”I am Your Body”

BRAIN

    
COMPARED TO ME, other wonders of the universe pale into insignificance. I am a three-pound mushroom of gray and white tissue of gelatinous' consistency. No computer exists that can duplicate all my myriad functions. My component parts are staggering in number: some 30 billion neurons and five to ten times that number of glial cells. And all this fitted into the crown of a size 7 hat! I am your brain.
But I'm not just part of you, I am you-your personality, your reactions, your mental capacity. You think that he hear with your ears, taste with your tongue, feel with your fingers. All these things happen inside, of me-ears, tongue and fingers merely gather information. I tell you when you are sick, when your hungry; I govern your sex urge, your moods, everything.

Even when you're asleep I continue to handle traffic that would swamp all the world's telephone exchanges. The amount of information flooding in on you from the outside is staggering. How can I cope with it all? I simply select what is important, and you ignore the rest. If you put a phonograph record on and attempts to read at the same time, you will concentrate on the record or the book, but not both. If you become involved in a particularly good novel, you shouldn't be surprised if you don't remember hearing your favorite musical passage.

Of course, if something potentially dangerous happens, I instantly shift gears. You slip on the ice and I immediately direct you to regain your balance, and then signal your arms to break the fall. Finally, if you hit the ground, I let you know if you're hurt. And the event is stored in my memory to warn you to walk carefully on ice in the future.

In addition to taking care of such emergencies, I have thousands of housekeeping 'chores' to perform. Overseeing breathing, for example. Sensors inform me that carbon dioxide is rising in your blood and that you need more oxygen. I step up the breathing rate-timing the contraction, and relaxation of chest muscles.

In thousands of such ways I baby you. In return, I am piggishly demanding. Although I represent only two percent of your body weight, I require 20 percent of the oxygen you inhale and a fifth of the blood your heart pumps. I am utterly dependent on a constant supply. Let there be a temporary shortage and you faint. Let the supply be cut off for a few minutes and I suffer grave damage-paralysis or death may result. I also demand a steady, supply of nourishment-glucose. Even in situations of acute starvation, I get first call on any available, for without me you would die.

In many respects, I am like a vast, unexplored continent, with little more known than the rough outlines of the shore. But the researchers who are attempting to map me have come up with some fascinating information. For example, although all pain is felt in me, I myself have no pain sensation even when I'm cut. Thus, brain surgery is performed with the patient wide-awake, allowing the brain explorers to stimulate specific areas of me electrically and observe the response. If you ever undergo such surgery, you will be amazed at what can happen. A tickle of electricity in one place and you might "see" a, long-forgotten third-grade teacher. Stimulated in other places, you might "hear" a train whistle or a recitation of a nursery rhyme you couldn't have recalled a few hours earlier. I'm like an old attic containing mementos of a lifetime. You might not be aware of what it is in the attic, but it's there.

The brain mappers have at least a rough 'outline' of my primary functioning areas: vision in the rear, hearing on the sides. Perhaps the most interesting discovery is the "pleasure center". Teach a rat to press a switch that gives a minute electrical prod to the "pleasure center" and the animal will press the switch almost continuously-preferring the stimulation even to food. Given time, it could die of starvation-presumably happily. If you ever suffer a severe depression, doctors might implant such an electrode in your brain. Little jolts of electricity could transform a depressed you into an ecstatic you.

I reside, of course, in a well-protected fortress. The skull is 5 mm thick at the top, and even thicker at the base. I am bathed in a watery fluid that cushions me from shock. A blood-brain barrier serves as a gatekeeper, letting some things in, denying entrance to others. Thus, it welcomes the glucose I need, but blocks out bacteria and toxic substance. Most painkillers and anesthetics pass in with ease-but so, unfortunately, do alcohol and hallucinogenic drugs that wildly distort my normal activities. I may even "hear" a visual image.

A word about my architecture. Lift a piece of soil from a lawn and note the baffling intertwining of roots. I am something like that-multiplied by millions. Each of my 30 billion nerve cells, or neurons, connects with others-some as many as 60,000 times!

A neuron looks something like a spider attached to a filament. The spider is the cell body, the filament the axon, the legs the dendrites. The legs pick up a signal from adjacent neurons, pass it to the body; the signal is in turn passed along by the filament at speeds up to 400 kilo meters per hour. After each signal passes, it takes the filament about 1/2000 of a second to recharge itself chemically. At no point does one of my neurons touch another; signals are passed spark-gap fashion. At each "firing" one nerve chemically communicates with another.

For all my versatility, I unfortunately never learned the wonders of reproduction. Skin, liver tissue, blood cells can be replaced after damage or loss. But if I lose one of my cells it is lost forever-and by age 35, you where losing over 1000 of my nerve cells a day! With age, I also lose weight. But for my great reserves, these things might be disastrous. But I compensate. Let a thousand cells die and a thousand others may never notice the loss.

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