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what is osmoregulation?
process of maintaining water and salt concentrations across membranes within body
example of homeostasis
why is maintaining water levels important?
prevent harmful changes occurring to cells of the body as a result of osmosis
too much water in the blood - causes cell swelling as water moves into them, can lead to cell lysis (bursting)
too little water in the blood - cells lose water by osmosis, dehydrating effect, possible cell death
what are the two sources of water in the body
product of aerobic respiration
diet
how is water lost from the body?
via the lungs during exhalation
sweating
urine
can water loss controlled?
water lost through lungs/skin cannot be controlled
volume of water lost in urine can be controlled by the kidney
is water reabsorption negative or positive feedback?
negative feedback
when feedback causes corrective measures to be turned ‘off’ so system returns to normal level
how is water reabsorpiton controlled?
by ADH
where is ADH released?
pituitary gland
how much ADH is released?
depends on how much water the kidneys need to reabsorb
what does ADH affect?
permeability of the tubules (collecting duct) to water
if water content of blood is too high…
less ADH released
less water reabsorbed in collectign ducts
kidneys produce large volume of dilute urine
if water content of blood is too low…
pituitary gland releases more ADH
more water reabsorbed
kidneys produce small volume of concentrated urine
Note 
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