How is a nerve impulse transmitted across a synapse?

Synapses are a gap or a junction between two neurones. When a nerve impulse is travelling along the axon of the first neurone and the impulse reaches the axon terminal (the end of the axon), a chemical called neurotransmitter is released from the axons terminal that diffuses across the synapse and binds to the receptors found on the second neurone's head.