Water Flashcards
how much of water is intra or extra cellular?
intra - two thirds
extra - one third
what is the role of extra cellular fluid?
nourishes and takes away waste products
where is extra cellular fluid found?
in the plasma, between cells in organs and tissues
what ions and cations does intracellular fluid contain?
mainly K+ and Mg2+
what ions and cations does extracellular fluid contain?
mostly Cl-, Na+ and HCO3
how does osmosis work?
osmotic pressure maintains fluid balance
cell membranes are permeable to water due to aquaporins
permeable to K and Na, constant pumping out of Na and recovery of K
if there is lack of water, what happens?
loss of water increases osmotic pressure
cells lose water and start to shrink
hypothalamus activates thirst sensation and pituitary gland release ADH
renal tubes (kidneys) absorb water
excess water makes cells swell and switches off thirst message, stopping ADH release
what is recommended water?
6-8 glasses a day
1.2 litres
how much sodium is needed?
4g/day
how is sodium exchanged?
food (processed food high in sodium)
lost via faeces and sweat
excretion is controlled by glomerular flirtation and tubular reabsorption
what factors are correlated with hypertension?
which factors aren’t?
high salt intake and blood pressure
potassium and calcium and blood pressure
what happens when blood volume decreases?
aldosterone is released
stimulates Na reabsorption and K loss
what effect does sodium depletion have on the body?
blood viscosity increases and oxygen transport is impaired
excess is retained along with water, results in oedema
interferes with normal circulation
how are potassium levels maintained?
kidneys
inflow - natural and processed foods
outflow - faeces and urine
how does potassium have an effect on the body?
ingested K+ stimulates insulin secretion
excretion by the kidneys is increased by K concentration in extracellular fluid
