A synapse is the gap between two neurons. For an electrical impulse to travel from one neuron to the next, it must pass across a synapse.So, when an electrical impulse reaches the end of a neuron, it causes the release of neurotransmitters, which are a type of chemical messenger. The neurotransmitters diffuse across the synapse and bind to receptors on the membrane of the next neuron, triggering this neuron to transmit an electrical impulse.