Emergency Medical Technician (EMT) Intermediate Practice Exam

How do the blood vessels of the skin respond to cold temperatures?

1. Dilation, allowing more blood to the skin

2. Constriction, which diverts blood away from the skin

3. No change in blood vessel size

4. Control by the nervous system

The correct answer is: Constriction, which diverts blood away from the skin

When exposed to cold temperatures, the blood vessels of the skin primarily respond by constricting. This constriction is a physiological mechanism that helps to reduce blood flow to the skin's surface, thereby conserving body heat and maintaining core body temperature. By diverting blood away from the skin, the body minimizes heat loss through the surface of the skin, as less warm blood is brought to the periphery where it could be cooled by the external environment. While the nervous system does play a vital role in regulating this response, the primary action in cold exposure is the constriction of blood vessels. Other options, such as dilation, would counteract the body's need to preserve heat, while a lack of change would not address the necessity of thermoregulation in cold conditions. Therefore, understanding the body's response to varying temperatures helps in comprehending the mechanisms behind thermoregulation and how the body maintains homeostasis.