Water Balance Flashcards
What determines ECF volume
Level of salt
What is used to regulate plasma osmolarity
water balance
How do we get rid of water?
Skin and sweat
Faeces
Respiration
Urine output - controllable
How to concentrate urine above normal plasma osmolarity?
Produce a region of hyperosmolar instersitial fluid
What are the 3 urea transporters?
UT-A1/3 KO
UT-A2 KO
UT-B KO
What happens if the UT-A1/3 KO transporter is faulty?
Reduced urea int he inner medulla
Severe reduction in ability to concentrate urine
Increased water intake by 20%
No ability to reduce urine output if water restricted for 24h
what happens if the UT-A2 KO transporter is faulty?
Very mild phenotype only observable on a low protein diet
How important is the UT-B KO transporter?
Increase urine production
Reduced urine concentrating ability
Weight loss
What happens if there is a point mutation in UT-A2?
Reduced BP
What happens if there are function mutations in UT-B?
Reduction in urine concentrating ability
What does the vasa recta do?
Permeable to water and solutes
Water diffuses out of descending limb and solutes diffuse into descending limb, in ascending limb the reverse happens.
Thus oxygen and nutrients are delivered without loss of gradient
What does vasopressin do in kidneys?
Binds to specific receptors V2 on basolateral membrane of principle cells in the collecting ducts causing insertion of aquaporins (AQP2 in luminal membrane) in cell membrane so increase water permability
Where is vasopressin synthesised?
Transcribed and processed in the hypothalamus and packaged into granules.
Where is vasopressin secreted?
Secreted from posterior pituitary (neurohypophysis)
What is vasopressin derived from?
Single transcript that also encodes neurophysin II and copeptin
