The hypothalamus is the part of the brain that is often compared to a thermostat due to the way it regulates a variety of body functions. The hypothalamus is a small but complex structure located at the base of the brain, and it plays a key role in regulating body temperature, hunger and thirst, sleep and wake cycles, and other important functions. Like a thermostat, the hypothalamus is able to sense changes in the body's internal environment and make adjustments to maintain a stable internal balance, or homeostasis.