The skin is one of several organ systems participating in maintaining a core temperature, meaning the temperature near the center of someone’s body. Temperature sensors in the skin and internal organs monitor core temperature and transmit signals to the control center located in the hypothalamus, a region of the brain. When the core temperature falls below its set point, the hypothalamus: 1. Sends more nerve impulses to blood vessels in the skin that cause the vessels to narrow, which restricts blood flow to the skin, reducing heat loss. 2. Stimulates the skeletal muscles, causing brief bursts of muscular contraction, known as shivering, which generates heat. When the core temperature rises above its set point, the hypothalamus: 1. Sends fewer nerve impulses to blood vessels in the skin, causing them to dilate, which increases blood flow to the skin and promotes heat loss. 2. Activates the sweat glands, and when sweat evaporates off the skin surface it carries a large amount of body heat with it.