Physiology of Sympathetic nervous system
Cell bodies of preganlionic sympathetic fibers are located on the intermedia lateral column of thoracic & upper lumbar spinal cord Fibers from these nucleus emerge out through respective spinal nerves from ventral root of the spinal cord. Short fibres of pre ganglionic system synapse with autonomic ganglia.
Sympathetic trunk
Sympathetic trunk is composed of chain ganglia viz vertebral ganglia. This extends from upper cervical to coccygeal vertebrae.
Sympathetic trunk is represented as a paired structure having a ganglion for each thoracic, lumbar, sacral & upper coccygeal nerve.
Segmental ganglia in the cervical region is fused into three large ganglia (cranial cervical, middle cervical & caudal vertical ganglia)
Stellate ganglion is the fusion of caudal cervical ganglia with upper two thoracic ganglia.
Fibres from trunk composed of pre ganglionic & post ganglionic system.
Sympathetic pre ganglionic fibers in thoracic cavity, neck , head, blood vessel and sweat glands synapse with vertebral ganglia.
Those supplying abdominal and pelvic organs do not synapse within the vertebral ganglia
But collateral ganglia are formed by the synapse formed by these pre ganglionic fibers with post ganglionic neurons.