Page 39 - Mind Games The Aging Brain and How to Keep it Healthy

The Intelligent Mind • 23

GENERAL DEVELOPMENT OF THE BRAIN

Let’s get started. Pictures of the brain are all around us in
newspapers, magazines, and on television. Therefore, you
probably already have a general idea of what the brain looks
like. We’re going to probe deeply into the structure of the
brain so that you will know precisely why we want you to
practice certain strategies and techniques and exactly what
is happening as you reinforce your mental agility. Let’s start
with some of the vocabulary and imagery needed to talk
about and visualize brain structure.

neuron—nerve cell in the brain

The neuron is the basis of the brain. It is estimated that
the brain contains 100 billion neurons, which is roughly
equivalent to the number of stars in the Milky Way galaxy. 2
Each neuron is a nerve cell composed of a center, named the
nucleus, with long, slender axons and short, bristly dendrites.

axon—messenger of the brain
dendrite—message receiver in the brain

Neurons communicate with each other by passing nerve
impulses down the axon of one neuron. At the end of each
axon is a minute gap called the synapse

synapse—gap between axon and dendrites

As the nerve impulse reaches the end of the axon, a
chemical, called a neurotransmitter, is released into the
synapse. On the other side of the synapse is a dendrite of an-
other cell that acts as the receiver for the signal.

neurotransmitter—a chemical released by the axon to
send and store messages across a synapse

In Figure 2-1, you can see the path the message follows
from one neuron to another. This message travels from one