A specific type of synapse 'X' allows the direct flow of electrical current from one neuron to another, resulting in an impulse transmission that is always faster than that across other synapse types. Identify synapse 'X' and its relative abundance in the human neural system.

Step-by-step solution

At an electrical synapse, the membranes of pre- and post-synaptic neurons are in very close proximity, allowing electrical current to flow directly from one neuron into the other. This direct flow makes impulse transmission across an electrical synapse always faster than that across a chemical synapse. However, according to NCERT, electrical synapses are rare in the human neural system. Therefore, synapse 'X' is an electrical synapse and it is rare. Answer: Electrical synapse; Rare