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

What happens when the body temperature decreases?

1. Erector muscles contract, hairs stand on end

2. Sweating increases

3. Blood vessels dilate

4. Respiration halts

The correct answer is: Erector muscles contract, hairs stand on end

When the body temperature decreases, the correct physiological response involves the contraction of erector muscles, which causes hairs to stand on end. This process is part of the body's mechanism to conserve heat. When the erector muscles contract, they pull the hair follicles upright, creating an insulating layer of air close to the skin. This action helps to reduce heat loss from the surface of the skin, which is particularly important during cold conditions. In contrast, sweating increases with rising temperatures as a cooling mechanism, blood vessels dilate to release heat in a process known as vasodilation, and respiration does not halt due to temperature changes unless there are severe medical conditions present. Each of these responses serves a distinct function that is not activated when body temperature decreases, highlighting the significance of the hair standing on end as a means of thermoregulation.