Regulation of Osmolarity Flashcards
What is water controlled by ?
ADH
How does plasma osmolarity affect ADH?
Increased plasma osmolarity causes an increased rate of ADH secreting hormones. and then ADH increases
Where are osmoreceptors found?
The anterior hypothalamus
What occurs when the volume of osmoreceptors changes?
There is a change in osmoreceptor discharge
What is the rate of normal plasma osmolality?
280-290mOsm/kg H2O
What occurs when you increase NaCl concentration?
There is a decrease in plasma volume, an increase in discharge and an increase in ADH
Why is osmolarity uneffective without tonicity?
No osmotic drag is created without tonicity
The amount of urine produces is dependent on what?
ADH concentration and the amount of solute to be excreted
What does the ingestion of hypertonic solition do to the body?
Increases urine flow which induces dehydration
Where is the site of water regulation?
The collecting duct
What occurs when vasopressin binds to the membrane receptor?
cAMP is activated and cells insert AQP2 water pores into the apical membrane. Water is then absorbed by osmosis into the blood
When is [ADH] at a maximum level?
During a water deficit. It effectively adds pure H2O into the ECF
Describe the oncotic pressure level of the vasa recta during a water deficit?
It is increased
What happens when ADH is absent?
Collecting ducts are impermeable to h20 so a large volume of dilute urine is excreted, compensating for H2O excess
Why is urea retained during anti-diuresis?
To save water and reinforce medullary gradient in region of thin ascending limb of LoH
