Neuron Structure

Neurons are the cells of the nervous system that transmit electrical signals. They come in a variety of shapes and sizes but generally have some common features. All neurons have a cell body, also called the soma, that contains the nucleus. Most neurons also have dendrites and an axon that extends from the cell body.

Dendrites are often highly branching and they receive signals from other neurons at junctions called synapses. The axon, on the other hand, transmits signals to neurons and other cells. The axon hillock, where the cell body meets the axon, generates the action potential, the primary form of electrical signaling in the nervous system.

Axons are often wrapped in a fatty myelin sheath, made by support cells called glia, which insulates them, helping to maintain the electrical signal as it is transmitted along. The nodes of ranvier, gaps in the myelin sheath, are regions where the action potential is repeatedly regenerated down the axon.

At the end of the axon is the terminal, containing synaptic vesicles filled with neurotransmitter molecules. When an action potential reaches the terminal, neurotransmitter is released into the synaptic cleft, a region of space between cells at a synapse. Depending on the type of channel, the neurotransmitter can help transmit the signal to the next cell.