Autonomic Nervous System Chapter 15. Autonomic Nervous System.
AUTONOMIC NERVOUS SYSTEM BYDR.A.A.OREMOSU DEARTMENT OF ANATOMY CMUL.
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Transcript of AUTONOMIC NERVOUS SYSTEM BYDR.A.A.OREMOSU DEARTMENT OF ANATOMY CMUL.
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
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
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
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
• 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
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