9 Differences between Sympathetic Nervous system and Parasympathetic Nervous System

In man, the nervous system consists of central nervous system (CNS), autonomic nervous system (PNS) and autonomic nervous system (ANS).  Central nerves system (CNS) includes brain and spinal cord, peripheral nervous system (PNS) includes cranial nerves and spinal nerves. The autonomic nervous system (ANS) includes nerve chains on either side of the vertebral column. It includes sympathetic and parasympathetic divisions.

The ANS regulates the internal environment of the animal’s body by controlling smooth and cardiac muscles and other involuntary actions. ANS consisting of motor nerves and ganglia. ANS is also called visceral efferent nervous system, is made up of two opposing divisions -sympathetic and parasympathetic.

Sympathetic nervous system (Thoracico-lumbar outflow) is represented by 21 sympathetic ganglia on either side of spinal cord. It receives preganglionic sympathetic fibres from the spinal cord which make their exit along with thoracic and lumbar nerves.

Parasympathetic nervous system (Cranio sacral outflow) consists of preganglionic para sympatheic fibres, parasympathetic ganglia and postganglionic parasysympathetic fibres. 

Sympathetic Nervous system vs Parasympathetic Nervous System

Sympathetic Nervous system	Parasympathetic Nervous System
Preganglionic nerve fibre is small sized	Preganglionic nerve fibre is larger
Dilates pupil	Constricts pupil
Increases lacrimal glands secretion	Inhibits lacrimal glands secretion
Inhibits salivary and digestive glands	Stimulates salivary and digestive glands
Accelerates heart beat	Retards heart beat
Inhibits gut peristalsis	Stimulates gut peristalsis
Contracts anal sphincter	Relaxes anal sphincter
Relaxes urinary bladder	Contrasts urinary bladder
Vasoconstriction in general and vasodilation  (brain, heart, lungs and skeletal muscles	Vasodilation of coronary vessel