Sodium and Water Balance COPY Flashcards
what hormone controls water balance and where is it secreted from?
ADH (aka vasopressin)
secreted from posterior pituitary
what does ADH do?
makes you pee less by causing water to be reabsorbed from the renal tubules
increased ADH = small volume of concentrated urine
decreased ADH = large volume of dilute urine
what injury can cause a decrease in ADH secretion?
transection of pituitary stalk in head injury
diabetes insipidus
how is urine concentration measured?
urine osmolality
high osmolality = concentrated urine
low osmolality = dilute urine
…
sodium and (potassium?) pumped out of the loop of henle?
what controls sodium balance?
steroids
- aldosterone (mainly)
- other steroids (e.g cortisol)
what do steroids do to control sodium balance?
mineralocorticoid activity
- refers to Na+ reabsorption in renal tubules in exchange for K+/H+
too much mineralocorticoid activity = sodium gain
too little = sodium loss
how do you calculate sodium concentration?
mmol Na+ / 1 L water
how do intra and extracellular fluid differ/
intra = contains more fluid intra = lower Na+ concentration
can water move between all body compartments?
yes
means that if you lose water you loose it from everywhere
can sodium move between all body compartment?
no
confined to the extracellular fluid
- Na+/K+ pump in plasma membrane keeps sodium in ECF
- if sodium is lost its only lost from ECF
how does water balance relate to sodium balance?
water follows solute (sodium is the most abundant solute so water basically follows sodium)
so if you loose or gain sodium, you loose or gain water with it
what are the two possible causes for reduced concentration of sodium?
loss of sodium from the ECF (dangerous) fluid retention (too much water dilutes sodium)
what can cause increase in sodium concentration?
loss of water
increase in ECF sodium
why is loss of sodium from ECF dangerous?
little fluid in ECF anyway
if sodium lost then water will follow causing reduction in fluid volume
will have severe symptoms