Thermoregulation

Poikilotherm
1. temperature same as environment
2. ectotherm
3. invertebrates, fish, amphibia, reptiles
Homeotherm
1. endotherm
2. maintain body temperature regardless of environment
3. requires high metabolic rate
4. mammals, birds
Heat production
1. increased metabolism
2. muscle contraction
  1. shivering
  2. exercise
3. non-shivering thermogenesis
Heat loss
1. non-evaporative heat transfer to environment
  1. convection
  2. conduction
  3. radiation
2. evaporative heat loss
  1. from body surface and respiratory system
Factors affecting heat exchange
1. physical
  1. weather, size/shape, insulation, colour, peripheral blood flow
2. behavioural
  1. too hot
    1. avoid sun
      Annotations:
      - seek shade, burrow
    2. increase evaporative heat loss
      Annotations:
      - wallow, spray, lick fur
    3. increase non-evaporative heat loss
      Annotations:
      - postural changes - spread out to increase surface area
  2. too cold
    1. reduce sensible heat loss
    2. shelter
    3. huddle
    4. freeze
      Annotations:
      - avoids water penetration
Piloerection
1. cold
  1. maximum boundary layer
  2. increased insulation
2. hot
  1. reduced boundary layer
  2. decreased insulation
3. controlled by sympathetic innervation
Sweat glands
1. evaporative heat loss
2. secretion controlled by sympathetic innervation
3. contents
  Annotations:
  - water, urea, lactic acid, sodium, potassium, sometimes protein herbivores preferentially lose potassium so conserves water loss
HYPOTHERMIA
1. heat loss exceeds capacity for heat production
2. temperature drops
  Annotations:
  - reduced CO and BP, decreased oxygen consumption, increased blood viscosity, reduced mental abilities, lose consciousness
HYPERTHERMIA
1. heat production exceeds ability to lose heat
2. excess water and salt loss

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Thermoregulation

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	Created by Joanne Wills about 8 years ago