Watch Human Body: Pushing the Limits Season 1 Episode 4 Online

The driving force behind every one of us is the most powerful organ in the natural world: the human brain. Our central processing unit generates as many electrical impulses in a single day as all the telephones in the world combined. With new state-of-the-art imagery of this complex, mysterious machine, we reveal how our brain accelerates when faced with intense stress or danger, and taps into its deepest layers to unlock prehistoric survival instincts. * NASCAR driver Clint Bowyer tells us about making split-second decisions in the heat and stress of a 400-lap race. * Desperate firefighters, trapped by the intense heat of a forest fire, find out how the brain can take charge without waiting for conscious control. * A lone explorer, piloting a balloon over the Arctic, pushes himself to the limits of sleep deprivation. It nearly costs him his life. Plus, learn about the extraordinary ways our brains can re-tune our system when starvation threatens, and how sleep and dreams can unleash unseen powers in our mind.