Sympathetic nervous system: Ganglia
Basic, Organ-Based and Clinical Sciences
The sympathetic nervous system’s pre-ganglionic fibers originate within the thoracolumbar region of the spinal cord. From the spinal cord, the nerve fibers extend primarily to paired ganglia within sympathetic chains, located lateral to the vertebral column, within the paravertebral space. The ganglia are linked together via myelinated axons, which form the sympathetic trunk. The chain extends from the upper neck to the coccyx. The pre-ganglionic fibers course up and down the paired ganglia, leading to a diffuse response to a given stimulus. 1
Acetylcholine is the main neurotransmitter of the sympathetic ganglion, adrenal medulla, and sweat glands.2 After a given stimulus, acetylcholine is released from the end of the pre-ganglionic sympathetic neuron, leading to the eventual release of norepinephrine.
The sympathetic neurotransmitters are synthesized from tyrosine at post-ganglionic nerve endings to eventually create dopamine, which is hydroxylated to form norepinephrine. The neurotransmitter is then stored within a vesicle awaiting postganglionic nerve stimulation. After stimulation, the vesicle merges with the cell membrane to release its contents into the synapse. Norepinephrine, once released, binds with its target adrenergic receptor, activating a G-protein messenger cascade.3