Sodium and Water Balance Flashcards
What is the key hormone that controls water balance?
ADH
What is the key hormone that controls sodium balance?
Steroid hormones from the adrenals
Where is ADH released from?
Posterior pituitary
What is another name for ADH?
Arginine Vasopressin
What does an increase in ADH secretion cause in the urine?
Small volume of concentrated urine
What does a decrease in ADH cause?
Large volume of dilute urine
What is the meaning of urine osmolality?
A measure of urine concentration, in which large values indicate concentrated urine and small values indicate diluted urine
What does ADH cause in the kidney?
Causes the kidneys to reabsorb water
How does ADH cause water resorption?
Countercurrent multiplication
What is mineralocorticoid activity?
Na+ reabsorption in renal tubules in exchange for K+/H+
What is the steroid with the main mineralocorticoid activity?
Aldosterone
What does an increase in mineralocorticoid activity cause?
Sodium gain
What dies a decrease in mineralocorticoid activity mean?
Sodium loss
What scenarios would result in hyponatraemia?
Decreased sodium
Water retention
What scenarios would result in hypernatraemia?
Increased sodium
Water excretion
In which fluid compartment is most of the water in the body stored?
Intracellular fluid compartment
In which fluid compartment is there a higher concentration of sodium?
Extracellular fluid compartment
What factors are present to keep intracellular Na+ levels relatively constant?
Na+/K+ ATPase
If sodium is lost from the body, which compartment is it lost from?
ECF since this is where sodium concentration is confined
What is the significance of losing Na+ from the ECF?
Water follows Na+ by osmosis therefore if you lose Na+ from the ECF, water will follow it resulting in a loss of water from the DECF alone and not from the ICF
What is the most common type of sodium-water imbalance?
Decreased water excretion from SIADH leading to Hyponatraemia
