Comparison of Sympathetic and Parasympathetic Nervous Systems

Sympathetic and parasympathetic nervous systems are two divisions of the autonomic nervous system of body. They are closely coordinated with one another to regulate the functions of human body. In the lines below a brief comparison of the two systems is provided.

Sympathetic Nervous System

1. All neurons forming this system originate from T1 to L2 segment of spinal cord. So it is called thoracolumbar outflow.
2. Pre-ganglionic fibers are short, relay either in lateral ganglia or collateral ganglia
3. Post-ganglionic fibers are long Nerve endings are adrenergic in nature except in sweat gland
4. Functionally, sympathetic nerves are vasomotor, sudomotor and pilomotor to skin. It is seen when subject is in fear, fight and flight position. It dilates skeletal muscle blood vessels
5. Effect is widely diffused and directed towards mobilization of resources and expenditure of energy during emergency and emotional crisis
6. It supplies visceral blood vessels, skin. Afferents from viscera and specific area of skin reach the same spinal segment to go to the cerebrum. Since pain is better appreciated from the skin, it appears to be coming from skin rather than the viscera. This is the basis of referred pain.

Parasympathetic Nervous System

1. All neurons forming this system originate from brain (Ill, VII, IX, X cranial nerves) and S2—S4 segment of spinal cord. So it is called craniosacral outflow.
2. Pre-ganglionic fibers are very long reaching up to terminal ganglia mostly on viscera. Postganglionic fibers are short
3. Nerve endings are cholinergic in nature
4. Functionally, it is seen when subject is fully relaxed. Parasympathetic system has no effect on skin
5. Effect is discrete, isolated, directed towards conservation and restoration of the resources of
6. It only supplies viscera

For complete details visit the following links:

• Sympathetic nervous system
• Parasympathetic nervous system