An action potential is a brief reversal in electrical charge across a membrane that travels down the axon of a neuron.
Within a living organism, neurons are excited by a flow of synaptic inputs onto their dendrites and cell body from other neurons. They are also excited by receptor potentials generated by sensory organs. This activation is called an action potential which works pretty much like brain enhancing drugs. When an action potential occurs, there is a short-lived change in electrochemical charge across a neuron’s cell membrane. This change in charge activates a resting neuron, and causes excitation.
How Does An Action Potential Work?
An axon is the long, thin, cylinder-like structure of a neuron that separates into several branches, ending in terminal buttons. It is down a neurons axon that an action potential or nerve impulse is carried. This brief change in electrochemical charge is carried away from the neuron’s cell body, down the axon and into the branch-like structures it divides into. When an action potential reaches the terminal buttons located on these branches, a chemical substance called a neurotransmitter is released.
How Does a Change in Electrical Charge Occur?
The cell membrane of an axon has an electrical charge. When a neuron is at rest, the inside of the cell membrane is more negatively charged compared with the outside of the cell membrane. When an action potential occurs, the electrical charge across a cell membrane is briefly reversed. This short-lived reversal begins at the cell body and travels down the axon.
The electrical charge of a resting neuron’s axon occurs because of an imbalanced amount of positively and negatively charged ions; particles found inside and outside an axon’s cell membrane. Usually, the cell membrane is impermeable to these ions, however, tiny proteins called ion channels found within the membrane open and close, allowing some ions to flow in and out.
Ion channels found within the cell membrane are closed when a neuron is at rest, however, an action potential occurs when ion channels closest to the cell body open, and positively charged sodium ions flow into the membrane, reversing the membrane potential at that point. This reversal causes nearby ion channels to open, resulting in another reversal which continues down the length of the axon to the terminal buttons located on the end.
As said, an action potential is a brief event. As quickly as ion channels open and there is a reversal in charge, they soon close and other ion channels nearby open, releasing positively charged potassium ions from inside the axon, to the outside, returning the neuron to a state of rest.