Homeostasis and Thermoregulation

Biology Unit 5

Homeostasis and Thermoregulation

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Biology Unit 5
Revision Notes
Topic 7: Run for your life
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 the mechanisms of
Homeostasis is the maintenance of a steady internal state in the body, almost regardless of
changes in either external or internal conditions. The most common way our body maintains
homeostasis is by using negative feedback systems.
Homeostasis during exercise
When we exercise our bodies change rapidly and negative feedback systems are essential in
maintaining our internal state of equilibrium.
There are 2 types of receptors that detect temperature change:
Skin receptors ­ detect external temperature
Medulla ­ receptors in the brain that detect the temperature of the blood.
Impulses are sent to the hypothalamus which is the co-ordination centre for thermoregulation in
the brain. We separate this into the "Heat Loss Centre" and the "Heat Gain Centre".
Heat Loss Centre Heat Gain Centre
Stimulates: Stimulates:
Sweat glands to secrete sweat. Arterioles in the skin constrict
Hair erector muscles to contract
Inhibits: Liver to raise metabolic rate
Contraction of arterioles in skin Skeletal Muscles to contract in
(dilates capillaries) shivering
Hair erector muscles (relax ­
hairs lie flat) Inhibits:
Liver (reduces metabolic rate) Sweat glands.
Skeletal muscles (relax ­ stop
Above or below certain temperatures homeostasis fails. Instead, positive feedback may occur
resulting in a high temperature continuing to rise or a low temperature falling still further. This can
result in hyperthermia or hypothermia and may lead to death.
Text Book: p. 154, 162 - 167

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