What is the difference between ANS, CNS, and SNS?
Here's the best I've got.
The Central Nervous System (CNS) is made up of the brain and the spinal column.
The Autonomic Nervous System (ANS) is the system that connects the brain and internal organs. This works largely by itself keeping your temperature at a reasonable level, heart pumping, etc.
The Sympathetic Nervous System (SNS) This is what prepares the body for the fight or flight mode. It stimulates the postganglionic neurons for acetylcholine (ACh) Postganglionic neurons release norepinephrine.
Apologies for it being quite short, yet I hope it helps a bit.