How is a nerve impulse transmitted across a synapse?

A synapse is gap between two neurones. When a nerve impulses travels along the axon reaches the end of the pre-synaptic neurone, the release of chemical messengers (called neurotransmitters) is triggered. These molecules diffuse across the synapse and bind to receptors on the postsynaptic neurone. Here, they cause a response and cause the nerve impulse to be transmitted along the second axon.