Autonomic nervous system (ANS) is a part of the peripheral nervous system and it is divided into two types,
(a) Sympathetic nervous system
(b) Parasympathetic nervous system
The sympathetic nervous system is also called as the thoraco-lumbar division, as it contains the preganglionic neurons of the thoraco-lumbar outflow. The sympathetic nervous system is concerned with preparing the organism for emergency (fight or flight).
The parasympathetic nervous system is also called as the cranio-sacral division, as it contains the preganglionic neurons of the cranio-sacral outflow. It is mostly concerned with vegetative functions, such as motility and secretions of gastrointestinal tract. This system is essential for normal existence.
Most of the physiological responses of sympathetic and parasympathetic divisions are antagonistic of each other.
Thus, the blanks can be filled with sympathetic; parasympathetic; in opposition.