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Thermoregulation

Animals regulate their body temperature using a process called thermoregulation. Thermoregulation is crucial, as it helps to maintain the body at the optimal temperature for its enzymes.

Some animals live in thermostable environments, such as the open ocean, and have to do very little to maintain their body temperature. Instead, their enzymes are adapted to work at their environmental temperature.

Environments with fluctuating temperatures provide the greatest challenge for thermoregulation.

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Heat transfer

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How is heat gained and lost?

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Ectotherms and endotherms

There are two major strategies for thermoregulation in the animal kingdom: endothermy and ectothermy.

Ectotherms do not exert physiological control over their internal body temperature. They instead rely on external sources of heat to warm their bodies. Despite this, many ectotherms maintain a near-constant body temperature during their hours of activity. Reptiles and amphibians are ectotherms.

Endotherms generate their heat metabolically. Most also maintain a constant internal body temperature, higher than the external environment. Mammals and birds are endotherms.

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Thermoregulation in ectotherms

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Thermoregulation in endotherms

Endotherms generate most of their heat metabolically. As they are warmer than their environment they tend to lose body heat to their surroundings.

Adaptations for heat conservation include:

Insulation – insulating layers of fat, fur or feathers to prevent heat loss.

Metabolism – metabolic rate can be varied to generate more or less heat.

Endotherms also use their skin to vary their rate of heat loss and maintain a constant core body temperature.

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The importance of the skin

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Thermoregulation in humans

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Hyperthermia and hypothermia

Prolonged exposure to high temperatures can lead to hyperthermia. The body’s core temperature rises above 41°C, causing its thermoregulatory mechanisms to break down.

If the body’s core temperature falls below 35°C a person may suffer from hypothermia. Again, the body’s thermoregulatory mechanisms fail and positive feedback occurs, leading to a further decrease in temperature.

When this happens, positive feedback occurs and the person’s body temperature can spiral out of control. A core body temperature of 43°C and higher usually causes death.

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Physiological thermoregulation

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Thermoregulatory control system