Thermoregulation

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Links to the current specifications
AQA
3.5.1 Stimuli, both internal and external, are detected and lead
to a response.
3.5.1 Co-ordination may be chemical or electrical in nature.
3.5.4 Homeostasis is the maintenance of a constant internal
environment.
3.5.5 Negative feedback helps maintain an optimal internal
state in the context of a dynamic equilibrium. Positive feedback
also occurs.
Edexcel
Topic 7 – Run for your life:
15. Explain the principle of negative feedback in maintaining
systems within narrow limits.
16. Discuss the concept of homeostasis and its importance in
maintaining the body in a state of dynamic equilibrium during
exercise, including the role of the hypothalamus and mechanisms
of thermoregulation.
OCR
4.1.1 Communication
4.1.3 Hormones
5.4.2 Animal responses
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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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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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