“The Wave” – Neuron Action Potential Propagation

Some of our most popular blog posts describe teaching tips developed by HAPS members. We choose a handful of these to publish on the blog, but there are hundreds of tips that have been collected over the years. These little snippets are being linked to the HAPS A&P learning outcomes and posted to the HAPS website, for members only. So join HAPS now, and get access to many more teaching tips like this one.

Enjoy this teaching tip from HAPS Past President, Terry Thompson.

Objectives:

1. Engage students with a kinesthetic demonstration of the action potential “wave” with ions moving in or out of membrane channels
2. Generate visual memory tools to help students’ learning and long-term understanding
3. Motivate critical thinking by having students analyze and evaluate various components of the activity as a model of the physiological events

Materials:

• Color-coded cards: multiple cards with Na⁺/K⁺ on opposite sides; one card with ACh/Ca²⁺ on opposite sides; one card with neuron cell body/synaptic end bulb on opposite sides. Can use cardstock or plastic protective sleeves. Use large font to fill single page.

 Procedure:

1. Line students up facing class (or each other if using two lines). Explain that students will represent the axolemma: phosphate “head”, lipid “legs”, voltage-gated channels “arms”.
2. Give each student a Na⁺/K⁺ card and review relative concentration of each ion extracellular and intracellular. Designate: above “heads” as extracellular and floor as intracellular; right hand as voltage-gated Na⁺ channel and left hand as voltage-gated K⁺ channel. Start with Na⁺ card held toward observers, above their heads, in right hand.
3. Demonstrate the depolarization/repolarization cycle by bringing Na⁺ card down in front of body, flipping K⁺ side toward observers as pass to left hand, then move above head.  Have all the students practice this synchronously until they feel comfortable, saying “depolarize” and “repolarize” out loud to help.  Discuss the electrogenic activity of the Na⁺/K⁺-ATPase pump as it relates to this kinesthetic demonstration.
4. Review continuous conduction and challenge them to now complete the same movements but this time in sequence, like the “wave” in a stadium.  Show the “neuron cell body” and “ACh” cards and discuss what initiates the impulse.  Can elaborate on difference between ligand-gated and voltage-gated channels; graded potential, threshold, and action potential; neurotransmitter for motor neuron or other neurons; dendrites, soma and axon hillock; etc.  Students will often come up with ideas of ways you could include other elements in the demonstration, or at least evaluate and understand what this particular activity as a model is NOT showing.
5. “Start” the first person in line by saying “threshold”, and allow the “wave” to progress down the axon.  This usually elicits lots of laughing and suggestions from the audience.  Allow them to repeat until they produce a reasonable “wave”, starting each with a threshold stimulus.
6. Finally as a reasonable “wave” is progressing down the line, run to the other end and flip your cards to show synaptic end bulb and hold the Ca²⁺ card above your head.  When the wave reaches you, bring the Ca²⁺ down and flip to ACh, passing it above your head for release of neurotransmitter at synapse with muscle or another neuron.  Discuss this added activity to the model as a way to summarize the activity.
7. Extensions can include discussing what parts of this demonstration could be improved on or don’t accurately reflect the physiology.  Can also discuss what would need to be changed to demonstrate saltatory conduction instead of continuous conduction.

NOTE: This activity was also presented by Terry Thompson at 2016 HAPS Atlanta Conference as part of the group workshop entitled “Add Drama to Your Classroom – Great Kinesthetic Activities for Students.”