Thoughout life everyone tells you that brain is essentially a computer but just like computers your brain would create immense amounts of heat by being in use, so if that's the case how does it cool down.
Is like liquid cooling where the blood transfers the heat away? and if so what is the critical temperature when your blood can no longer cool your brain? Also at what temperature are you at risk of brain damage?
Computers rely on cooling mechanisms like heat sinks( an aluminum alloy mounted over the micro integrated chip) and fan. So far none of these mechanisms are utilized by nature, but analogies like cooling mechanisms in elephants which are in turn considered to be a model quite like the fan.
As the largest land animal, elephant's ears have crucial role in regulating homeostasis. When we see an elephant, it always wave its ears in order to reduce the brain temperature. On the other hand humming birds which are very smaller in size reduces its temperature by flowing blood to its wings. Humming birds wings flutter 90 times a second and it allows them to exchange much of its heat to the environment and the cooled blood is driven back to the brain.
The carotid rete or rete mirabile in birds have been developed for heat exchange. In mammals, a pool of the cool venous blood returns from the nose or head skin, exchanges the heat with warm arterial blood of the carotid artery. These arteries are sub divided into hundreds of small arteries forming a net like structure which significantly improve the heat transfer in brain.
Vascular retia mirabilia are also found in the limbs of a range of mammals. These reduce the temperature in the extremities. Some of these probably function to prevent heat loss in cold conditions by reducing the temperature gradient between the limb and the environment. Others reduce the temperature of the testes increasing their productivity. In the neck of the dog, a rete mirabile protects the brain when the body overheats during hunting; the venous blood is cooled down by panting before entering the net.Reference
In Humans,
The net effect of heat production in the brain and brain cooling keeps the brain cooler than the rest of the body and is achieved by surrounding and bathing the brain with venous blood that has been cooled outside the cranial vault, by bone and fat acting as insulation, by the veins of the face and scalp through conduction, convection, sweat and evaporation and by cooled venous blood flowing through the cavernous and suboccipital cavernous sinuses cooling incoming blood in the internal carotid and vertebral arteries before it enters the brain. The combined effect of the brain cooling system keeps the temperature inside the vault and brain about two to three degrees cooler than the rest of the body. The effect is important enough that some physical anthropologists attribute the extra-large size of the human brain more to its exceptional cooling capacity than to the increase in arterial blood flow that comes with upright posture. Anthropologists refer to human encephalization due to enhanced brain cooling capacity as the "radiator theory". Reference
Also yawning and panting are considered to be mechanisms to reduce brain temperature.
