Warming

• what is vasoconstriction


  arterioles constrict, arteriovenous shunt vessels dilate

  • little blood flows through capillary networks close to surface of the skin
  • skin looks pale and little radiation occurs
  • warm blood kept well below surface
• sweating


  rate of sweating and production will stop entirely

  • greatly reduces cooling by evaporation of water from skin surface
  • evaporation from lungs still occurs
• hair/feathers

  erector pilli muscles contract, traps an insulating layer of air, so reduces cooling through skin

  • very effective way to reduce heat loss in many animals, with little effect on humans
• shivering


  rapid, involuntary contracting and relaxing of large voluntary muscles in body

  • metabolic heat from exothermic reactions warm up the body, effective method
• anatomical features

  • minimise SA:V ratio
  • thick layer if insulating fat underneath skin
  • hibernation - fat build up, insulated shelter, lower metabolic rate