Ex-plain... Action Potential

Ever wondered how an action potential in your brain actually works? Well, considering that it is the FIFA World Cup right now, I’ll explain it in football terms.

For our analogy, we assume the neuron itself to be the Metlife stadium (or as FIFA like to call it, the New York New Jersey Stadium), where the 2026 World Cup Final will take place. Fans, in this depiction, are individual ions that create electrical signals in our stadium (or neuron). It is currently 10:00 on matchday. The stadium is at rest. All the fan gates are closed apart from the VIP entrance. Only highly esteemed VIPs are allowed access into the stadium. 

These VIPs are our potassium ions. 

Now, these VIPs like a breath of fresh air once in a while, and they hate overcrowded spaces. Thus, the VIPs often go in and out of the stadium to maintain a balance. By 12pm, there are just as many VIPs outside the stadium as there are inside the stadium lounge. 

Now, as the match approaches, the fan gates are readied. Outside the stadium, a massive, rowdy crowd of general admission fans (sodium ions) are packed tightly against the barricades. 

There are different types of gates all around the stadium. The first type is our “gated channels”. There are two types of gated channels: voltage-gated and ligand-gated. 

For voltage-gated channels, we like to think of them as electronic turnstiles. There are electronic sensors in the stadium walls that, once registering a sudden crowd pressure, automatically trigger every single electronic turnstile (voltage-gated sodium channels) down the entire corridor to snap open at once. The massive flood of sodium fans outside stampedes into the stadium. The energy inside instantly flips from negative to incredibly positive and chaotic (depolarisation). This is essentially what we mean by an action potential.

On the other hand, ligand-gated gates require a ticket to be shown to a steward. These tickets are highly specific and only fans who present the specific ticket to the stewards would be allowed in. In neuroscience, these ‘tickets’ are specific neurotransmitters that bind to receptors (stewards) attached onto the channel (gate). 

The stadium is now dangerously overcrowded, much like a repeat of Wembley Stadium during the 2020 Euro Finals. As a result, security slams the entry turnstiles shut so no more fans (sodium ions) can enter. To relieve the pressure, they open up the back doors (voltage-gated potassium channels) for the VIPs (potassium ions) to escape the chaos. This brings the energy inside the stadium back to a manageable level (known as repolarisation). 

The stadium is finally quiet now, but there is a huge problem. All the fans are in the wrong places. The rowdy sodium fans are inside the seats, and the VIP potassium guests are stranded outside in the parking lot. To deal with this, the stadium clean-up crew (The Sodium-Potassium Pump) has to chug a lot of energy drinks (ATP) and manually escort the sodium fans out onto the street while rounding up the potassium VIPs and inviting them back. 

Sounds terribly plutocratic doesn’t it!