AUTONOMIC NERVOUS SYSTEM BY DR A A OREMOSU

AUTONOMIC NERVOUS SYSTEM BY DR. 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 • T 1 - L 2(3) • Supplies almost all viscera • Sympathetic chain 3 cervical, 10 -12 thoracic, 4 lummbar, 4 -5 sacral, I coccygeal ganglia • The 2 chain unite @ ganglion impar in front of coccyx

Schematic representation of the ANS

Synapsing takes place in ganglia ? Naming of neurons: neuron #1 preganglionic presynaptic Preganglionic fiber (=axon): Always myelinated Fig 17. 3 neuron #2 Ganglionic postsynaptic Postganglionic fiber: Always unmyelinated effector

Sympathetic Division Thoracolumbar division Preganglionic neurons (cell bodies) located between T 1 & L 2 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) T 5 -9 • Lesser splanchnic (LS) T 10 -11 • Least splanchnic (Le. S) T 12 Fibres pass through sympathetic chain without relaying End in ganglia GS-coeliac LS-superior mesenteric Le. S-may be absent-superior mesenteric

Special Case: Fig. 17 -6 Adrenal medulla Modified sympathetic ganglion Terminus for neuron #1, stimulates specialized 2 nd 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 S 2, 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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