Explanation:This question was inspired by Mats Carlberg of Sweden.The exploration of electrophysiology culminates in exploring how the brain processes information.The combined depolarisations of both would exceed threshold.Neuron 2 blocks signals travelling down neuron 1.Neuron 2 does not innervate neuron 4.Testing the idea of frequency as well as networking. Two fires from 3 would lift 4 above the threshold.