Controlling body temperature
Body temperature (Supplement)
- The brain detects body temperature and keeps it steady.
- The skin helps, using sweat glands, hair erector muscles, blood vessels and fatty tissue.
Too hot
- sweat glands make sweat; as it evaporates it cools the skin.
- the arterioles widen (vasodilation), so more blood flows to the skin's capillaries and loses heat.
Practice
When you are too hot, the skin loses heat by:
Heat is lost by sweat evaporating and by vasodilation, which brings more blood to the skin surface.
Practice
Vasodilation means the arterioles widen so more blood flows near the skin surface.
Vasodilation widens the skin arterioles, increasing blood flow to the surface so more heat is lost.
Too cold
- you shiver — the muscles make heat.
- the arterioles narrow (vasoconstriction), so less blood reaches the surface, keeping heat in.
- a layer of fatty tissue under the skin gives insulation.
Practice
When you are too cold, the body keeps heat in by:
Shivering generates heat and vasoconstriction reduces blood flow to the surface, keeping heat in.
You've got it
Key idea
- the brain keeps body temperature steady; the skin does the work (Supplement)
- too hot → sweating + vasodilation (more blood to surface)
- too cold → shivering + vasoconstriction (less blood to surface)