Control of Plasma Osmolarity Flashcards
What is osmolarity?
The concentration of a solution expressed as the total number of solute particles per litre
What detect changes in osmolarity?
Hypothalamic osmoreceptors
Where are osmoreceptors located?
OVLT (organum vasculosum laminae terminalis) in hypothalamus
What two pathways can be triggered by osmoreceptors?
Thirst
ADH
What happens when there is water deprivation?
Increase in plasma osmolarity Stimulation of osmoreceptors Increase ADH secretion - thirst - renal water retention
What happens when there is water intake?
Decrease in plasma osmolarity Osmoreceptor block ADH secretion reduced Increase renal water excretion Diuresis
When is thirst triggered?
When dehydration surpasses the kidney’s ability to cope
Which aquaporins are most sensitive to ADH?
AQP2
What is the counter current mechanism?
Way of generative a vertical concentration gradient in the kidney
How is the concentration of urine determined?
Juxtamedullary nephron - LOH creates vertical osmotic gradient
Vasa recta maintain gradient
CD + ADH
How does the descending limb help create an osmotic gradient?
Highly permeable to water due to AQP1
Impermeable to Na - Na remains in lumen and increases osmolarity
How does the ascending limb help create an osmotic gradient?
Actively transports NaCl out of lumen into interstitium
Impermeable to water
NaCl leaves and water stays - decreases osmolality
How does urea help to create an osmotic gradient?
Urea is reabsorbed from the medullary CD
Moves back into loop of Henle
What maintains the osmotic gradient?
Vasa Recta
How do the vasa recta maintain the gradient?
Flow countercurrently to nephron
