PADI Divemaster Certification Practice Exam

How does the body promote cooling in response to heat?

1. Skin cells contract

2. Capillaries dilate for heat transfer

3. Blood vessels narrow

4. Muscle activity increases

The correct answer is: Capillaries dilate for heat transfer

The body promotes cooling in response to heat primarily through the process of capillary dilation, which enhances heat transfer. When the body temperature rises, the blood vessels, particularly the capillaries near the surface of the skin, expand or dilate. This dilation increases blood flow to the surface of the skin, allowing more heat to be released into the environment. The increased blood flow helps to dissipate excess body heat, facilitating a cooling effect. In contrast, skin cells contracting or blood vessels narrowing would actually reduce blood flow to the surface, making it more difficult for the body to lose heat. Similarly, an increase in muscle activity generates additional body heat, potentially exacerbating the issue rather than promoting cooling. Thus, capillary dilation is the most effective mechanism for promoting cooling as it directly aids in the loss of heat from the body to the surrounding environment.