Suppose you have dropped your pencil on the floor and want to pick it up. This is a very easy thing to do, with hardly any thought or difficulty. Yet this simple action causes you to use dozens of your voluntary muscles.
First, you have to locate the pencil. This requires you to move your eyes, and also to turn your head, until the pencil comes into view. Then you must bend down to reach the pencil, grasp it, and then straighten up again. Not only do dozens of voluntary muscles bring about your motions, but they must do so in just the right order. It would be futile to attempt to grasp the pencil before you bend down to bring your hand within reach. Clearly something is controlling the motions of your muscles. What is it?
It is the brain, the computer you carry about all your life. It looks a little like a gray, pulpy cauliflower, well-protected within a bony skull. It is made up of millions of cells. Nerves from all over the bpdy connect with the brain through the spinal cord and the neck.
Through this vast network of nerves, a huge amount of information reaches the brain from the various parts of the body. Different parts of the brain receive, sort out, store and respond to different parts of the body, particularly to the sense organs; the eyes, the nose, the tongue, the ears and the skin.
It is the brain that sends messages to all your organs, so that automatically the heart beats, the lungs breathe, the digestive system digests.
The body can get along with only one kidney and with an artificial heart and limbs, but without the brain no other part of the body could function. Therefore it can very well be said to be the your most important organ.
The movements of your muscles are controlled by your brain which works through a system of nerves distributed throughout your body. The brain and the nerves, together, make up the body’s nervous system.
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