AUTONOMIC NERVOUS SYSTEM

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AUTONOMIC NERVOUS SYSTEM

• BY
• DR.A.A.OREMOSU
• DEARTMENT OF ANATOMY
• CMUL

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Overview of ANS

• Pathway for Visceral Motor Output
• ANS has two antagonistic divisions
• Sympathetic
• Parasympathetic
• ANS output always involves two neurons between
  spinal cord (CNS) and effector.

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• Nerve supply of visceral structures
• Sympathetic- fright or flight response
• Parasympathetic- recovery from flight/fright
  response
• CNS-gnaglion- effector organ
• Sympathetic also supplies blood vessels of skin,
  arector pili muscles, arterioles sweat glands

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CNS- Ganglion- effector organ
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Ganglia

• Lie outside CNS
• Sympathetic-ganglia are in (a) sympathetic chain
  (b) ganglia around large arteries
• Parasympathetic- ganglia present ON or IN organ
  which they supply
• Preganlionic fibres- white rami
• Postganglionic fibres- gray rami

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Parasympathetic outflow-craniosacralSympathetic
outflow-thoracolumbar
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Thoraco lumbar out flow

• T1- L2(3)
• Supplies almost all viscera
• Sympathetic chain 3 cervical, 10-12 thoracic, 4
  lummbar, 4-5 sacral, I coccygeal ganglia
• The 2 chain unite _at_ ganglion impar in front of
  coccyx

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Schematic representation of the ANS
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• Synapsing takes place in ganglia
• Naming of neurons

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Fig 17.3
neuron 1 preganglionic presynaptic neuron 2 Ganglionic postsynaptic effector
Preganglionic fiber (axon) Always myelinated Postganglionic fiber Always unmyelinated
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Sympathetic Division

• Thoracolumbar division
• Preganglionic neurons (cell bodies) located
  between T1 L2 of spinal cord
• Ganglionic neurons (cell bodies) in ganglia near
  vertebral column
• Paravertebral ganglia sympathetic chain ganglia
• Prevertebral ganglia collateral ganglia
• Special case adrenal medulla
• Effects of Sympathetic Division?

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The splanchnic nerves

• Greater splanchnic(GS) T5-9
• Lesser splanchnic (LS) T10-11
• Least splanchnic (LeS) T12
• Fibres pass through sympathetic chain without
  relaying
• End in ganglia
• GS-coeliac
• LS-superior mesenteric
• LeS-may be absent-superior mesenteric

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Special Case Adrenal medulla
Fig. 17-6

• Modified sympathetic ganglion
• Terminus for neuron 1, stimulates specialized
  2nd order neurons with very short axons in
  adrenal medulla to release NT into blood stream
  ( hormones)
• Epinephrine (adrenalin) 80 and norepinephrine
  (noradrenalin)
• Endocrine effects are longer lasting than
  nervous system effects

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Sympathetic Neuroeffector Junctions
Differ from somatic neuromuscular
junctions Varicosities
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Summary of Sympathetic Division

• A. Neuron 1 is short, neuron 2 is long
• B. Synapsing occurs in prevertebral chain ganglia
  or paravertebral collateral ganglia
• C. Neuron 1 releases Ach, usually neuron 2
  releases NE
• D. Prepares for emergency action, excitatory to
  many organs, inhibitory to others ( digestive for
  example)
• E. Effects very widespread and somewhat persistent

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Para SympatheticDivision

• Craniosacral division
• Preganglionic neurons (cell bodies) located in
  brain stem sacral segments of spinal cord
• Ganglionic neurons (cell bodies) in ganglia near
  target organs Intramural ganglia
• Effects of parasympathetic division ?

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Craniosacral outflow

• Cranial nerves 3,7,9,10
• Nucleus, nerve, ganglion organ supplied
• Nuclei are Edinger westphal, superior salivatory,
  inferior salivatory, dorsal motor nucleus of
  vagus respectively
• Ganglia ciliary-CN-III
• Sphenopalatine-CN VII
• Submandibular- CN VII
• Otic -CN IX
• Numerous(thorax,abd.)- CN X

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PARASYMPATHETIC INNERVATION
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• III-Supply intrinsic eye muscles
• VII-Glands of nose, mouth pharynx
• VII IX-Salivary glands
• V-Organ- heart, respiratory system, abdominal
  viscera

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Sacral part

• Nervi eregentes- wandering nerves
• Supplies pelvic viscera
• Produces erection in males
• Relaxes internal urethral sphincter
• Root value S2,3,4
• Stimulation empties bladder

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INNERVATION OF THE BLADDER
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Summary of Parasympathetic Division

• A. Neurons 1 are long, come from the brain stem
  or sacral spinal cord, run with the spinal or
  pelvic nerves and produce ACh.
• B. Neurons 2 are short, produce ACh, and may be
  either excitory or inhibitory.

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Anatomy of Dual Innervation

• Each organ receives innervations from
  sympathetic and parasympathetic fibers
• Fibers of both divisions meet commingle at
  plexuses to innervate organs close to those
  centers
• Names of plexuses derived from locations or
  organs involved

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