There are two thermoregulatory centres in the hypothalamus: the heat loss centre and the heat gain centre.The heat loss centre is activated when the temperature of blood flowing through the hypothalamus increases. Impulses are sent to the skin and muscles through the autonomic nervous system.When the temperature of blood flowing through the hypothalamus decreases it activates the heat gain centre in the hypothalamus which sends impulses through the autonomic nervous system to effectors in the skin and muscles to raise the core body temperature.