True about nerve impulse is:

C i.e. Travels in one direction at synapse Axons can conduct nerve impulses in either directionQ unlike synapses, which permit conduction of nerve impulses in one direction only. Conduction of nerve impulses, although rapid, is much slower than that of electricity.Q Summation - A single subthreshold stimulus fails to produce an AP. But if a second stimulus, which also, is subthreshold, is applied sufficiently quickly after the 1st one, the two stimuli are summated & excitation results.