David takes a look inside the brain.
Segment length: 8:45
- What's going on in our heads?
- What are neurons and how do they send
messages to one another?
- Do our brains actually change when we learn something new?
Imagine what your own brain looks like inside your head. It is
pinkish gray on the outside, yellowish white on the inside, and
covered with ripples or convolutions. The brain has a delicate
consistency, like soft ice cream, and requires the shell-like
skull to protect it from injury.
Although it may not seem like it, you have just performed an
amazing feat. You have used your brain to think about itself.
As far as we know, human beings are the only animals on Earth
who can contemplate their own brains.
If you take a close look at a human brain, you'll find it has
three main parts. By far, the largest is the cerebrum
on top. The intricate surface of the cerebrum is called the cerebral cortex. Although only 0.3 centimeters (1/8") thick,
the cerebral cortex is critical to your ability to move as you please, to
understand what you see and hear, and to do the complex process
called thinking--making decisions, learning, analyzing,
remembering, planning, and contemplating.
Your cerebrum is divided into two halves. Each has specialized
functions. An "electric highway" of nerve fibers, the corpus
callosum, connects the two, allowing information to pass between.
At the back of your brain and beneath the cerebral cortex is
the cerebellum. It coordinates
skilled movement, giving you the ability to juggle, dance,
type, walk without stumbling, and drink without slobbering.
Located at the base of the brain is the brain stem, a stalklike
structure that connects it to the spinal cord. The brain stem
takes care of basic, involuntary functions, such as breathing,
blinking, and keeping your intestines churning.
Every part of the human brain is made of billions of nerve cells
called neurons. Each neuron has connections to thousands of other
neurons. For you to read this (or even to daydream), millions of
your neurons must communicate with one another.
A neuron accepts signals from other neurons through branchlike
structures called dendrites.
Whenever enough messages arrive from neighboring neurons to
excite it, a neuron sends an electrical impulse down its trunklike
axon. When the impulse arrives at the
end of the axon, it causes little sacs to release chemical
messengers. These chemicals, called neurotransmitters
, then travel across tiny gaps called synapses
to arrive at and excite other neurons.
When you learn something new, your neurons actually grow more
dendrites to reach other neurons. The more you practice, the
stronger these connections become. With 100 trillion possible
connections, your brain is one of the most complex regions in the
- When are you most aware of your brain in action? Which parts of your brain do you think are active when you
- What does information overload feel like? When, if ever, has it happened to you?
- Do you think your brain is similar to a computer? Why do some researchers
compare a single neuron in the brain to a computer?
axon the long tail at the end of each
neuron along which messages to other neurons are transmitted
cerebellum "small brain." The
part of the brain that coordinates movements.
cerebellum cortex the
rippled or convoluted surface of the cerebrum
cerebrum the largest part of the
human brain, primarily responsible for voluntary movement,
thought, and language
dendrites branchlike endings on
each neuron that receive incoming messages from other neurons
chemicals that convey messages from one neuron to another
synapse tiny space across which
one neuron communicates to another neuron
- Dennett, D. (1991) Consciousness explained. Boston: Little,
Brown and Company.
- Diamond, M. Within the human brain. (videotape). University
of California Extension Center for Media. Available through
Lawrence Hall of Science store, Berkeley: (510) 642-1929.
- Experiments in human physiology. Grades 7 and up. Apple IIs
with a minimum of 48K. Queue, Inc.: (800) 232-2224
- Mind and brain. (1993) Alexandria, VA: Time-Life Books.
- The mystifying mind. (1991) Morristown, NJ: Time-Life Books.
- Restak, R.M. (1994) Receptors. New York: Bantam Books.
- Stein, S. (1992) The body book. New York: Workman Publishing.
- Willensky, D. (1993, Dec) The brain. American Health, p. 78.
- Stark, F. (1991) Gray's anatomy: A fact-filled coloring book.
Philadelphia: Running Press.
Additional sources of information
National Foundation for Brain Research
1250 24th St. NW, Suite 300
Washington, DC 20037
Local MRI laboratory
University medical school
Santiago Ramon y Cajal, a Spanish artist and neuroscientist, was
the first person to figure out what a neuron looks like. Using a
cell-staining substance called silver salts, he was able to
observe and draw the intricate patterns of neurons in the brain
and spinal cord. Through his research, he concluded that synapses
provide the means for communication between nerve cells. In 1906
he won the Nobel Prize for his work. Use artistic and research
skills to create your own model of a neuron.
An assortment of construction or modeling materials, such as:
- felt-tip markers
- paper cups and plates
- Ping-Pong balls
- plastic tubes
- plastic wrap
- sculpting clay
- small squeeze bottles
- Research: Working alone or with a partner, investigate
what a neuron looks like and what it does. What aspect of the
neuron interests you the most? Find the images and descriptions
that you think illustrate it best.
- Initial plans: Decide what form you want your model to take.
As you design your model, emphasize the features that you find
most interesting or important. If you are collaborating with
someone else, discuss your ideas with one another. Sketch out what
you want your neuron model to look like.
- Building: Use the materials you find most appropriate and
begin building. If you get frustrated, take a break to look around
at what others are doing, and then come back to your work in
progress. If a certain material doesn't do what you would like,
try another. Work with your model until you feel it represents the
basic structure and ideas you want it to represent.
- Extending the model: If you haven't already, try extending
your model to include neurotransmitters, both those that excite
and those that inhibit another neuron from firing. Have several
students "connect" their models together to show how neurons
communicate as a neural network. How would you represent the
stimulating effect of caffeine?
- Do you think your model might help someone understand a
neuron better? What aspects does it illustrate well? Is it more
concerned with how the neuron looks or with how it works?
- How does your model differ from other models or drawings?
- What might you do to improve your model?
Hold your hand as far as you can above your head and drop a piece
of paper. Try to catch it as it flutters to the grounds. Now
try dropping a ball from the same height. Why is the piece of
paper harder to catch? (Adapted from Blood and Guts by L. Allison
[Boston: Little, Brown and Company, 1976], p. 117.)
As you learn, new connections are made between neurons. Choose
something new you would like to learn, such as juggling,
memorizing a poem, or speaking another language. Keep a journal
in which you describe your learning process. What challenges do
you encounter? When do you notice progress? How much time does it
take to learn something so that you don't forget it?
Research a disease or injury that affects brain function, such as
epilepsy, Alzheimer's, or Parkinson's. How does it affect the
brain? What symptoms does a person with this problem display? Are
there treatments for it? What causes it? What does this disease
reveal about how the human brain works?
For a day, try doing as much as possible with the opposite hand
that you normally use. Which tasks are particularly difficult? Do
you think this is similar to the challenge young children have
learning new actions, such as how to tie their shoes or pour
juice into a glass?
Newton's Apple is a production of KTCA Twin Cities Public
Television. Made possible by a grant from 3M. Educational
materials developed with the National Science Teachers Association.