show #1203

David takes a look inside the brain. Segment length: 8:45


Insights & Connections



Main Activity

Try this


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 universe.


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

neurotransmitters chemicals that convey messages from one neuron to another

synapse tiny space across which one neuron communicates to another neuron


Additional sources of information

National Foundation for Brain Research 1250 24th St. NW, Suite 300 Washington, DC 20037

Community resources

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:

  1. 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.
  2. 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.
  3. 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.
  4. 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?


  1. 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?
  2. How does your model differ from other models or drawings?
  3. 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.