ScienceTeach Video: Modelling Action Potential by Using Dominoes

Discussing 'Action Potential' is one of the most challenging topics in human physiology. When I was still learning the concept back in the University, I had a hard time figuring out the influx of ions into the axon and how this action at the cellular level can produce voltage and electrical signals. So, when we were assigned to do a learning material, we chose the topic on the generation of action potential.

Here's the script I made for the above video clip. Enjoy learning.

The body’s information system is built from billions of interconnected cells called neurons. A nerve cell or a neuron consists of many different parts. The cell body or soma is the life support center of the neuron. The dendrites are branching extensions at the cell body. They receive messages from other neurons. The axon is a single extension of a neuron which is covered with myelin sheath to insulate and speed up messages through neurons. The terminal branches of axon are endings that transmit messages to other neurons. Action potential is a neural impulse. It is a brief electrical charge that travels down an axon and is generated by the movement of positively charged atoms in and out of channels in the axon’s membrane.

The propagation of a nerve impulse down an axon can be modelled by a row of falling dominoes.

• Resting potential is the state when no impulse travels along the neuron.

• All or none response. This is illustrated by the fact that the push on the first domino has to be strong enough to knock it down; pushing harder however, does not affect the impulses’ speed.

• This shows how the action potential affects one area of the axon at a time and is sequentially passed on from one section to the next.

• Dominoes lying on the table illustrate the neuron’s refractory period: the axon is not immediately able to convey a new action potential .

• The dominoes can also be used to demonstrate that more than one action potential can be traveling along the axon at the same time.

• Forming a domino line that branches out illustrates axon collaterals in which the action potential affects all the branches equally.

• The dominoes can also be used to demonstrate how myelineation increases the speed of transmission. 

• The action potential travels faster it if can jump from node to node rather than having to pass on sequentially. This is called saltatory conduction and the nodes are called the nodes of Ranvier.

When one of the channels in the axon’s membrane becomes dysfunctional, it could have serious effects as in the case of Multiple Sclerosis disease in which myelin sheaths around axons of the brain and spinal cord are damaged.