7. People produce sweat when they are hot - Edexcel - GCSE Biology - Question 7 - 2020 - Paper 1

Urea is produced in the body primarily through the process of deamination. During this process, excess amino acids are broken down in the liver. This involves removing the amino group from amino acids, which is then converted into ammonia and subsequently into urea, which is less toxic and can be excreted by the kidneys.

The organ that removes most urea from the blood is the kidney.

The hypothalamus controls body temperature.

During hot weather, the body employs several structures in the skin to reduce temperature:

1. Sweat Glands: These glands produce sweat, which is secreted onto the skin's surface. As the sweat evaporates, it cools the skin, helping to lower the body temperature.

2. Hair: The erector muscles associated with hair follicles relax, allowing hairs to lie flat. This reduces insulation and allows for better heat loss from the skin.

3. Capillaries: Capillaries expand (vasodilation) to allow more blood to flow close to the surface of the skin. This increases heat loss through convection and radiation, allowing more heat to escape from the body.

4. Nerve Endings: Nerve endings detect changes in temperature and send signals to the brain. This allows for appropriate responses, such as sweating and increased blood flow to the skin.