L1.3.3.2.1: Anatomy of ANS Divisions

• PARASYMPATHETIC DIVISION

  ● “Craniosacral division”

  ● Parasympathetic fibers — CHOLINERGIC FIBERS

  ● Preganglionic neurons originate in:

  ○ Cranial nerves III, VII, IX, and X

  ○ S2 through S4 regions of the spinal cord

  ● Synapse with terminal ganglia. From there, postganglionic axons extend to organs that are served
• SYMPATHETIC DIVISION

  ● “Thoracolumbar division”

  ● Sympathetic fibers — ADRENERGIC FIBERS

  ● Preganglionic neurons originate in:

  ○ T1 through L2
• SYMPATHETIC DIVISION

  ● Axons pass through a ramus communicans (small communicating branch) to enter a sympathetic trunk ganglion

  ● This trunk lies alongside the vertebral column on each side

  ● After synapsing at the ganglion, the axon may synapse with a second neuron at the same or different level

  ● OR, the preganglionic neuron may pass through the ganglia without synapsing and form part of the splanchnic nerves

  ○ Splanchnic nerves – travel to the collateral ganglion

  ○ Collateral ganglia – serve the abdominal and pelvic organs