Experiment: Record and Manipulate Live Neurons!
Did you just get a SpikerBox, and are wondering how to use it? In this lesson, you will listen to action potentials and view "spikes" in real time. This is an excellent starting point for your SpikerBox as well as a great nervous system lab for students as young as middle school! See live action potentials in an engaging lab activity!
What will you learn?
This is THE experiment to get you started with neuron spikes! By the end of this experiment, you will understand what neurons are, how they communicate, the principle of rate coding, and how to record spikes using a SpikerBox!
- Caring for Cockroaches - If you are new to insect husbandry, the bottom of our cockroach product page has tips for maintaining a healthy colony.
Your brain uses a combination of chemicals and electricity to operate. Brain cells (neurons) communicate with each other to control your body. A brain with only 1 neuron is not a brain.
A brain is a network (friendship) of neurons. Your brain has and uses around eighty billion neurons! But how do all of these neurons talk to each other? One of the first ways cells used to network was chemical communication.
Bacteria use this method. It works well, but is limited by diffusion. For example, when you release an odor on one side of the room, how long does it take for someone on the edge of the room to smell it? There should be a faster way. One way is to bring cells closer together through stretching.
But there is still a problem. The signal still needs to travel a long way through the cell. Is there a way to make this faster? What is very fast and important today?
Electricity! Notice how fast the lights in your house turn on when you flick the switch. Neurons use electricity as well; electrical pulses travel down the neurons. This pulse is called the:
We at Backyard Brains have dedicated our lives to studying spikes (also known as action potentials), and you can too! What shall we use to study neurons? 380 million years of evolution bring you the cockroach. That's even older than dinosaurs! We will use the Discoid cockroach (Blaberus discoidalis), or false death's head. They live in the Amazon rainforest of South America under the bark of rotting trees.
Like most multicellular animals (beyond creatures like sea sponges), cockroaches' bodies are filled with nerves (which are bundles of neurons) to control movement & sensation. As said above, neurons use a combination of electrical and chemical signaling to function.
How does the neuron generate the electrical impulse? It is due to both a chemical and electrical difference across the inside and outside of the neural membrane.
The movement of sodium and potassium across the neural membrane causes the momentary change in voltage called the action potential or "spike".
What happens when the spike reaches the end of the axon? It causes the release of neurotransmitter across the synapse, which can change the electrical properties of the next neuron, making it more or less likely to fire a spike of its own.
Wow that's a lot of theory! And a lot of Nobel Prizes gained in the process! Now it's time to be students of action. We will try to measure spikes, using the very reliable cockroach leg preparation (don't worry, the cockroach leg can grow back). You will be an electrophysiologist!
On the cockroach, each thorn on each leg is innervated by a neuron:
Touching the thorns causes the neurons to fire spikes. With more force applied to the thorn, even more spikes occur. This relationship of spikes to stimulus strength is called "rate coding" and was first discovered in 1926 by Lord Edgar Adrian in England at the University of Cambridge (we will learn more about him later).
Now let's see this spike for real!
Before you begin, make sure you have the Backyard Brains Spike Recorder installed on your computer/smartphone/tablet. The Backyard Brains Spike Recorder program allows you to visualize and save the data on your computer when doing experiments. We have also built a simple lab handout to help you tabulate your data. You can also download the illustrations in the experiment in a powerpoint file.