 Temperature regulation. Have you ever wondered why you sweat when you get too hot from running or shiver on a cold winter's day? Well in this video we are going to explain why your body behaves like this. Humans are endotherms. This means we are warm-blooded. We keep our body operating at 37 degrees Celsius regardless of the external conditions. However this is a real challenge as our environment changes all the time depending on the weather, our clothes, if we are inside by the fire or outside having a snowball fight. So how does this work? Well it's quite similar to the heating system in a house. In a house is a thermostat that measures the temperature. If the house gets cold the thermostat will tell the radiators to turn on and heat it up. If it's too hot they will be told to switch off. Simple. Your body works in just the same way. Here in your brain is a special area called the hypothalamus. It measures the temperature of the blood flowing through it and also collects information from temperature sensors around the body. It then decides if the temperature is too hot or too cold and will try and bring it back to 37 degrees Celsius. If you are too hot the hypothalamus can then send signals out to the body via the nervous system that can cause various effects. It can send a signal to your skin and cause sweat glands to secrete the sweat onto the surface of the skin. The sweat itself is not cold but it works because it takes the heat away from your body in order to evaporate it. Another way of losing heat is vasodilation. Look how these blood vessels nearest the surface of the skin open wide and allow blood to flow through them. The heat is radiated from the blood into the air and the blood cools down. If you get too cold you can do the opposite with these blood vessels and close them off keeping the blood away from the surface of the skin. This is called vasoconstriction. You can also start to shiver. This is when your muscles contract in order to make heat. Another effect you may have noticed when you are cold are goose pimples. If you look more closely at goose pimples what you realize is that each of the little bumps has a hair sticking out of it. These hairs are stood up on end to trap a layer of air around the skin. Air is a fantastic insulator of heat and this will keep you nice and cozy. Did you know that when you pluck a goose it leaves these little bumps and that is where the term comes from. All these effects are examples of negative feedback that help with homeostasis. For more information on these processes watch the video What is homeostasis?