Unidirectional flow of a nerve impulse is at:

A i.e. SynapseSynapses generally permit conduction of impulses in one direction only, from presynaptic to post-synaptic neurons. Any impulse conducted antidromically up the axons dies out because, post synaptical pa of neurons lack chemical synaptic vesiclesQ that are needed for synaptic transmission. Therefore an impulse arriving at the post synaptic membrane cannot release synaptic mediator.Axons can conduct impulse in both direction.Dendrites are found on the axon's endings and so behave in the same way as the axons i.e. bi-directional.