Ch. 15 The Autonomic Nervous System. Objectives Know the general function of the ANS Be able to describe the characteristics of the ANS Know the two divisions.

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