Instructions: Please read the text and answer the questions below.

Chapter 9 text

UNLOCKING THE SECRETS OF NEURONS

The brain is composed by seventy five percent of water and weighs about one point three kilo, or two percent of our total body weight. It emits one billion signals per second and contains fifty percent of the body’s genes. The nervous system developed six hundred million years ago and consists of one hundred billion neurons.

Understanding and treating nervous system disorders has become one of the major challenges of the twenty-first century. Neurological disorders affect over a billion people worldwide – degenerative illnesses associated with aging (Alzheimer’s, Parkinson’s), cerebral accidents, epilepsy, multiple sclerosis, and psychiatric disorders (depression, schizophrenia), among others. Scientists are beginning to comprehend how the brain functions, and therefore how it dysfunctions. In ten years they have made tremendous progress.

However, despite the extensive research devoted to the brain, many questions remain unanswered: How do we think? What is the purpose of sleep? Why are we happy or unhappy? The objective of twenty-first-century brain research is to prevent, repair and heal the nervous system.