The human neural system comprises

The autonomic neural system in humans is composed of which of the following?

$P$ nerve fibers transmit impulses from tissues/organs to the $CNS$ and $Q$ nerve fibers transmit regulatory impulses from the $CNS$ to the concerned peripheral tissues/organs.
$\quad\quad\quad P\quad\quad\quad Q$

In humans,the visceral organs are innervated by:

$P$ - Contains unmyelinated nerve fibers.
$Q$ - Contains myelinated nerve fibers.
$I$ - Spinal nerves
$II$ - Autonomic neural system
$III$ - Somatic nerve fibers
$IV$ - Cranial nerves
Select the correct option for $P$ and $Q$.
$\quad\quad P$ $\quad$ $\quad$ $Q$

What are the histiocytes of the brain?