What Is a Neuron? How Nerve Cells Work

A neuron is a nerve cell that receives, processes, and passes on information. Neurons send electrical signals and chemical messengers between different parts of the body, and they are the basic building blocks of the brain and nervous system. They are what allow you to think, move, feel, learn, and remember. The human brain contains roughly 86 billion of them, working together as an extraordinarily complex communication network.

A cell built for communication

The neuron is the basic functional unit of the nervous system. Most cells in the body are specialized for jobs like storing energy, building tissue, or fighting infection. Neurons are specialized for communication. They receive information from other neurons, process it, and send signals on to other nerve cells, muscles, or glands. That constant exchange lets the nervous system control nearly every function of the body.

Four main parts

A typical neuron has four main parts, and it helps to picture a tree. Dendrites are like branches: they receive signals from other neurons and carry that information toward the cell body. The cell body, or soma, is like the trunk. It contains the nucleus and the machinery that keeps the neuron alive, and it also processes incoming information before a signal is sent on. The axon is like a long root reaching away from the trunk. It carries electrical signals away from the cell body, and its length varies enormously, from a few millimeters to more than a meter. At the end of the axon are the axon terminals, where neurotransmitters are released to communicate with the next cell when an electrical signal arrives. The tree image is only about shape; unlike a tree, a neuron’s signals travel in one main direction, from branches toward roots.

Electrical and chemical signaling

Neurons communicate in two stages. First, an electrical signal called an action potential travels along the axon. When it reaches the end of the neuron, chemical messengers called neurotransmitters are released into the synapse, the junction between cells, and carry the signal across to the next neuron. This combination of electrical and chemical signaling happens continuously throughout the nervous system.

Three kinds of neurons

Neurons play different roles depending on where they are. Sensory neurons carry information from the body to the brain and spinal cord. Motor neurons send commands from the brain and spinal cord to muscles and glands. Interneurons connect other neurons within the brain and spinal cord, and most neurons in the human brain are interneurons.

Not the only cells in the brain

Every thought, memory, movement, emotion, and sensation depends on neurons, and without them the brain could not process information or communicate with the body. But neurons are not the only cells in the brain, a common misunderstanding. The brain also contains glial cells, which support, protect, and nourish neurons. Neurons are the main communication cells, working within a larger cellular team.

Related: What Is the Brain? · How Does the Brain Work? · What Is the Central Nervous System · What Is a Synapse? · What Is an Action Potential?

References

1. National Institutes of Health. Information about the Brain. NIH Curriculum Supplement Series. NCBI Bookshelf.
2. Caire MJ, Reddy V, Varacallo MA. Physiology, Synapse. StatPearls. Updated March 27, 2023.
3. Grider MH, Jessu R, Kabir R. Physiology, Action Potential. StatPearls. Updated May 8, 2023.