BRAINCAKEKeeping Warm
When core temperature falls below the norm, the hypothalamus triggers responses that reduce heat loss and increase heat production.
Reducing heat loss
• Vasoconstriction. Arterioles supplying the skin constrict, so less blood flows near the surface and less heat is lost by radiation (see the vasoconstriction lesson).
• Hairs raised. The hair erector muscles contract and pull the hairs upright. A thicker layer of still air is trapped next to the skin. Air is a poor conductor of heat, so this insulates the body. In humans, who have little body hair, this only produces goose bumps.
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Key terms in this lesson
- vasoconstriction
- Narrowing of a blood vessel, which decreases blood flow through it.
- brown fat
- A tissue found especially in newborns and hibernators that releases energy directly as heat instead of making ATP.
More in Homeostasis
- Ectotherms
- Thermoregulation in Endotherms
- The Skin
- Keeping Cool
- Control of Core Body Temperature
- Vasodilation
- Vasoconstriction
- Adaptations for Cold Environments
All 41 lessons in Homeostasis · All Edexcel A-level Biology topics