Nissl's granules are absent in

In a neuron,ion channels are made of $.....P....$ and are located in $.....Q.....$.
$\quad\quad P\quad\quad Q$

Neurons receive signals through their . . . . . . and send signals to other neurons through their . . . . . . .

Four healthy people in their twenties were involved in injuries resulting in damage and death of a few cells of the following types. Which of these cells are least likely to be replaced by new cells?

Multiple sclerosis is caused by .............

The junction between two adjacent Schwann cells in a myelinated nerve fiber is known as: