Thermoregulation in endotherms

• Endotherms = rely on their metabolic processes to warm up and they usually maintain a very stable core body temperature regardless of the temperature of the environment.
• The peripheral temperature receptors are in the skin and detect changes in the surface temperature.
• Temperature receptors in the hypothalamus detect the temperature of the blood in the body.
• The temperature of the skin is much more likely to be affected by external conditions than the temperature of the hypothalamus. The combination of the two gives the body great sensitivity and allows it to respond not only to actual changes in the temperature of the blood but to pre-empt possible problems that might result from changes in the external environment.
• Endotherms use their internal exothermic metabolic activities to keep them warm, and energy-requiring physiological responses to help cool them down.
• Endotherms also use some behavioural responses to control their body temperature (e.g. wallowing in water, digging burrows, hibernation).
• Vasodilation = when our body temperature is too high, arterioles near the surface of the skin dilate. The arteriovenous shunt vessel constricts. This increases the flow of blood to our skin, which increases the transfer of energy from our skin to the environment via radiation.
• Vasoconstriction = when our body temperature is too low, arterioles near the surface of the skin constrict. The arteriovenous shunt vessel dilates. This reduces the flow of blood to our skin, which decreases the transfer of energy from our skin to the environment via radiation.
• The heat loss centre = this is activated when the temperature of the blood flowing through the hypothalamus increases. It sends impulses through autonomic motor neurones to effectors in the skin and muscles, triggering responses that act to lower the core temperature.
• The heat gain centre = This is activated when the temperature the blood flowing through the hypothalamus decreases. It sends impulses through the autonomic nervous system to effectors in the skin and muscles, triggering responses that act to raise the core temperature.