The circulatory system helps in thermoregulation by vasoconstriction and vasodilation of blood vessels.

Thermoregulation is the regulation of heat dissipation from the body. When the body is hot sweat is released from the skin, and when cold less sweat is released from the skin, so less heat energy is lost. This is due to the thermoregulation function of the blood vessels.

Vasoconstriction is when the blood vessels of the skin (arterioles) constrict reducing the flow of the blood to the skin, which reduces the amount of heat loss from the blood vessels of the skin. This conserves heat. Vasodilation occurs when the blood vessels of the skin dilate, and the flow of the blood to the surface is increased. An increased flow of blood to the skin increases the amount of heat loss from the blood vessels of the skin to the environment, increasing heat loss. Vasodilation can also occur to increase oxygen delivery.

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Key Points

• Vasoconstriction warms the body by reducing heat loss from the blood vessels of the skin.

• Vasodilation cools the body by increasing heat loss from the blood vessels of the skin.

Key Terms

vaso: related to blood vessels

constrict: become narrow

dilate: become wide