Release of gastro-intestinal secretion and movement after ingestion of food is brought about by

The system that transmits impulses from the $CNS$ to the involuntary organs and smooth muscles of the body is:

$P$ - 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 $Q$.
$\quad\quad P$ $\quad$ $\quad$ $Q$

Which are the two parts of the $PNS$?

Differentiate between the invertebrate neural system and the vertebrate neural system.

Which system transmits impulses from the $C.N.S.$?