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Another major difference between the two ANS (autonomic nervous systems) is divergence. Whereas in the parasympathetic division there is a divergence factor of roughly 1:4, in the sympathetic division there can be a divergence of up to 1:20. This is due to the number of synapses formed by the preganglionic fibers with ganglionic neurons.
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.
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 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 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.
The preganglionic neuron can pass through the paravertebral ganglion without synapsing, and therefore continue as a preganglionic nerve fiber (Splanchnic nerves) until it reaches a distant collateral ganglion anterior to the vertebral column (Prevertebral ganglia). Once inside the prevertebral ganglia, the individual neurons comprising the ...
The second-order neurons ascend to the brain stem and thalamus in the ventrolateral, or anterolateral, quadrant of the contralateral half of the spinal cord, forming the spinothalamic tract. [1] The spinothalamic tract is the main pathway associated with pain and temperature perception, which immediately crosses the spinal cord laterally. [ 1 ]
The lateral grey column is composed of sympathetic preganglionic visceral motor neurons which are part of the autonomic nervous system. [1] An in-depth study of the lateral grey columns in the thoracic region of rats revealed two types of cells.