AUTONOMIC AUTONOMIC NERVOUS SYSTEMNERVOUS SYSTEM

AUTONOMIC AUTONOMIC NERVOUS SYSTEMNERVOUS SYSTEM

BYBYDR.A.A.OREMOSUDR.A.A.OREMOSU

DEARTMENT OF ANATOMYDEARTMENT OF ANATOMYCMULCMUL

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-craniosacralSympathetic outflow-thoracolumbar

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 @ 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 myelinatedPostganglionic 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 columnParavertebral ganglia = sympathetic chain gangliaPrevertebral 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. 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

Sympathetic Neuroeffector

Junctions

Differ from somatic Differ from somatic neuromuscular neuromuscular junctionsjunctions

VaricositiesVaricosities

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 – SympatheticDivision

CraniosacralCraniosacral division division

Preganglionic neurons (cell bodies) Preganglionic neurons (cell bodies) located in brain stem & sacral segments of located in brain stem & sacral segments of spinal cordspinal cord

Ganglionic neurons (cell bodies) in ganglia Ganglionic neurons (cell bodies) in ganglia near target organs: near target organs: Intramural gangliaIntramural ganglia

Effects of parasympathetic division ?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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