One of the most difficult concepts for my students to grasp during Project Lead the Way’s Human Body Systems course is the concept of an action potential. Before learning about action potentials, we do some basics with neuron structure. Students start by putting together a puzzle of a neuron and coloring it. I then take the 3 best colored/labeled neurons and we hang them on the wall, connecting them to represent a sensory neuron, interneuron and motor neuron.
Students work in teams to make labeled 3-D models of a motor neuron and they research what the parts of a neuron do.
Once students have grasped the basics of neuron structure, they do some research to learn about action potentials. My favorite site to use is the Harvard Action Potentials Animation. Students should go through it slowly several times, taking careful notes. Below are my sample notes from my own interactive notebook. Students can make the 3 flap shutterfold by folding a piece of paper in half and cutting 3 flaps. I show students how to do that step. I allow students to CHECK their notes off mine, but they cannot view my Notes Journal until they complete their own notes.
I give each student a copy of the action potential summary table to fill out as well. I find that the table really helps them to process all of the information.
After laying the ground work, I want to give kids a kinesthetic experience with all that they’ve learned. I tried a couple activities from other people and ultimately synthesized them into my own. The one that I drew the most inspiration from was Pom Pom Potentials and it’s a great alternative to the one I came up with (and simpler to set up). For my activity, I wanted to physically add in the channels and pumps, so I took it a bit further. Below are my students completing this activity.
To do my activity you need the following materials:
- 6-8 pool noodles (for 24-32 students respectively)
- 6-8 orange Solo cups (substitute any color)
- 6-8 green Solo cups (substitute any color)
- 6-8 paper plates
- A hot glue gun
- A box cutter
- A Sharpie
- Duct tape
- 450 wooden blocks separated into a pile of 150 and a pile of 300
- Orange and Green spray paints (substitute any color, but make sure they match cups)
Here’s how to set it up.
- Use duct tape to show which is the “inside” and which is the “outside” of the membrane (pool noodles).
- Use the box cutter to cut an opening in the bottom of every cup. Make sure the opening is large enough to let your blocks pass through. You may want to leave the flap of plastic there so you can represent the channel opening and closing.
- Label all of your orange cups Na and glue them to the pool noodle with the arrow showing the the sodium ions will pass from the INSIDE to the OUTSIDE of the membrane. Glue one to each pool noodle.
- Label all of your green cups K and glue them to the pool noodle with the arrow showing the the potassium ions will pass from the OUTSIDE to the INSIDE of the membrane. Glue one to each pool noodle.
- Label each of your paper plates to show that 3 Na ions will pass to the OUTSIDE and 2 K ions will pass to the INSIDE. Glue one to each pool noodle.
- Spray paint 300 of your blocks orange to represent the sodium ions and 150 green to represent the potassium ions (if using a different color, make sure they match the cups).
- Lay out all of your pool noodles on the floor as shown below. The insides of the “membrane” should face each other. Put the sodium ions on the outside, spread evenly and the potassium ions on the inside, spread evenly. This represents the neuron at resting potential.
- Consider putting some “DNA” on the inside to help explain why the inside has a negative charge. In the pictures of my students, you’ll see 2 students standing inside the membrane holding boxes of DNA models for this purpose.
- Randomly assign 1/4 of the students to be potassium channels and have each claim a green cup and sit on the INSIDE of the membrane at their green cup.
- Randomly assign 1/4 of the students to be sodium channels and have each claim an orange cup and sit on the OUTSIDE of the membrane at their orange cup.
- Put the remaining half of your students in teams of 2. Each team will run a sodium potassium pump together. Have one student sit on each side of the pump. Give these students a small bag of candies (I gave them chocolate chips).
- Instruct the sodium potassium pump students that they MUST work together with their teammate. Every time there are 3 sodium ions inside and 2 outside, they need to lay them on the plate, push them to the other side of the membrane and eat a chocolate chip to represent ATP. They do this EVERY CHANCE THEY CAN.
- Have the students determine which end of this axon should be the dendrite end and then stand at that end. Instruct the sodium channel students NEAREST TO YOU to open the channels and start pushing sodium ions through (only the 2 students closest to you should do this). Students should count out loud as they push them through. When students reach 15, that’s the “thresh-hold” and should trigger the potassium channels next to them to open. Have those students start passing potassium ions out of the membrane. Remind the Na/K pump students to operate the pump ANY TIME THEY CAN. The picture above shows how the ion concentration will change as the action potential starts.
- As the potassium channels nearest you finish passing 15 potassium ions through, move down the axon to show the action potential moving.
- Have students switch roles and run the simulation again.
I found that while this activity helped them much better understand the channels and pump and how they work, they still struggled to connect all this to polarization and depolarization. In the future I’ll have us draw the graph of an action potential on our lab tables in chalk markers as we do each step and label the parts of the graph based on what happened.
I’d love to hear from you. How do YOU teach action potentials? What works for your kids? If you try this activity, please let me know if it worked for you. And if you have questions, please post them.