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The basic signaling cell of the nervous system, transmitting electrical and chemical messages via dendrites, a soma, and an axon.
Medically reviewed & updated
The neuron, or nerve cell, is the fundamental working unit of the nervous system. Neurons receive, process, and transmit information using electrical impulses and chemical signals, forming the circuits that underlie everything from reflexes to thought.
A typical (multipolar) neuron has three main parts. The soma (cell body) contains the nucleus and the organelles that keep the cell alive and manufacture proteins. Dendrites are branching projections that extend from the soma and serve a receptive role, collecting incoming signals from other neurons and relaying them toward the cell body, where they are integrated. The axon is a single, often long fiber that carries the resulting electrical impulse away from the soma toward its targets. Axon length varies enormously—from a fraction of a millimeter to about a meter for cortical projection neurons. Many axons are wrapped in a fatty myelin sheath that speeds conduction. The axon ends in terminals that form synapses with the dendrites, soma, or axon of other neurons, or with non-neuronal targets such as muscle fibers.
When a neuron is sufficiently stimulated, it fires an action potential—a brief electrical wave that travels down the axon. At the synapse, this signal is converted into a chemical message: the axon terminal releases neurotransmitters that cross the tiny synaptic gap and bind receptors on the next cell, exciting or inhibiting it. Neurons are supported by glial cells (such as oligodendrocytes and Schwann cells, which form myelin), which protect, nourish, and insulate them.
Because neurons drive all nervous-system activity, their damage underlies many disorders. Demyelinating diseases such as multiple sclerosis strip the myelin sheath and slow conduction. Neurodegenerative conditions such as Alzheimer's, Parkinson's, and ALS involve progressive neuron loss. Mature central-nervous-system neurons have limited ability to regenerate, which is a key reason brain and spinal cord injuries often cause lasting deficits.
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