Thermoregulation

Thermoregulation

1. Poikilotherm

   • temperature same as environment
   • ectotherm
   • invertebrates, fish, amphibia, reptiles

2. Homeotherm

   • endotherm
   • maintain body temperature regardless of environment
   • requires high metabolic rate
   • mammals, birds

3. Heat production

   • increased metabolism
   • muscle contraction
     • shivering
     • exercise
   • non-shivering thermogenesis

4. Heat loss

   • non-evaporative heat transfer to environment
     • convection
     • conduction
     • radiation
   • evaporative heat loss
     • from body surface and respiratory system

5. Factors affecting heat exchange

   • physical
     • weather, size/shape, insulation, colour, peripheral blood flow
   • behavioural
     • too hot
       • avoid sun
         • seek shade, burrow
       • increase evaporative heat loss
         • wallow, spray, lick fur
       • increase non-evaporative heat loss
         • postural changes - spread out to increase surface area
     • too cold
       • reduce sensible heat loss
       • shelter
       • huddle
       • freeze
         • avoids water penetration 

6. Piloerection

   • cold
     • maximum boundary layer
     • increased insulation
   • hot
     • reduced boundary layer
     • decreased insulation
   • controlled by sympathetic innervation

7. Sweat glands

   • evaporative heat loss
   • secretion controlled by sympathetic innervation
   • contents
     • water, urea, lactic acid, sodium, potassium, sometimes protein herbivores preferentially lose potassium so conserves water loss

8. HYPOTHERMIA

   • heat loss exceeds capacity for heat production
   • temperature drops
     • reduced CO and BP, decreased oxygen consumption, increased blood viscosity, reduced mental abilities, lose consciousness 

9. HYPERTHERMIA

   • heat production exceeds ability to lose heat
   • excess water and salt loss

Images and files in the map