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Brain

 

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Overview
Imagine what your own brain looks like inside your head. It is pinkish gray on the outside, yellowish white on the inside, and covered with ripples or convolutions. The brain has a delicate consistency, like soft ice cream, and requires the shell-like skull to protect it from injury. Although it may not seem like it, you have just performed an amazing feat. You have used your brain to think about itself. As far as we know, human beings are the only animals on Earth who can contemplate their own brains. If you take a close look at a human brain, you'll find it has three main parts. By far, the largest is the cerebrum on top. The intricate surface of the cerebrum is called the cerebral cortex. Although only 0.3 centimeters (1/8") thick, the cerebral cortex is critical to your ability to move as you please, to understand what you see and hear, and to do the complex process called thinking--making decisions, learning, analyzing, remembering, planning, and contemplating. Your cerebrum is divided into two halves. Each has specialized functions. An "electric highway" of nerve fibers, the corpus callosum, connects the two, allowing information to pass between. At the back of your brain and beneath the cerebral cortex is the cerebellum. It coordinates skilled movement, giving you the ability to juggle, dance, type, walk without stumbling, and drink without slobbering. Located at the base of the brain is the brain stem, a stalklike structure that connects it to the spinal cord. The brain stem takes care of basic, involuntary functions, such as breathing, blinking, and keeping your intestines churning. Every part of the human brain is made of billions of nerve cells called neurons. Each neuron has connections to thousands of other neurons. For you to read this (or even to daydream), millions of your neurons must communicate with one another. A neuron accepts signals from other neurons through branchlike structures called dendrites. Whenever enough messages arrive from neighboring neurons to excite it, a neuron sends an electrical impulse down its trunklike axon. When the impulse arrives at the end of the axon, it causes little sacs to release chemical messengers. These chemicals, called neurotransmitters, then travel across tiny gaps called synapses to arrive at and excite other neurons. When you learn something new, your neurons actually grow more dendrites to reach other neurons. The more you practice, the stronger these connections become. With 100 trillion possible connections, your brain is one of the most complex regions in the universe. When are you most aware of your brain in action? Which parts of your brain do you think are active when you sleep? What does information overload feel like? When, if ever, has it happened to you? Do you think your brain is similar to a computer? Why do some researchers compare a single neuron in the brain to a computer?

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