Homeostasis: control in the body

Homeostasis: control in the body

1. WATER LEVEL

   • method
     • in
       • food and drinks
     • out
       • breathing
       • urine and faeces
       • sweat
   • Kidneys regulate water content of the body
     • ADH
       • blood too concentrated, releases ADH
       • kidneys release less water, stays in blood
     • remove excess fluid
       • send to bladder
         • stored then eliminated as urine
   • when hot or exercisng we lose water through sweat
     • we then produce less urine, although it is more concentrated

2. blood glucose level

   • provides energy supply
   • pancreas
     • detects high levels (after a meal)
       • releases insulin
         • stored as glycogen by muscles
     • detects low levels (exercise)
       • releases glucagon
         • converts glycogen back to glucose
   • Diabetics often either don't produce insulin or cant detect it

3. TEMPERATURE

   • methods
     • sweating
       • too cold: no sweating
       • too hot: sweating increases, evaporation cools skin
     • hairs
       • too cold: hairs stand up to trap a layer of air
       • too hot: hairs lie flat
     • shivering
       • too hot: muscle activity reduces
       • too cold: contractions generate heat
     • blood flow to skin
       • too hot: blood vessels dilate , so more blood to skin(vasodilation)
       • too cold: blood vessels constrict, reducing blood flow(vasoconstriction)

4. IONS + SALTS

   • lost through
     • skin as sweat
     • kidneys as urine
   • includes
     • sodium
     • chloride