Nissl bodies are mainly composed of

$S$ - Statement: The myelin sheath around a nerve fiber contains lipids.
$R$ - Reason: This sheath prevents the impulse from leaking into adjacent nerve fibers.

Choose the correct statements about Nissl's granules from the codes given below:
$I.$ There are regular masses of ribosomes
$II.$ There are irregular masses of ribosomes and $ER$
$III.$ There are granular bodies
$IV.$ They synthesise proteins in the cell

Which of the following has non-myelinated nerve fibres?

Some cells in our body can be over a foot long. They are:

The weakest current strength that can excite a tissue is called: