BRAINCAKESynapses
A synapse is the junction between two neurones, or between a neurone and an effector cell such as a muscle fibre (a neuromuscular junction). An action potential cannot cross the gap, so the signal is carried across by a chemical, a neurotransmitter.
A synapse has three parts:
• the presynaptic neurone ends in a swelling called the synaptic knob, which contains many mitochondria and synaptic vesicles full of neurotransmitter
• the synaptic cleft, a gap about 20 nm wide between the two cells
• the postsynaptic membrane, which has receptor proteins that bind the neurotransmitter
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All 38 lessons in Mammalian Nervous System · All Edexcel A-level Biology topics