Axon Terminal

What is an axon terminal?

An axon terminal, also called a synaptic terminal or bouton, is a specialized region of an axon that communicates with a target cell. At a chemical synapse, the terminal contains vesicles holding neurotransmitter. The receiving cell can be another neuron or a muscle cell.

Axon terminal function: chemical transmission

The Neuroscience textbook explains that arrival of an action potential opens voltage-sensitive calcium channels. Calcium entry promotes vesicle fusion and transmitter release. The transmitter crosses the synaptic cleft and acts on receptors in the receiving cell.

The receiving cell’s response depends on the transmitter, receptor, and cellular conditions. A chemical signal can increase or decrease the receiving neuron’s activity.

Example: the neuromuscular junction

At the neuromuscular junction, a motor nerve terminal releases acetylcholine. It binds to receptors on the muscle fiber and activates the muscle membrane, helping initiate contraction.

Axon terminals and plasticity

Changes on the transmitting side of a synapse can contribute to plasticity: changes in how strongly cells communicate. The release mechanism is one part of that process, not a complete explanation of how a memory forms.

This description concerns chemical synapses. Electrical synapses work differently: current passes directly between coupled cells.