The document compares the parasympathetic and sympathetic nervous systems. The parasympathetic nervous system is responsible for conservation of energy and its preganglionic neurons are long while postganglionic neurons are short. It uses acetylcholine as its neurotransmitter. The sympathetic nervous system is responsible for the fight or flight response and has short preganglionic neurons and long postganglionic neurons. It uses norepinephrine and acetylcholine as neurotransmitters. An upcoming video will discuss the pharmacology of the autonomic nervous system and diseases that can affect it.