Homeothermy and temperature regulation

  1. Definitions

    1. Ectothermy
    2. Endothermy
    3. Homeothermy

  1. Costs and benefits of homeothermy

    1. Costs

      1. Increased energy requirements
      2. Increased susceptibility to thermal stress

    1. Benefits

      1. Ability to be active in otherwise inhospitable environments
      2. Freedom from dependence on sunlight to regulate body T
      3. Increased ability to sustain a high level of activity

  1. How is body temperature maintained ( thermoregulation )?

    1. Environmental heat loss/gain
    2. Thermal inertia
    3. High resting metabolic rates
    4. Tactics to balance internal heat production with environmental heat gain/loss

Tactics used to retain heat
  1. Hair
  2. Blubber
  3. Shivering
  4. Blood vessel specializations ( regional heterothermy)

    1. counter-current heat exchange
    2. vasoconstriction

  5. Big body size
  6. Huddling (if with others) or curling up (if alone)
    alternate image of curling up
Tactics used to dissipate heat
  1. Evaporation
    1. Sweating
    2. Panting (respiratory vapor)
  1. Behavioral thermoregulation
  2. Nocturnal activity
  3. Hair
  4. Heat loading

  1. Characteristics of endothermy

    1. Thermoneutral zone: The range of temperatures at which no extra energy is required to maintain homeothermy.

    1. Lower critical temperature: The lower temperature threshhold at which the animal has to increase its metabolism to maintain body temperature.

    1. Upper critical temperature: The upper temperature threshhold at which the animal has to increase its metabolism to cool the body.

    1. Scaling of metabolic rate to body size in endotherms

  1. Special temperature regulation strategies

    1. Hypothermia

      1. Benefits
      2. Can be daily, seasonal
      3. Examples: Insectivores, Microchiroptera, some primates, carnivores, rodents
      4. Characteristics of the hypothermic state

        1. Decreased heart rate
        2. Shivering is suppressed
        3. Respiration rate is reduced
        4. Oxygen consumption is reduced
        5. Vasoconstriction of periphery

      1. Warming back up

        1. Metabolism of brown fat
        2. Shivering