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Transcript
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
• 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
?
Fig 17.3
Naming of neurons:
neuron #1
preganglionic
presynaptic
Preganglionic fiber
(=axon):
Always myelinated
neuron #2
Ganglionic
postsynaptic
Postganglionic fiber:
Always unmyelinated
effector
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:
Fig. 17-6
Adrenal medulla
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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