(d) : Synapse is the close proximity of the axon of one neuron and the dendrite or cyton of another neuron with a gap of just about 200 Å in between. A nerve impulse is transmitted across the synapse by the release from the presynaptic membrane of neurotransmitter, which diffuses across the synaptic cleft to the post synaptic membrane. This triggers the propagation of the impulse from the dendrite along the length of the post synaptic neuron.