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Definition

noun

A division of the (vertebrate) autonomic nervous system that is chiefly involved in producing an immediate and effective response (e.g. fight-or-flight response) during stress or emergency situations.

Supplement

The autonomic nervous system is usually categorized into two major divisions:

• sympathetic nervous system
• parasympathetic nervous system

The sympathetic system consists of the sympathetic chain of ganglia on each side of the spinal cord. The sympathetic neurons whose cell bodies are in the thoracic and lumbar regions of the spinal cord are called presynaptic (or preganglionic) neurons. These neurons communicate with the neurons of the peripheral nervous system, called postsynaptic (or postganglionic) neurons by way of chemical synapses.

Most synaptic neurons use noradrenaline as a post-ganglionic neurotransmitter.

Compare: parasympathetic nervous system

See also: autonomic nervous system