Sensory neurons, motor neurons and interneurons; pyramidal cells, Purkinje cells and granule cells — how neurons are classified by job, by shape and by the genes they use.
Cells of the Nervous System
Beginner
Types of Neurons
The Editors
April 26, 2026
2 min read
In plain English
Neurons aren't all the same. Some carry information from your senses, some command your muscles, and most — the interneurons — connect neurons to each other. They also come in different shapes, and scientists now sort them by which genes are switched on too.
Beginner level: No background needed. Everyday language, everyday examples — the place to start.
Concepts to know first
Go deeper next
There are many ways to sort neurons. Each tells you something different.
By job
Sensory (afferent) neurons carry information from the body and the world toward the central nervous system — from touch receptors in the skin, light-sensitive cells in the eye, stretch sensors in the muscles. Motor (efferent) neurons carry commands out to muscles and glands. Interneurons connect neurons to each other within the brain and spinal cord. They are by far the most numerous: almost all of the brain's 86 billion neurons are interneurons in this broad sense.
By shape
Cajal classified neurons by their form. Multipolar neurons, with many dendrites and one axon, are most common. Bipolar neurons, with one dendrite and one axon, are found in the retina and the nose. Pseudounipolar neurons — most touch and pain sensory neurons — have a single stalk that splits into two branches, one going to the skin and one to the spinal cord.
Some types are famous. Pyramidal cells, with triangular cell bodies and long branching dendrites, are the main excitatory output cells of the cortex and hippocampus. Purkinje cells in the cerebellum have dendrites that fan out in a flat, extravagant tree receiving up to around 200,000 inputs. Cerebellar granule cells are tiny and so numerous they make up the majority of all neurons in the brain.
By chemistry and genes
Neurons are also classed by the transmitter they release (glutamate-releasing neurons excite their targets; GABA-releasing ones mostly inhibit) and, increasingly, by their gene expression. Single-cell sequencing projects now distinguish thousands of neuron types. The BRAIN Initiative Cell Census Network described more than 3,000 cell types in the human brain in a set of papers published in 2023.
Everyday examples & things to try
Analogy
A company's staff
Sensory neurons are the reporters gathering news from outside. Motor neurons are the delivery drivers sending orders out. Interneurons are everyone in the office in between — editors, managers, analysts — and, just like in a real company, they vastly outnumber both.
Key takeaways
- By job: sensory, motor and interneurons (the vast majority).
- By shape: multipolar, bipolar and pseudounipolar; notable types include pyramidal and Purkinje cells.
- Modern atlases classify thousands of neuron types by gene expression.
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