The terminal buttons, also called synaptic bulbs, synaptic buttons or terminal axons, is the end portion of the axon that divides to produce a series of terminals that form synapses with other neurons or with muscle or gland cells. In the bulbs neurotransmitters are stored in packets as bubbles, called vesicles. When a nervous impulse arrives at the synapse, some vesicles go to the end of the bulb and pour out its neurotransmitter. It crosses the crack or synaptic space to the target cell and activates special receptors. If the target cell is a neuron, the receptors activate it to "fire." Then the enzymes break down the neurotransmitter.
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