Human: The World Within

An introduction to the amazing functions of the human body's nervous system. This extremely advanced part of our biology is always at work interpreting the world we encounter and helping us decide what to do, and how to react. The secrets of our thoughts and decisions are locked into this astonishing network of cells, nerves, and fibers.

Pain is a phenomenon that is deeply intertwined with the brain and nervous system. When something is wrong with the body, signals travel to our brain as neural impulses. These impulses are then interpreted by the brain as pain, which is basically the body's signal to us that we need to fix something.

The brain is mission control of the human body and the nervous system. Its 100 billion cells are processing data an incredible speeds. The brain coordinates not only the major functions of the body, but it also is the hub where information is interpreted and stored, and then turned into action. We have the brain to thank for the unique abilities of our species.

Jason Little lost his hand in a car accident, which he thought meant the end of being able to sense touch in that part of his body forever. Years later, he's now the first user of a new wireless interface that connects to his prosthetic arm and allows him to actually feel things in his phantom limb. His brain is able to interpret new signals in a way they once did.

All sight is translated into electrical impulses via the retina to the brain. The eye picks up information in the form of light. This light is instantaneously transformed into electricity, which shoots up to the brain. Once there, the electricity is decoded and formed into a picture. The information is traveling at speeds nearing 300mph, and the stream of data never stops.

Through the lens of a boxer, a first responder, a cell tower climber and a man with a bionic limb, go deep into the universe of the most powerful machine on earth: the human brain and the vast nervous system it controls.

The experience of smell starts when air molecules meet tiny little hairs in our nasal cavity. These hairs are called cilia, and they trap the incoming fumes so they can be processed.

An introduction into the amazing functions of the human body's five senses. Our bodies are constantly absorbing different kinds of information from the outside world. Sights, sounds, smells, tastes, feelings. Inside the body all of these things are pieced together to create our individual reality.

When we lose one of our senses, the loss isn't something the body can't handle. It just means that the brain has to figure out a new way of filling the void left by the information that's no longer there. Our bodies are actually incredibly adaptable when it comes to compensating for missing sensation.

It doesn't usually make the list of the five most important human senses, but proprioception is fundamental. It's our sense of where our bodies exist in space. We can feel where our hand is or where our feet are without looking at them. And we can move them accordingly because of that innate sense.

Dive into the stories of a pairs figure skating team, a perfumer, a cave explorer and a musician to decipher how different ways of sensing the world all create their own vivid and unique picture.

Look at a nature survivalist, rancher twins, a doctor who survived Ebola and the recipient of a cutting-edge cancer therapy to uncover the wildly advanced biology that keeps us alive against all odds.