Temperature control

Biology · Coordination and control. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.

Test this topic free All Biology topics

The idea

Mammals keep their internal body temperature constant. The hypothalamus in the brain detects the temperature of the blood and coordinates the responses. Temperature receptors in the skin detect changes outside and send impulses along sensory neurones to the brain.

When the body is too hot, sweat glands release sweat, and arterioles supplying the skin capillaries widen (vasodilation). More heat is lost from the skin.

When the body is too cold, the arterioles narrow (vasoconstriction), muscles shiver, and hair erector muscles contract so the hairs stand up. Fatty tissue under the skin is an insulator, so it slows heat loss all the time.

Rules to remember

Sweating: water in sweat evaporates, taking heat energy from the skin.
Vasodilation: arterioles widen, more blood flows through skin surface capillaries, more heat is lost.
Vasoconstriction: arterioles narrow, less blood flows through skin surface capillaries, less heat is lost.
Shivering: muscles contract rapidly, respiration in them increases and releases heat.
Hair erector muscles contract: hairs stand up and trap a layer of air, which insulates.
Fatty tissue under the skin insulates and reduces heat loss.
Hypothalamus: detects blood temperature and coordinates the responses.

Common mistake

Blood vessels do not move up or down in the skin, and capillaries do not change width. It is the arterioles that widen or narrow, which changes how much blood flows near the surface.

Worked example

A person walks out of a warm house into freezing air and the skin of the face soon looks pale. Explain why.

Temperature receptors in the skin detect the cold and send impulses to the brain.
The arterioles supplying the skin surface capillaries narrow (vasoconstriction).
Less blood flows through the capillaries near the surface, so the skin looks paler.
With less warm blood near the surface, less heat is lost to the air.

Answer: Vasoconstriction reduces blood flow near the skin surface. This makes the skin pale and reduces heat loss.

Ask about this

Type what you are stuck on. The helper finds the explanation, worked examples and the notes to read, free and instant.

Read the full notes

Homeostasis

Keep going

← Homeostasis Blood glucose control →Take a Biology test