How Do Neurons Communicate? Electrical, Chemical Signals

Neurons communicate by combining two kinds of signals: electrical and chemical. An electrical impulse called an action potential travels along the neuron’s axon. When it reaches the end of the axon, it triggers the release of chemical messengers called neurotransmitters into the synapse, the tiny gap between neurons. These chemicals bind to receptors on the next neuron, where they may set off a new electrical signal. The human brain contains roughly 86 billion neurons, each able to communicate with thousands of others, and this electrical-chemical-electrical relay, completed in milliseconds, is what lets us think, move, remember, feel, and respond to the world.

Listening before speaking

A neuron is constantly receiving information from hundreds or even thousands of other neurons, mostly through its branching dendrites. Some incoming signals make the neuron more likely to fire, while others make it less likely. The neuron continuously adds all of these messages together. You can think of it as weighing a stream of opinions before deciding whether to speak up, though a neuron’s decision is purely electrical, not a choice in any conscious sense.

The electrical stage

If the combined input reaches a critical threshold near the start of the axon, the region around the axon hillock, the neuron fires an action potential. An action potential is a brief electrical impulse created by sodium and potassium ions moving across the cell membrane. Once it starts, it travels along the axon without losing strength.

Many axons are wrapped in myelin, an insulating sheath. On these axons, the signal doesn’t spread evenly along every stretch of membrane. Instead it is regenerated at small gaps in the myelin called nodes of Ranvier, a process called saltatory conduction. It is often described as the signal jumping from node to node, which is a simplification, but the effect is real: communication becomes much faster while using less energy.

From electricity to chemistry

When the action potential reaches the axon terminal, it opens voltage-gated calcium channels. Calcium flows into the terminal and triggers small packets called synaptic vesicles to fuse with the cell membrane and release their neurotransmitters into the synaptic cleft. At this moment, the electrical signal has been turned into a chemical one.

The neurotransmitters diffuse across the gap in a fraction of a millisecond and bind to specific receptors on the receiving, or postsynaptic, neuron. Because each receptor recognizes only certain neurotransmitters, the communication stays highly precise, much like a key that fits only its own lock.

Back to electricity

Once neurotransmitters bind their receptors, ion channels on the receiving neuron open or close, changing the electrical properties of its membrane. If enough excitatory input arrives, the next neuron fires its own action potential, and the cycle repeats.

The two signaling systems complement each other. Electrical signaling is fast and carries the message within a single neuron. Chemical signaling carries the message between neurons and lets one cell influence thousands of different targets. Together they allow the nervous system to process enormous amounts of information with speed and precision.

When communication breaks down

Every sensation, movement, thought, memory, and emotion depends on this process, so disrupting any step can lead to neurological disease. In multiple sclerosis, myelin is damaged. In myasthenia gravis, transmission at the synapse is impaired. In Parkinson’s disease, dopamine signaling is deficient. In epilepsy, electrical signaling becomes abnormal. Understanding how neurons communicate helps explain both normal brain function and many neurological disorders.

This article is educational background and does not replace medical evaluation.

Related: What Is a Neuron? · Neuron Structure Explained: Parts of a Nerve Cell and Their Functions · What Is an Action Potential? · What Is a Synapse? · What Are Neurotransmitters?

References

1. Grider MH, Jessu R, Kabir R. Physiology, Action Potential. StatPearls. Updated May 8, 2023.
2. Caire MJ, Reddy V, Varacallo MA. Physiology, Synapse. StatPearls. Updated March 27, 2023.
3. Cooper GM. Signaling Molecules and Their Receptors. The Cell: A Molecular Approach. NCBI Bookshelf.