Non-excitable cells,found among the neurons are called

The Nissl's granules are present in:

Neurons with long axons are called

The myelin sheath is continuous. If the myelin sheath were continuous in a myelinated nerve fiber,what would happen to nerve conduction?

Analogy type question:
$(1)$ Myelinated nerve fiber is covered by Schwann cells : The gap between two adjacent myelin sheaths : .......
$(2)$ Multipolar neuron : One axon and two or more dendrites :: Bipolar neuron : ..........

Synaptic knob is a bulb-like structure which is present: