Define/Explain the following terms:
$(1)$ Synapse
$(2)$ Node of Ranvier

(N/A) $(1)$ $A$ synapse is a junction between two neurons,formed by the membranes of a pre-synaptic neuron and a post-synaptic neuron,which may or may not be separated by a synaptic cleft.
$(2)$ Myelinated nerve fibres are enveloped with Schwann cells,which form a myelin sheath around the axon. The gaps between two adjacent myelin sheaths are called nodes of Ranvier.