GCSE Biology (AQA)

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Vasoconstriction & Vasodilation

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Homeostasis and Response The Human Nervous System

Vasoconstriction & Vasodilation

1:51 Control of Body Temperature
Spec 4.5.2.4
Previous Thermoregulatory Centre Next Shivering & Sweating
  • Heat energy is transferred from our bodies to the environment via the skin.
  • Heat loss also occurs through the lungs and excretions.
  • The desirability of heat loss depends on body temperature; it's beneficial when hot and undesirable when cold.
  • Blood vessels near the skin help regulate heat loss.
  • When cold, the body reduces blood flow near the skin, causing vasoconstriction, which reduces heat loss.
  • Vasoconstriction involves the narrowing of blood vessels at the skin's surface, triggered by nerve impulses from the brain.
  • The opposite of vasoconstriction is vasodilation, which occurs when the body is hot.
  • Vasodilation increases blood flow near the skin, making blood vessels more visible and the skin redder or darker, thus increasing heat loss.
  • Vasodilation is the widening of blood vessels at the skin's surface, also controlled by nerve impulses from the brain.

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