AUTONOMIC NERVOUS SYSTEM BYDR.A.A.OREMOSU DEARTMENT OF ANATOMY CMUL

Overview of ANS Pathway for Visceral Motor Output ANS has two antagonistic divisions: 1.Sympathetic 2.Parasympathetic ANS output always involves two neurons between spinal cord (CNS) and effector.

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

CNS- Ganglion- effector organ

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

Parasympathetic outflow-craniosacral Sympathetic outflow-thoracolumbar

Thoraco lumbar out flow T1- L2(3) Supplies almost all viscera Sympathetic chain 3 cervical, thoracic, 4 lummbar, 4-5 sacral, I coccygeal ganglia The 2 chain ganglion impar in front of coccyx

Schematic representation of the ANS

Synapsing takes place in ganglia Naming of neurons: neuron #1 preganglionic presynaptic neuron #2 Ganglionic postsynaptic effector Preganglionic fiber (=axon): Always myelinated Postganglionic fiber: Always unmyelinated Fig 17.3 ?

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?

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

Special Case: Adrenal medulla Fig 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

Sympathetic Neuroeffector Junctions Differ from somatic neuromuscular junctions Varicosities

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

Para – Sympathetic Division 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 ?

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

PARASYMPATHETIC INNERVATION

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

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

INNERVATION OF THE BLADDER

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.

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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