maintaining water balance

• osmoregulation

  the control of water + mineral salts within the body
• levels are maintained to prevent cells from bursting/shrivelling
• if concentration inside the cell is at equilibrium to the outside the water + salts move in and out of the cell at an equal rate
• hypotonic

  when concentration of salts inside the cell becomes higher than the concentration outside, the solution outside is more dilute; water moves into the cell by osmosis causing the cell to swell and it can burst
• hypertonic

  when the concentration of salts inside the cell becomes lower than the concentration outside the cell, the solution outside is more concentrated; water moves out of the cell by osmosis causing it to shrivel
• water is lost from the body through the lungs when exhaling and the skin by sweating
• mineral ions and urea are dissolved in sweat
• excess water, ions+urea are removed from the body in the urine via kidneys