Synapse

A junction between 2 neurons across which a signal can pass. At a synapse, the 2 neurons do not come directly into contact but are separated by a gap called the synaptic cleft. When an electrical signal passing along a neuron reaches a synapse, it causes the release of a chemical called a neurotransmitter. The neurotransmitter travels across the synaptic cleft to the surface membrane of the next neuron, where it changes the electrical potential of the membrane. Signals can be transmitted across a synapse in one direction only. Most drugs affecting the nervous system work as a result of their effects on synapses. Such drugs may affect the release of neurotransmitters, or they may modify their effects.