• Students will construct an accurate model of several neurons sending and receiving signals.
• Students will be able to describe the function of a neuron and its role in the nervous system.

Students will understand how neurons and supporting cells allow electrical signals to flow throughout the central nervous system.

Teacher Preparation

Print out the What’s In a Brain? lab notebook. Gather the materials to build the potato circuit:

• Two potatoes
• One low voltage light bulb
• Two pennies
• Two galvanized screws or strips of zinc
• Three alligator clips

The students can do this project individually or in pairs. To increase the difficulty of the task, try adding other fruits, vegetables, uncoated wire or coins into the mix.

Hands-on Activities
Build a Brain Activity
Students will problem solve to create a brain circuit using potatoes, wire, pennies, screws and a lightbulb.

Action Potential Secret Code
Students will use their axons (left hand) and dendrites (right hand) to send a secret tapping code around the classroom. The teacher will be the first and last neuron. The timer will start when the signal is sent and stop when the correct “message” is received by the teacher. Students will have their eyes closed with one palm up on the dendrite side (right) and their finger touching the open palm of the person next to them on the axon side (left).

Lesson Plan

Day 1
Introduction (slides 1-2) (5 minutes)
Using the What’s In a Brain? More Than Matter! slideshow and the Glowing Green video, have students answer the questions. Students might notice the glowing and guess that it is some kind of animal or bacteria. You will return to this at the end, so pay special attention to their initial thoughts.

Slides 3-4
What is the brain’s job? (5 minutes)
Discuss how complex the brain is with all its neurons working together to perform a single function.

Slides 5-14
What is a neuron? (15 minutes)
Progress through slides 5-11. Discuss the units of the brain and what makes up a neuron. When you reach slide 9, discuss how a neurotransmitter is made. While this guide makes it seem like neurotransmitters are synthesized in the nucleus and moved down to the dendrite, most neurotransmitters are recycled rather than making entire new molecules (slides 9-10).

The point of these slides is to show students how organelles are involved in making neurotransmitters. It’s also important to note that each of the 200+ neurotransmitters is not made through the same process. You will end this section by looking at an electron microscopy image of a neuron (slide 11). In the image, students can see what neurons look like up close.

Slides 15-17
Glial cells (5 minutes)
Glial cells are not a part of either activity. However, they are just as important as neurons in the brain. Students should understand that glial cells come in many shapes and sizes and accomplish a wide variety of jobs in the brain. The first example (slide 12) is of astrocytes. These cells act like glue to hold neurons in place in the brain. Another job of the glial cells is to help with learning.

Students who are familiar with mitosis might be surprised to find out that neurons do not undergo this type of cell division.

Slides 18-19
Brain signaling secret code activity (5 minutes)
After showing students an example neurotransmitter (dopamine), students will try sending their own signal. Students will use their axons (left hand) and dendrites (right hand) to send a secret tapping code around the classroom. The teacher will be the first and last neuron. The timer will start when the signal is sent and stop when the correct “message” is received by the teacher. Students will have their eyes closed with one palm up on the dendrite side (right) and their finger touching the open palm of the person next to them on the axon side (left). You can make this a competition by splitting the class into two groups or having different classes compare times.

Day 2
Slides 20-21
How do neurons send signals? (5 minutes)
After the exercise, students will think about the scenario (slide 15). The goal of this think-pair-share is to have students conclude that electricity is the best way for the brain to send signals. However, students may believe neurotransmitters are the only way the brain can send signals, so you may need to guide their thinking. It is also important to note that this electricity is actually an electrochemical gradient. This means that there are more positively charged ions on one side of the membrane than on the other, which causes an energy potential. When neurotransmitters bind to the dendrites the electric signal is released. To explain this to students, use an example of static electricity building up before being released when you touch something. You can also use the example of lightning. In a lightning storm, positively-charged particles build up in clouds before being released in an explosion of energy.

Slides 22-23
Build a Brain Activity (20 minutes)
In this activity, students use generic supplies to build a potato-powered lightbulb. The goal is for students to build a model of neurons (potatoes) working together to send a signal. If you find the initial model too simple, you can add complexity by adding other fruits, vegetables, uncoated wire or coins. After students have successfully illuminated their lightbulb, ask them to reflect on what each piece of their model represents, if there are neurotransmitters or myelination in the model, and how the structure of a neuron affects its function.

Answers:

• Potatoes = neurons
• Light bulb = eyes (or any organ receiving or sending signals to the brain)
• Pennies = synapse
• Galvanized screws = synapse
• Alligator clips = dendrites/axons

If students are really creative, they could say there are neurotransmitters in two ways. First, there are electrolytes in the potato that allow the electricity to flow. Second, since the penny and screws are not touching there would need to be something to carry the signal across the synapse. The myelination in the model is the coating on the wires.

The final question has students think about two parts of the model. First, what is the function of a neuron? Second, what structural features are there to help a neuron accomplish said function? The function of a neuron is to send and receive signals. Neurons have myelination and use electricity to help them accomplish their function more efficiently.

Slides 24-28
Stem cells and conclusion (10 minutes)
Stem cells are undifferentiated so they can become any cell type. Scientists use different types of solutions to trigger these cells to become a particular type. To learn more about making stem cells, watch the Inside the Lab with a Kid Scientist video.

Students will consider the pros and cons of growing cells in a dish (slide 21). Some possible discussion topics include:

• Pros: You can test drugs or create models of diseases. Animals do not need to be used for research.
• Cons: Reprogramming the cells can make them cancerous. Cells growing in a dish cannot simulate all the variables present in the body.

For a more in-depth look at medical ethics, see the Medical Ethics: Right, Wrong and the Space Between lesson.

Students will come back to the Glowing Green video from the beginning of the presentation. Hopefully, they now see neurons firing. The clip actually shows calcium being released, which is an indicator of neurons firing.

The Sanford Connection

At Sanford Research, scientists use stem cells to create models of diseases. They not only use stem cells for studying the brain, but they also study countless other systems and models. The stem cell models allow scientists to study diseases without using as many animal models.

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