ions

• sodium is taken into the body as food, and then absorbed into the blood.
• if the ion content is wrong, this can upset the balance between ions and water, meaning too much or too little water is drawn into cells by osmosis. having the wrong amount of water can damage cells meaning they don't work as well.
• some ions are lost in sweat. this amount is not regulated so the right balance of ions in the body must be maintained in the kidneys. the right amount of ions are reabsorbed into the blood after filtration and the rest is removed from the body in urine