Homeostasis is the response to changing conditions that keeps the body in a stable state. Nerves ensure that temperature remains steady whilst hormones keep blood sugar at the correct concentration.
Negative feedback control brings about changes that help return the body to normal conditions. If the body temperature drops, negative feedback control raises the temperature back to normal. If the body temperature rises, negative feedback control lowers the temperature back to normal.
All of the methods to regulate body temperature mentioned so far are involuntary responses - we do not consciously decide to sweat or to shiver. In contrast, humans are also able to make voluntary responses, for example when we decide to take action to help regulate our body temperature.
Examples of voluntary responses when the environment is hot:
Examples of voluntary responses when the enivronment is cold: