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This lesson covers how nerve impulses cross the gap between neurones (synapses) and how reflex arcs produce fast, automatic responses. This is essential content for Edexcel GCSE Biology (1BI0) Topic 2: Cells and Control.
A synapse is the tiny gap (also called the synaptic cleft) between two neurones, or between a neurone and an effector (such as a muscle). Neurones do not physically touch each other — there is always a synapse between them.
Electrical impulses cannot jump across the synaptic gap. Instead, the signal is transmitted by chemical messengers called neurotransmitters. The process works as follows:
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