Explain how a stimulus can result in a reflex reaction

Stimulus, e.g. pressure or heat, is detected by receptors. This impulse is carried on neurones. Neurones meet at a synapse where neurotransmitters diffuse across the synapse. The impulse is then carried along a relay neurone then the neurotransmitters cross another synapse and then are carried on a motor neurone which causes muscle contraction to exhibit the reflex action.