B3- keeping internal conditions constant

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controlling internal conditions

  • controlling internal conditions is called homeostasis
  • temp, blood glucose, water, ion content must all be controlld
  • waste products needed to be removed are- co2, urea 
  • too mcuh water in cells can cause them to burst and too little the inside can pull away from the membrane

human kidney

  • two kidneys filter the blood
  • urine is produced by;
  • 1. filtering the blood
  • 2. reabsorbing ions and water
  • 3.releasing urea and excess ions and water
  • if glucose is in urine you may have diabetes
  • urine is tempory stored in bladder before removal


  • if a person suffers with kidney failure they use dialysis
  • in a dialysis machine blood flows between partically permeable membranes
  • dialysis process:
  • 1.blood taken from arm
  • 2.thinners prevent clotting
  • 3.dialysis fluid removes urea
  • 4.clean blood flows through bubble trap
  • 5.blood returns to vein
  • in the dialysis fluid there is the same concentration of useful substances as the persons blood substances dont diffuse out
  • urea diffuses out of blood
  • needs to be carried out a regular intervals 

kidney transplant

  • kidneys can be donated or taken from someone who died or was in an accident
  • they must be a good…


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