A neuron is a eukaryotic cell specialized to receive, integrate and transmit signals over distances. Neurons vary greatly in shape, but many share a useful functional organization.

A typical neuron contains:

• dendrites, branched processes that often receive signals from other cells;
• a cell body or soma, which contains the nucleus and much of the cell's biosynthetic machinery;
• an axon, a long process specialized for propagating electrical signals away from the soma;
• axon terminals, specialized endings that communicate with target cells.

A common information-flow pattern is

inputs on dendrites and soma
          ↓
local electrical signals
          ↓
axon initial region
          ↓
action potential along axon
          ↓
axon terminal
          ↓
signal to another cell

An action potential is a rapid regenerative electrical signal that can travel along an axon. Its detailed ion-channel mechanism is a separate concept.

The region where an axon begins, often called the axon initial segment, commonly contains many voltage-gated ion channels, channels whose gating depends on membrane voltage, and is an important site for initiating action potentials.

Neuronal polarity is functional as well as structural

The same plasma membrane surrounds the whole neuron, but different proteins are concentrated in different regions. Dendrites, axons and terminals therefore perform different signaling roles even though they belong to one continuous cell.

This organization allows a neuron to combine many local inputs near the soma while transmitting a regenerative electrical signal over a much longer distance through the axon.

The pattern is not absolute

Not every neuron has a textbook tree of dendrites attached to one soma and one long axon. Some sensory neurons have unusual geometries, and signals can sometimes travel in directions that do not match the simplified diagram.

The reusable principle is that neurons are spatially polarized cells whose molecular specialization separates signal reception, integration, long-distance propagation and output.