When an electrical signal, called an action potential, travels through a neuron, it triggers the release of neurotransmitters from that cell. These neurotransmitters travel across a small distance to the next (upstream) neuron, where they bind to specific proteins on the membrane surface. Neurotransmitters can do a wide range of things, like silence the upstream neuron, or make it more electrically active. It can trigger release of internal chemicals in the cell, which may turn genes on and off. Some neurotransmitters, like dopamine or serotonin, are specific to a tract of neurons, and can be responsible for overall behaviors like mood or control of motion.