Terminal buttons are structures on the end of the axon, the trailing part of a neuron, that carry signals to neighboring neurons, glands, or muscles. When electrical signals enter a neuron, they travel down the length of the axon, which branches out to create a number of terminal buttons. Small sacs known as vesicles at each button fill with neurotransmitters and burst open when triggered by a signal from the neuron. This releases chemicals that can leap to a neighboring cell to excite or inhibit it, depending on the neurotransmitter involved.
Also known as end bulbs, terminal buttons are a key component of the anatomy of the neuron. In cases where they communicate with other neurons and gland cells, a small space known as the synapse provides room for the chemical signal to travel. At the neuromuscular junction, a neuron fires neurotransmitters across a synapse to a muscle cell, which can trigger a movement. The number of terminal buttons on any given axon can vary, and they may contain large numbers of vesicles to provide ample supplies of neurotransmitters.
![](http://images.thehealthboard.com/slideshow-mobile-small/wrist-pain-illustrated-on-man.jpg)
Neurons have different functions in the body that can lead to variations in structure. A motor neuron, for example, is involved in the regulation of movement, and thus works differently than a sensory neuron. In all cases, these specialized cells rely on the ability to communicate with extreme rapidity across a synapse. Neurons can fire so quickly that a response appears almost instantaneous, when in fact it may involve a long relay of signals from cell to cell.
![](http://images.thehealthboard.com/slideshow-mobile-small/neuron-diagram.jpg)
For example, when a sensory neuron is stimulated by the experience of pain, it can send a signal along the nerve pathways to the spinal cord, relaying a signal to the brain. The brain can signal motor neurons to tell the body to change position, thereby avoiding the sensation. Time elapsed between an experience like touching a hot pan and jerking back in pain can seem instant, illustrating how quickly the brain can respond to a situation. Large supplies of vesicles at the terminal buttons allow neurons to fire, relax, and fire again very quickly.
![](http://images.thehealthboard.com/slideshow-mobile-small/neurons-with-electrical-synapses-firing.jpg)
Research on the structure of neurons provides important information about what occurs when there are problems with the brain and nervous system. People with demyelinating diseases, for instance, experience a gradual erosion of the protective sheath which covers nerves. This degrades efficiency, making it harder for nerves to send and control signals. As a result, the patient can develop symptoms like weakness and tremors.