Thermoregulation

• Purpose of Thermoregulation 


  Balance between heat gain and heat loss, resulting in heat balance in an organism
• Thermoregulation

  • critical for survival as most biochemical and physiological processes are temperature sensitive
  • thermoregulatory mechanisms include structural features, behavioural responses and physiological mechanisms to control heat exchange and metabolic activity
  • thermoregulation in animals is the process by which they maintain an internal temperature within a tolerance range - heat for thermoregulation can either come from metabolism or the external environment
• Adaptive Behavioural Responses

  • to reduce heat gain, some animals shelter from high temperatures and reduce their activity, only emerging to feed in the relative cool of dusk and dawn
  • avoiding daytime sun (eg. resting in shade) reduces heat gain via radiation from the sun and via conduction from hot objects (eg. rocks)
• Physiological Adaptations for Hot Environments

  • sweating: sweat glands open to release water and salt onto the skin, which evaporates and cools the skin - the evaporated water carries heat energy away from the body and lowers the internal temperature (evaporative cooling)
  • panting: expels hot air and brings in cooler air, which helps moisture in the mouth to evaporate quickly, reducing body temperature
• Physiological Adaptations for Hot Environments

  • decrease in metabolic rate: used by endotherms to reduce the amount of heat generated within the body
  • pilorelaxation: muscles attached to hair follicles can be relaxed to flatten the hairs and decrease the layer of hair acting as an insulator
• Structural Adaptations for Cold Environments

  • insulation: surface and internal insulation reduces heat flow from the organism to the environment
  • piloerection: raising fur or feathers
  • countercurrent heat exchange: exchange of heat between 2 fluids (blood) flowing in opposite directions
  • SA:V ratio: lower SA:V ratio = less heat loss
• Behavioural Adaptations for Cold Environments

  • huddling: reduces group's overall SA:V ratio
  • basking in sun: gains heat via radiation
  • lying on hot rocks: gains heat via conduction
  • lying flat to increase body SA: maximises heat gain by radiation and conduction
• Physiological Adaptations for Cold Environments

  • vasoconstriction: a mechanism for heating the body and counteracts a decrease in internal body temperature