What happens to blood vessels when temperature is high?

When the temperature is high, blood vessels dilate. This process, known as vasodilation, occurs as the body seeks to regulate its temperature and dissipate heat. The widening of blood vessels allows for increased blood flow to the surface of the skin, facilitating heat loss through radiation and conduction. This physiological response helps to cool the body down and maintain a stable internal temperature.

In the context of high temperatures, other methods of thermoregulation, such as perspiration, also contribute to cooling the body, but the dilation of blood vessels is a key mechanism that enhances blood circulation and promotes heat transfer from the body's core to the environment.