Your brain, quietly floating in your skull, appears to be doing nothing, yet it processes billions of bits of information every second about what's going on, in and around you, every moment. It sends out billions of commands: how fast your heart should beat, blood chemistry changes, blood pressure, how to throw a football, bake cookies and what to wear. It's through your brain that you remember millions of memories and express the plethora of feelings, moods, emotions, and inspirations that make you uniquely you.
At the bottom of your skull is a large hole called the "foramen magnum." Your brain extends through this hole as a cable of billions of nerve fibers that become your spinal cord. Spinal cord nerves connect your brain to your heart, lungs, arms and legs. That's how you know that a mosquito is on your ankle.