Teaching Action Potentials and Neurons to High School Students: A Simple Nervous System Guide

The nervous system is one of those biology topics that students often find fascinating, but also incredibly confusing. Terms like resting potential, action potential, and saltatory conduction can quickly overwhelm students if the concepts are introduced too quickly or without clear connections to basic chemistry and physics.

Over the past week, I found myself teaching the nervous system to several different students preparing for different exam boards; GCSE, A-Level, and IB Biology. Although the specifications varied slightly, the core ideas were the same: students needed to understand the types of neurons, how an action potential is generated, and how myelin speeds up nerve conduction.

After explaining the same concepts multiple times, I was reminded of a few simple teaching strategies that consistently help students grasp how nerve impulses actually work. In this article, I’ll share a few of the approaches and analogies I use when teaching the nervous system to high school biology students.

Start with the Big Picture: The Structure of the Nervous System

Before diving into action potentials and membrane potentials, students first need a clear overview of how the nervous system is organized.

Explain:

• Central Nervous System (CNS)

  • brain + spinal cord

  • processing center

  
  

• Peripheral Nervous System (PNS)

  • nerves carrying signals to and from the CNS

    
    

Then transition:

Once students understand the overall structure, it becomes much easier to explain how information actually travels through the system.

Introduce the Three Types of Neurons First

Explain:

Sensory neurons

• carry impulses from receptors to the CNS

  
  

Relay neurons

• located in the CNS

• connect sensory and motor pathways

  
  

Motor neurons

• carry impulses from the CNS to effectors

• muscles or glands

Then add a teaching tip:

A simple way to help students remember the order is to present the pathway as a flow of information:

Stimulus → Sensory neuron → Relay neuron → Motor neuron → Response

Help Students See the Chemistry Behind Nerve Impulses

One of the biggest breakthroughs for many students occurs when they realize that nerve impulses are not mysterious electrical signals, they are actually driven by basic chemistry and ion movement across membranes.

I often remind students that ions such as sodium (Na⁺) and potassium (K⁺) carry positive charges. When these ions move across the cell membrane, they change the electrical conditions inside the neuron.

Then explain:

Resting potential

• neuron is polarized

• inside is more negative than outside (approximately -70mV)

• maintained by ion distribution and sodium-potassium pumps

Teaching tip:

I often tell students to imagine the neuron membrane as a system trying to maintain a balance of charges, where different ions are constantly moving to keep the internal environment stable.

Explaining the Action Potential

You can start by explaining it in simple steps, but the key thing is to use the visuals alongside the steps:

1. Stimulus opens sodium channels

2. Sodium ions rush into the neuron

3. Inside becomes more positive (depolarization)

4. Potassium channels open

5. Potassium ions move out

6. Membrane returns to resting state

Students often find this easier to understand when they focus on the movement of charges, rather than memorizing the steps mechanically.

The Myelin Sheath and Saltatory Conduction

One of my favorite analogies when explaining myelin and nodes of Ranvier involves climbing stairs.

Imagine you are trying to move quickly up a staircase. Instead of stepping on every single step, you skip steps to reach the top faster.

Something very similar happens in myelinated neurons. The electrical signal does not travel continuously along the entire membrane. Instead, it jumps from one node of Ranvier to the next, dramatically increasing the speed of transmission.

This process is known as saltatory conduction, and it explains why myelinated neurons can transmit impulses much faster than unmyelinated ones.

Teaching Tips for the Nervous System

1. Start with neuron types before electrical signals

Students need the pathway first.

2. Emphasize ion movement early

Understanding Na⁺ and K⁺ movement simplifies everything.

3. Use diagrams repeatedly

Visual learners benefit greatly from neuron diagrams.

4. Use physical analogies

Examples like stair climbing help students remember saltatory conduction.

5. Connect biology to chemistry

Charge differences and ion gradients make the concept clearer.

Conclusion

Teaching the nervous system can initially feel overwhelming because it combines concepts from biology, chemistry, and physics. However, once students understand how ions move across membranes and how neurons are organized, the process of nerve transmission becomes far more logical.

By focusing on clear pathways, simple analogies, and the chemistry behind ion movement, teachers can help students build a deeper understanding of how the nervous system allows the body to communicate and respond to its environment.