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Ch. 15The Autonomic Nervous System
Objectives• Know the general function of the ANS
• Be able to describe the characteristics of the ANS
• Know the two divisions of the ANS
• Be able to describe the anatomical differences between the parasympathetic and sympathetic systems
• Know the role of the adrenal medulla in the sympathetic system
Divisions of Nervous System
legacy.owensboro.kctcs.edu
Autonomic Nervous System
• System of motor neurons that innervates smooth, cardiac muscle, and glands
• Involuntary nervous system
• General visceral motor system
Characteristics• Effectors
– Cardiac and smooth muscle– Glands
• Efferent Pathway– Involves two neurons
• Ganglia– Preganglionic neuron > preganglionic axon > ganglionic neuron
> postganglionic axon > effector
• Neurotransmitter– All preganglionic neurons release acetylcholine– Norepinephrine, acetylcholine– Excitatory, inhibitory
Divisions of ANS• Sympathetic
– Fight or flight– Norepinephrine– Adrenergic fibers
• Parasympathetic– Rest and digest– Acetylcholine– Cholinergic fibers
• Dual innervation– Counterbalance– Tonic activity
• Ongoing activity of both divisionsvirtual.yosemite.cc.ca.us
Parasympathetic Division• Anatomically simpler
• Craniosacral origin– Cranial nerves III, VII, IX, X
• Oculomotor– Smooth muscle
• Facial– Lacrimal and mucus glands– Salivary glands
• Glossopharyngeal– Parotid glands
• Vagus– Innervates thoracic and abdominal
viscera
– Splanchnic nerves S2 - S4• Innervate pelvic organs antranik.org
Sympathetic Division
• Anatomically more complex– Innervates more organs
• Thoracolumbar origins– T1 – L2
• Sympathetic trunk ganglia– Paravertebral ganglia
studyblue.com
Chain Ganglia
• Synapse within same chain ganglion
• Ascend or descend then synapse in chain ganglion
• Pass through chain ganglion without synapsing– Collateral ganglia
anatomy.med.umich.edu
Sympathetic Chain Ganglia
• 22-24 chain ganglia
• Collateral ganglia– Unpaired – Only in abdomen and
pelvis– Lie on abdominal aorta• Celiac, sup. and inf.
Mesenteric, inf. hypogastric
wps.aw.com
Adrenal Medulla
• Inner portion of the adrenal gland
• Largest sympathetic ganglia– Chromaffin cells • Secrete
norepinephrine and epinephrine into blood stream wikis.lib.ncsu.edu