responding to osmotic challenges

• how much water should you consume per day?

  2 litres
• when do you need to take in more water?

  Strenuous exercise, or exposed to high temperatures
• why do you often need to take in more water?

  High temperature increases rate of water loss through sweating and sweat contains water and salts which are then lost from the body
• what triggers the thirst response?

  a reduction in the water potential of your blood plasma or an increase in salt concentration
• what happens after the thirst response?

  an impulse is sent to your brain which informs you to take on more fluids, the kidneys respond by producing less urine
• what is dehydration?


  The condition where you have not taken on enough water into your body
• what are symptoms of dehydration?


  Dark and concentrated urine, headaches/dizziness, and a lack of energy
• what happens if you remain dehydrated?

  The kidneys and liver may suffer permanent damage and can cause death
• what happens to the body when you take in too much water?

  It causes the water potential of your blood plasma to rise above the water potential of your cells and the kidneys respond by increasing the volume of urine produced
• what happens when a large volume of water is consumed rapidly?

  Water will move by osmosis into your cells which may cause cells to burst. the concentration of sodium in the blood plasma also drops
• what happens when concentration of sodium in blood drops?

  Muscle cramping, confusion and seizures
• what happens if water moves into brain cells by osmosis?

  In extreme cases, death
• what are the 3 groups of sports drink?

  hypertonic, hypotonic and isotonic
• what do hypertonic sports drinks contain?

  High levels of glucose and salts
• what do hypotonic sports drinks contain?

  Low levels of glucose and salts
• what do isotonic sports drinks contain?

  Ion concentrations equal to those in the blood plasma
• what sports drinks allow you to rehydrate rapidly?

  Isotonic sports drinks, they have the same concentration as your body fluids and can be absorbed even faster than water
• what are hypotonic sports drinks designed for?

  Replacing fluids quickly that are lost during exercise
• what is the scientific evidence surrounding sports drinks?

  The evidence for the claim that they allow you to improve your performance as an athlete is limited and not all scientists believe it
• what is a dependent variable?


  The variable that is being measured or observed in an experiment.
• what is an independent variable?


  The variable that is changed by the researcher in an experiment.
• what is the control variable?

  The control variable is the variable that is kept constant or unchanged