See Your Own Action Potentials
Meet my muscle action potentials. Action potentials are the changes in the charge of the inner and outer membrane of your muscle fibers which allow your muscles to contract. And for only around $80, you can see yours too! Here’s how, but first, a little background.
In the milliseconds it takes to contract your muscles, your brain orchestrates a series of events that allow you to contract your muscles. First, neurons in the motor cortex of the brain, which extend along your spinal cord, synapse, or make a connection, with lower motor neurons in the spinal cord. These motor neurons then synapse with muscle fibers and fire an action potential which causes the release of the neurotransmitter acetylcholine into the synapse (“Synapse” can be used as a verb or noun: “to synapse” is to make a connection and a “synapse” is the junction between two neurons or a neuron and a muscle fiber). The acetylcholine causes a change in the charge of the inner and outer membranes of the muscle fiber and can cause it to make its own action potential (if a certain threshold is met), resulting in a twitch. Many muscle twitches result in a muscle contraction. Since all of this is just electricity, you can look at your own action potentials using what is known as a bioamplifier.
This lab is heavily inspired by the Backyard Brains “Getting started with the EMG SpikerBox” lab. However, instead of using the Backyard Brains SpikerBox bundle, I found a cheaper alternative: a combination of an Arduino Uno and an Olimex EMG shield which work together as a bioamplifier.
More detailed theory for this lab can be found under the "background" heading in the Backyard Brains EMG SpikerBox lab.
3 Electrode cables ( I made my own by soldering 3 alligator clip test lead cables to a 3.5mm plug, but you can purchase ready made cables from the link if you prefer)
For information on how to set up your arduino uno and download its drivers, visit the arduino website.
You can find all the Olimex EMG shield user guide, arduino EMG code, and download the Electric guru software from the Olimex EMG shield website.
1. Set up your arduino and download its drivers. The arduino will recieve electrical information from your muscles through the EMG shield and electrodes. And using the code, you will be able to see your own actual action potentials in a program called Electric guru.
2. Download the Electric guru program.
3. Download the arduino EMG code (it’s labeled as EKG but it also works for EMG).
1. Attach the muscle shield to the arduino (they fit on top of each other) and connect the arduino to your computer using a usb cable.
2. Place 2 electrode patches on your biceps (upper arm). One towards the top of your biceps and the other towards the bottom. You need these two electrode patches because the EMG recordings display the potential difference between two seperate electrodes.
3. Place the third electrode on your elbow. This will serve as the ground, or reference electrode.
4. Connect each electrode patch to an electrode cable and connect the cable to the muscle shield.
5. Connect the arduino to your computer and start up the Electric Guru program.
6. Once you have opened up the program, go to preferences -> Trace and make sure that both channels are on because the program will display the result from the potential difference between the two electrodes on you biceps.
7. Click start. You should see straight, slightly squiggly lines. But once you contract your muscles, you should see the muscle spikes because your muscle contractions result from action potentials. Keep in mind that since the electrodes are reading from your biceps, the muscle spikes you see are from 100s of muscle fibers, because the biceps contain many muscle fibers.
Congratulations! You have just seen your own muscle spikes.