1. Definition
   1. maintenance of a constant internal environment
2. 6 Areas to control
   1. body temperature
      1. enzymes
         1. 37C
         2. too high or low not work
         3. death possible
      2. thermoregulator centre
         1. in brain
            1. hypothalamus
         2. personal thermostat
         3. receptors
            1. temperature of blood in brain
         4. skin
            1. impulses about skin temperature
      3. too hot
         1. hairs lie flat
         2. sweat
            1. sweat glands
            2. evaporates
            3. removes heat
         3. blood vessels to skin
            1. dilate
            2. more blood closer to surface
            3. heat transferred from blood to environment
      4. too cold
         1. hairs stand up
            1. trap air
            2. insulating layer
            3. goose bumps
         2. no sweat
         3. blood vessels constrict
            1. close off skin blood supply
            2. frost bite
            3. kills cells
            4. goes black
         4. shiver
            1. muscles contract automatically
            2. respiration
            3. energy
   2. water content
      1. kidneys
   3. ion content
      1. kidneys
   4. blood sugar
      1. see separate topics
   5. waste products
      1. carbon dioxide
         1. respiration
         2. lungs
            1. breath out
      2. urea
         1. excess amino acids
         2. kidneys
3. kidneys
   1. 3 main roles
      1. remove urea from blood
         1. filtered by kidneys
            1. excreted as urine
      2. adjust ions in blood
         1. sodium
            1. taken in by food
            2. absorbed into blood
         2. wrong ion content
            1. water drawn from cells
            2. osmosis
         3. sweat
            1. loss of some ions
            2. salty taste
         4. balance maintained by kidneys
      3. adjust water content of blood
         1. into body
            1. food
            2. drink
         2. lost from body
            1. breathing out
            2. urine
            3. sweat
         3. control
            1. liquds consumed
            2. sweat out
            3. excreted by kidneys
            4. urine
         4. not control
            1. amount breathed out
         5. cold day
            1. no sweat
            2. more urine
            3. pale
            4. dilute
         6. hot day
            1. sweat lot
            2. less urine
            3. dark
            4. concentrated
            5. replace water
            6. food
            7. drink
         7. DIALYSIS MACHINE
            1. same job as kidneys
            2. kidney failure
            3. 3-4 hours / 3 times a week
            4. to big to carry
            5. difficult for people with kidney failure
   2. artery : red
   3. Vein : blue
   4. sphincter muscle below bladder above urethra
4. liver
   1. proteins not stored by body
      1. convert
         1. fats
         2. carbohydrates
         3. waste product
            1. UREA
            2. poisonous
            3. released into blood stream
         4. can be stored by body