Maintaining stable body conditions

Homeostasis is the response to changing conditions that keeps the body in a stable state. Nerves ensure that temperature remains steady whilst hormones keep blood sugar at the correct concentration.

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What does the body do when it is too hot?

Increased rate of sweating

The hypothalamus sends messages to the sweat glands resulting in increased sweat production.
Heat energy from the body will convert the water in sweat to water vapour.
This lowers the body temperature.

Vasodilation

Blood vessels called arterioles near the surface of the skin dilate (get wider) allowing more blood to the skin surface where more heat can be lost by radiation.

Vasodilation occurring within the skin. Nerve impulses are received from the hypothalamus, the arteriole becomes dilated and as it passes under the surface of the skin heat is lost through radiation.

Relaxation of hair erector muscles

This prevents heat being trapped in a layer of air next to the skin.

2 images of hair erector muscles. In the first the hairs are relaxed, in the second they are upright.