BRAIN

The largest organ in the nervous system is the brain. It controls vital involuntary processes, such as breathing, as well as our thoughts, emotions, memories, and sensations. Brain scans can monitor brain activity, called BRAINWAVES.

WHY IS THE HUMAN BRAIN SPECIAL?

Relative to body weight, the human brain is the largest in the animal kingdom. Its surface, the cerebral cortex, is also the wrinkliest. During human evolution, the cerebral cortex grew, and so became wrinklier to fit inside the skull. The large cortex, site of unique abilities such as language, is probably what makes humans unusually intelligent.

WHAT IS THE BRAIN MADE OF?

The brain contains more than 100 billion neurons and a multitude of helper cells, which nourish and support the neurons. The cells are organized into different areas, the largest of which is the cerebrum. The whole brain is surrounded by protective membranes and cushioned by fluid-filled hollows.

HOW DOES THE BRAIN WORK?

Scientists used to think that each part of the cerebral cortex carried out a specific function. Recent research has shown the brain to be more complicated. During speech, for instance, large areas of the cerebral cortex work together in an ever-changing pattern.

BRAINWAVES

Doctors can monitor a person’s brain by looking at brainwaves, the pattern of electrical activity produced by all the brain’s neurons. There are three main types of wave: alpha, beta, and delta. They are detected by an EEG (electroencephalograph).

IS THE BRAIN ACTIVE WHEN WE SLEEP?

The brain is always active, but the level of activity varies. In deep sleep, when delta waves occur, the brain is working but at its least active. During dreams, the eyes dart around, and the brain produces alpha waves and is just as active as during waking hours.

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Nervous System
Skeleton

Copyright © 2007 Dorling Kindersley