The nervous system is capable of transmitting signals nearly instantaneously. Nerves make use of action potentials to relay signals rapidly. Action potentials are electrical in nature, and they can be measured.
Action potentials traveling through your nerves are responsible for the sensations you feel every day. For example, if you touch a hot cup of coffee, your hand automatically jerks away from the cup. This is called a reflex, and it is controlled by several action potentials traveling from the skin of your fingers to the spinal cord and back. The response is instantaneous, and you don’t even have to think about it.
Action potentials are the driving force behind your nervous system. Without them, you would not be able to sense anything.
Learning action potentials gives your students a better appreciation of how their bodies work. Measuring the electrical activity of nerves is possible, though the process is not quite straightforward. Both the theory and practical knowledge of action potentials can be a huge challenge for students.
Students often lose interest in science topics like action potential because they tend to be complicated. Here are the top three factors that make this topic a tricky one.
There is no way to see an electric current moving through a nerve. The only way to ‘see’ it is to measure the voltage or current of the nerve. The changes in the readings of the voltmeter or ammeter provide the best visual representation of an action potential.
Determining the electrical activity of nerves is a meticulous process. For one, nerves are so thin and fragile, making it hard to manipulate them. The slightest misstep can break a nerve fibre, rendering it useless.
Electricity present in nerves is also minute, making it a challenge to measure. It takes highly sensitive instruments to measure tiny quantities of current and voltage.
Voltage and current are abstract concepts in physics. The only way to visualize them is through measurements. Action potentials both involve voltage and current, so students may not be able to appreciate the concept right away.
Combined with the intricacy of the nervous system, action potentials can be a daunting topic altogether for students.
If you want your students to gain a better appreciation of this topic, there are ways to make them interested.
Image source: Wikimedia Commons
While action potential can be a tricky topic for university students, it remains essential for their study of biology. To get your students interested about this topic, here are five tips.
The action potential was discovered through a collaboration of two scientists. In 1939, Alan Hodgkin and Andrew Huxley devised a method to measure the action potential propagating through a nerve.
Hodgkin and Huxley were able to get around the difficulty of manipulating nerves by using a giant axon from a squid. With the help of special microelectrodes, they were able to measure the membrane potential of the squid giant axon. Also, they were able to track the depolarization and hyperpolarization processes that compose the action potential.
They received the Nobel prize in Physiology and Medicine in 1963 for their work.
IImage source: Wikimedia Commons
Action potentials involve concepts like voltage, otherwise known as electrical potential. That’s where the “potential” part of the action potential comes from. Basically, an action potential is a change in voltage in nerve cells.
It helps to review these fundamental concepts when introducing action potential to students:
Voltage. This is the difference in electrical potential energy between two points. Voltage can also be thought of as “pressure” but in electrical terms.
Ions. Ions are molecules that are either positively or negatively charged. Potassium and sodium ions, which are key elements in action potentials, are both positively charged ions.
Axon. The long, threadlike part of a nerve cell that transmits signals to neighboring nerve cells.
Neuron. Another name for cells of the nervous system responsible for transmitting and receiving signals.
Electrode. A device inserted into axons used to measure electrical activity.
Membrane potential. A membrane potential is the difference in electrical potential (in millivolts or mV) between the outside and inside of a cell's membrane, on the intracellular side of the membrane based on the outside being zero.
Resting potential. Different types of cells have different resting membrane potentials. The resting membrane potential of neurons is -70 mV. During action potentials, the membrane potential changes drastically.
Ion channels. Ion channels are membrane proteins that form a pore which allows ions to pass through. In neurons, there are two main ion channels called voltage-gated sodium channels and voltage-gated potassium channels.
Voltage-gated sodium channel. These are proteins that actively transport sodium ions from one side of the membrane of a neuron to the other, changing the membrane potential of the neuron. The transport of sodium ions is driven by changes in membrane voltage.
Voltage-gated potassium channel. These are proteins that actively transport potassium ions from one side of the membrane of a neuron to the other, changing the membrane potential of the neuron. The transport of potassium ions is driven by changes in membrane voltage.
Depolarization. A change in membrane potential of a neuron from its resting potential of -70mV to a highly positive value.
Repolarization. The return of a neuron’s membrane potential from a highly positive value to a negative one.
Hyperpolarization. A decrease in a neuron’s membrane potential that goes below the resting potential of -70mV.
Stimulus (plural: Stimuli). Changes in the environment that are detected by neurons. Stimuli can trigger action potentials.
Students gain a much greater appreciation of abstract concepts like action potential when they can see what’s going on. Interactive simulations like the one pictured below from Labster make action potential a more fun topic to learn.
The image below depicts a snippet taken from Labster's Action Potential Lab: Experiment with a squid neuron Virtual Lab showing how action potentials are measured.
Mnemonics and wordplay are great tools for students when studying complex topics like action potential. In particular, the progression of the action potential has some terms that are difficult to remember.
In particular, creative words are useful in remembering the different stages of an action potential. For instance:
LEAP into Action!
L: less negative
AP: action potential
In other words, when the membrane potential becomes less negative (or more positive), the neuron is excited, which leads to an action potential. When the neuron returns to a negative membrane potential, it goes back to its resting state.
A virtual laboratory simulation is a great way to teach action potential. At Labster, we're dedicated to delivering fully interactive advanced laboratory simulations that utilize gamification elements like storytelling and scoring systems inside an immersive and engaging 3D universe.
Check out simulations of an Action Potential experiment at Labster. After learning all about it, your students can be more confident when they will do it on their own in a real lab! The image below is an example of what students can explore in the simulation.
Please take a look at the following image from Labster's Action Potential Lab: Experiment with a squid neuron Virtual Lab or get in touch to find out how you can start using virtual labs with your students.
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