Neuron Structure Explained: Parts of a Nerve Cell and Their Functions

Every Part of a Neuron Exists to Move a Signal One Way

Of the roughly 86 billion neurons in the human brain, no two do exactly the same job — but nearly all of them are built around the same constraint: get a signal in, decide whether it matters, and send it out in one direction, fast. That constraint is what shapes the anatomy. Every structure a neuron has — dendrites, cell body, axon hillock, axon, myelin, nodes of Ranvier, axon terminals — exists because of some part of that one-way journey, and damage to any single piece tends to disrupt a specific, recognizable part of it.

Dendrites collect, they don’t decide

Dendrites are the tree-like branches extending out from the cell body, and their job is purely to receive — connecting to other neurons through synapses and gathering incoming signals rather than generating any electrical impulse themselves. A single neuron can carry hundreds or even thousands of dendritic branches, which is what lets it listen to many other neurons simultaneously rather than just one.

The soma runs the cell and tallies the votes

The cell body, or soma, is the neuron’s metabolic center — it houses the nucleus along with mitochondria, ribosomes, the Golgi apparatus, and endoplasmic reticulum, the machinery that builds proteins, generates energy, and keeps the cell alive. But it’s doing more than housekeeping: it’s also where signals arriving from all those dendrites get integrated, the first stage of deciding whether an impulse is actually warranted.

The axon hillock is where the decision actually gets made

Where the cell body meets the axon sits the axon hillock, and this is genuinely the neuron’s decision point. Signals summed from many dendrites converge here, and if the combined activity crosses a threshold, an action potential fires. The axon hillock carries an unusually high density of voltage-gated sodium channels, which is exactly why nerve impulses almost always begin at this specific spot rather than somewhere else on the cell.

The axon is a one-way street, sometimes a very long one

Once triggered, the signal travels down the axon — a long, thin extension that, unlike the dendrites, carries information in only one direction, from the cell body toward the terminals. The length varies enormously: some axons span a fraction of a millimeter, while others — like the ones running from the spinal cord down to the foot — stretch over a meter.

Myelin is what makes speed possible

Many axons are wrapped in myelin, a lipid-rich insulating layer that dramatically speeds up conduction while reducing the energy the signal costs to send. Who builds that insulation depends on where the neuron sits: oligodendrocytes myelinate axons in the central nervous system, Schwann cells handle the peripheral nervous system. This insulation isn’t cosmetic — diseases that damage myelin, like multiple sclerosis, can significantly slow or outright block nerve conduction, which is a direct consequence of losing this specific structure.

The gaps in the insulation are the point

Myelin doesn’t cover the axon continuously — it’s interrupted by small gaps called the nodes of Ranvier, and these gaps are where the signal-boosting machinery concentrates. Loaded with voltage-gated sodium channels, the nodes let the action potential effectively jump from one node to the next rather than crawling continuously along the membrane — a process called saltatory conduction, and the reason myelinated axons conduct so much faster than unmyelinated ones.

Where the signal becomes chemistry

At the far end of the axon, the signal reaches a cluster of small branches called axon terminals. When the action potential arrives here, it triggers neurotransmitter release into the synapse — the point where an electrical signal becomes a chemical one, passed on to the next neuron, a muscle cell, or a gland.

What goes wrong tells you where the damage is

Because each of these structures does something distinct, damage tends to produce recognizably different disorders depending on which part is affected:

Structure	Associated disorders
Dendrites	Alzheimer’s disease (loss of dendritic spines)
Axon	Traumatic axonal injury, peripheral neuropathy
Myelin sheath	Multiple sclerosis, Guillain-Barré syndrome
Axon terminals	Botulism, Lambert-Eaton myasthenic syndrome

That mapping isn’t incidental — it’s a direct consequence of the division of labor built into the cell’s structure, which is why understanding neuron anatomy explains so much about why particular neurological diseases produce the specific symptoms they do.

Related: What Is a Neuron? · What Is a Synapse? · What Is an Action Potential? · What Are Neurotransmitters? · How Do Neurons Communicate?

References

• National Institutes of Health. Information about the Brain. NIH Curriculum Supplement Series. NCBI Bookshelf.
• Standring S, ed. Gray’s Anatomy: The Anatomical Basis of Clinical Practice. 42nd ed. Elsevier; 2020.
• Caire MJ, Reddy V, Varacallo MA. Physiology, Synapse. StatPearls. Updated March 27, 2023.