OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What does vasodilation refer to?

1. Constriction of blood vessels

2. Increase in heart rate

3. Dilation of blood vessels near the skin surface

4. Decrease in sweat production

The correct answer is: Dilation of blood vessels near the skin surface

Vasodilation refers to the process by which blood vessels, particularly those near the surface of the skin, widen or enlarge. This response occurs in various situations, such as when the body needs to release excess heat or increase blood flow to certain areas. During vasodilation, the smooth muscles in the walls of the blood vessels relax, allowing more blood to flow through, which can also enhance the delivery of oxygen and nutrients to tissues. When the skin's blood vessels dilate, more blood reaches the surface, facilitating heat loss through radiation and convection. It's an important mechanism for thermoregulation, helping to maintain the body's core temperature within a narrow range. If the body is too hot, vasodilation helps to cool it down. In contrast, constriction of blood vessels, an increase in heart rate, and a decrease in sweat production do not describe vasodilation but rather other physiological responses that may occur under different conditions, such as when the body needs to conserve heat or redirect blood flow to vital organs during stress or cold situations. These processes serve different functions in the body’s overall homeostasis.