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

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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

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Chain Ganglia

• Synapse within same chain ganglion

• Ascend or descend then synapse in chain ganglion

• Pass through chain ganglion without synapsing– Collateral ganglia

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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

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Adrenal Medulla

• Inner portion of the adrenal gland

• Largest sympathetic ganglia– Chromaffin cells • Secrete

norepinephrine and epinephrine into blood stream wikis.lib.ncsu.edu