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In the autonomic nervous system, nerve fibers from the central nervous system to the ganglion are known as preganglionic nerve fibers.All preganglionic fibers, whether they are in the sympathetic division or in the parasympathetic division, are cholinergic (that is, these fibers use acetylcholine as their neurotransmitter) and they are myelinated.
There are two kinds of neurons involved in the transmission of any signal through the sympathetic system: pre-ganglionic and post-ganglionic. The shorter preganglionic neurons originate in the thoracolumbar division of the spinal cord specifically at T1 to L2~L3, and travel to a ganglion, often one of the paravertebral ganglia, where they synapse with a postganglionic neuron.
The white ramus communicans (pl.: rami communicantes) from Latin ramus (branch) and communicans (communicating) is the preganglionic sympathetic outflow nerve tract from the spinal cord. Each of the thoracic, and the first and second lumbar nerves contribute a white ramus communicans to the adjoining sympathetic ganglion , unlike the gray rami ...
The sympathetic ganglia here, are found in two chains: the pre-vertebral and pre-aortic chains. The activity of autonomic ganglionic neurons is modulated by "preganglionic neurons" located in the central nervous system. Preganglionic sympathetic neurons are located in the spinal cord, at the thorax and upper lumbar levels.
The parasympathetic ganglion where these preganglionic neurons synapse will be close to the organ of innervation. This differs from the sympathetic nervous system, where synapses between pre- and post-ganglionic efferent nerves in general occur at ganglia that are farther away from the target organ.
It is this ability to move superiorly and inferiorly along the chain that results in the mass response to the sympathetic nervous system. A preganglionic fibre may synapse to 15–20 postganglionic fibres. The postganglionic neurons extend across most of the body. [4]
The bodies of its preganglionic sympathetic afferent neurons are located in the lateral horn of the spinal cord. Their axons enter the SCG to synapse with postganglionic neurons whose axons then exit the rostral end of the SCG and proceed to innervate their target organs in the head. [citation needed]
Cranial nerve ganglia contain the cell bodies of cranial nerve neurons. Autonomic ganglia contain the cell bodies of autonomic nerves. In the autonomic nervous system, fibers from the central nervous system to the ganglia are known as preganglionic fibers, while those from the ganglia to the effector organ are called postganglionic fibers.