Notes

• Preganglionic fibers (thoracic and superior lumbar) synapse in ganglia near spinal cord.
• Preganglionic fibers are short (they go from CNS to ganglia).
• Postganglionic fibers are long. (contained in the sympathetic ganglia).

Fight or Flight Sympathetic division readies body for crisis. Increase in sympathetic activity:

• Stimulates tissue metabolism
• Increases alertness

Structure of the Sympathetic Division

• Preganglionic neurons located between segments T1 and L2 of spinal cord.
• Ganglionic neurons in ganglia near vertebral column.
• Cell bodies of preganglionic neurons in lateral gray horns.
• Axons enter ventral roots of segments.

SANS Ganglionic Neurons Occur in three locations:

• Sympathetic Chain Ganglia
• Collateral Ganglia (innervate organs)
• Adrenal Medullae

Organization of Sympathetic Division Ventral roots of spinal segments T1 - L2 contain sympathetic preganglionic fibers.

Sympathetic Innervation The Sympathetic innervation is generally widespread, while the Parasympathetic one is generally much more local.

Adrenal Medulla

• Preganglionic fibers entering adrenal gland proceed to center (adrenal medulla).
• Modified sympathetic ganglion.
• Preganglionic fibers synapse on neuroendocrine cells.
• Specialized neurons secrete hormones into bloodstream.

Generalized Sympathetic Activation

• Release of Epinephrine (Adrenaline) by Adrenal Medulla.
• Affect alpha and beta receptors throughout body (these work through G Proteins).