Definition
A neuron is the basic signaling cell of the nervous system — the unit out of which every thought, feeling, and behavior is ultimately built. The human brain contains tens of billions of them, each capable of receiving signals, deciding whether to fire, and passing a signal along.
A neuron has a recognizable shape: a branching tree of dendrites that receive incoming signals, a cell body that integrates them, and a long axon that carries the outgoing signal away to other cells. Behave uses the neuron as the smallest building block in its causal account of behavior.
Why it matters
How it works
A neuron is constantly summing. Its dendrites collect signals from thousands of other neurons — some excitatory, nudging it toward firing, some inhibitory, holding it back. The cell body adds them up. If the net excitation crosses a threshold, the neuron fires an action potential down its axon.
At the axon's end, the electrical signal is converted back into a chemical one, releasing neurotransmitter onto the next cell across a synapse. A neuron is therefore a tiny decision-maker: it takes a flood of votes and produces a single all-or-nothing output. Behavior emerges when billions of these decisions are coordinated.