Electricity in Our Bodies

What you'll need

• Computer and projector or TV
• “Electricity in our bodies” slideshow
• Video: https://www.youtube.com/watch?v=6qS83wD29PY
• “EMG Experiment worksheet”, print one copy per group of 3-4 students
• Group experiment supplies, plan for 3-4 students per group
• Laptop or tablet and internet connection (we suggest using Google Chrome for the browser)
• Micro:bit and connection cable (you can reach out to us for help sourcing micro:bit lending kits in your region)
• 2 alligator clips
• Aluminum foil: fold 2 pieces into squares approximately 4cm x 4 cm
• Tape

Introduction

1. Start the activity by having a class discussion on how electricity works to powers our lights and devices and/or do the activity “Tic Tac Flow: How we Generate Hydroelectricity”
   • Electricity that powers the lights is the flow of electrons through a metal wire. They flow/are driven by a voltage difference that creates an electric current. This is then transmitted over long distances to be used to power lights and devices. The voltages in power lines are high and measured in kilovolts (kV).
2. Ask students if they have ever heard that, like transmission lines, our bodies function by transmitting electrical signals. The voltages however are significantly lower and are measured in millivolts (mV).  

Electricity in Human Cells

1. Pull up the “Electricity in our bodies” slideshow 
2. Slide 2 - Share with learners that in their bodies they have cell-based electricity. The flow of positively and negatively charged ions like potassium and calcium across cell membranes creates electrical currents that enable everything from their heart to beat to their brain to think. Their bodies have a nervous system that acts as the body's communication network, sensing the environment and processing information. 
3. Slide 3 - Share that the nervous system is made up of neurons that allow the body to communicate rapidly and precisely. Ask students what type of message might be communicated in our bodies? 
   1. They may have ideas like if they touch something hot a message might be sent to their brain, and in turn the brain sends the signal back to their muscles to remove their hands. 
4. Slide 4 - Ask learners to consider electricity in transmission lines. What do electrons do? They cause electricity to flow through the metal transmission wires. Share that electricity in the body is cell-based. The cells use electrical signals to operate and flow through the body.
5. Slide 5 – Share with learners that their bodies contain billions of neurons, and their brains also contain about 86 billion neurons all connected. 
6. Slide 6 - Show students the diagram of a typical neuron. 
   1. The tree like dendrites receive signals from other neurons via a chemical messenger (ions) called neurotransmitters. 
   2. The signals cause electrical changes in neurons that are interpreted in the cell body. 
   3. If the signal is strong enough messages are sent down the axon. This signal is called an action potential.
7. Slide 7 – Explain to learners that the axon is covered with myelin, an insulator which prevents degrading of the signal. 
   1. With student input, compare this to an electrical insulator in their homes: An insulator is a material that resists the flow of electric current. An example would be the plastic coating around electrical cords. 
   2. The signal then moves to the axon terminal, where the release of neurotransmitters interacts with receptors on the next neuron sending the signal through the body.
8. Slide 8 - Share that the cell membrane is the outer layer of the entire neuron and the voltage difference is measured in mV and typically is about -40 to -70 mV. Conversely for electricity transmission lines the voltages are magnitudes higher 60kV to 500kV.
   1. To check understanding, ask students if this means the inside of the neuron is negative or positive and why that might be. (It’s negative because more negatively charged ions, like Cl, are inside and more positively charged ions, like Na and K are outside)
9. Slides 9 & 10 - Show & explain the two types of neurons: sensory and motor.
   1. Sensory neurons carry incoming information from the sensory receptors of the body towards the brain, for example when they touch something hot.
   2. Motor neurons carry information from the brain back to the muscles, for example to signal to our muscles to move their hand away from something hot.
10. Slide 11 – Show learners video to summarize the learning. 

Electromyography (EMG) Experiment

1. lide 12 - Ask learners if they know what an electromyography (EMG) test is. This is a test that measures the electrical signals muscles produce at rest and during contraction to check for nerve or muscle activity.
2. Explain to the students that they will now do their own version of an EMG. Provide each student with a copy of “EMG experiment worksheet”. 
3. Put students in groups of 3-4 students and provide each group with the experiment supplies: laptop or tablet, Micro:bit and connection cable, 2 alligator clips, 2 pieces of aluminum foil folded into squares approximately 4cm x 4 cm and tape.
4. Have students follow the experiment instructions on the screen working together as a class or in individual groups using the worksheet. 
5. Once all students have conducted the test have a class discussion on each group’s results.