Solution –  travelling of the electrical impulses takes place in the neurons . When it is transmitted to another neuron it takes the form of the neurotransmitter .

Neurotransmitter are specialized chemicals . They enter the neuron only by a specialized channels . In dendrites such channels are present but absent in the axons .Neurotransmitters are able to enter the dendrites . Because of all this the flow of signals in a synapse from axonal end of one neuron to dendritic end of another neuron and not in the reverse .