Homeostasis

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Maintaining Homeostasis
THERMOREGULATION
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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 have 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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What’s in skin?
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The importance of the skin
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Responding to change
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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.
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.
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.
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Physiological thermoregulation
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Thermoregulatory control system
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