How does an unmyelinated axon differ from a myelinated axon?

Identify $P, Q,$ and $R$ in the given neuron.

Where are the "Nodes of Ranvier" found?

Select the correct option for dendrites and axons.
$I -$ Short fibers,$II -$ Long fibers,$III -$ Transmit impulses away from the cell body,$IV -$ Transmit impulses towards the cell body,$V -$ Highly branched fibers,$VI -$ Unbranched fibers
Dendrites $\quad$ $\quad$ Axon

In a myelinated axon, what is the gap between two adjacent myelin sheaths called?

Which of the following has non-myelinated nerve fibres?