kg
Roughly how much filtered urea is reabsorbed?
1/2
What hormone and channel causes urea re-cycling?
ADH and aquaporin channels, urea is removed from the collecting duct
Why do we have a slow flow of blood through the renal medulla?
To prevent washing out the concentration gradient with a high flow of blood
What is the vasa recta?
A capillary bed of straight vessels found only in JM nephrons
Where are osmoreceptors located?
Hypothalamus, specifically OVLT
What do osmoreceptors do?
sense changes in plasma osmolarity and regulate ADH release and thirst
What happens to control of plasma osmolarity when there is a large loss of volume?
The set point for osmolarity can shift as maintaining volume is much more important.
Name 2 conditions that can occur with too little ADH
Central Diabetes insipidus and Nephrogenic diabetes insipidus
