1. Autonomic Nervous System
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2. Figure 7.2 Organization of the nervous system.
Central Nervous System (brain and spinal cord)
Peripheral Nervous System (cranial and spinal nerves)
Sensory (afferent)
Motor (efferent)
Sense organs
Somatic (voluntary)
Autonomic (involuntary)
Skeletal muscles
Cardiac and smooth muscle, glands
Parasympathetic
Sympathetic

3. PNS: Autonomic Nervous System
ANS function: maintain homeostasis/internal stability
Involuntary regulation of
Cardiac activity
Smooth muscles/glands
Two subdivisions:
Sympathetic division
Parasympathetic division
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4. Motor Pathways of the ANS
The ANS has a chain of two motor neurons
Preganglionic neuron : in CNS (brain/spinal cord)
Axon is myelinated
Postganglionic neuron: in PNS
Extends to a specific organ
Axon is un-myelinated = slower response
This arrangement is different from the somatic division (voluntary motor division) which has only one myelinated motor neuron

5. Figure 7.27 Comparison of the somatic and autonomic nervous systems.
Central nervous system
Peripheral nervous system
Effector organs
Acetylcholine
Somatic nervous system
Skeletal muscle
Acetylcholine
Norepinephrine
Smooth muscle (e.g., in stomach)
Sympathetic division
Ganglion
Acetylcholine
Epinephrine and norepinephrine
Autonomic nervous system
Blood vessel
Glands
Acetylcholine
Para- sympathetic division
Cardiac muscle
Ganglion
KEY:
Preganglionic axons (sympathetic)
Postganglionic axons (sympathetic)
Myelination
Preganglionic axons (parasympathetic)
Postganglionic axons (parasympathetic)

6. How the neurotransmitters work
Acetylcholine (Ach) is released in both divisions
ACh is released by the Parasympathetic division to stimulate the effector directly
ACh is released by the Sympathetic division to cause a release of:
Epinephrine by the adrenal gland
Norepinephrine by the postganglionic nerve fibers
Either of these neurotransmitters will stimulate the effector (heart, blood vessel, gland…)

7. Comparison of the subdivisions: both serve the same organs with opposite effects
PARASYMPATHETIC
Relaxes
Conserves
Neurotransmitter at work is ACh
SYMPATHETIC
Mobilizes
Triggers:
Fear, exercise, rage
Neurotransmitters at work are
Epinephrine
Norepinephrine
Acetylcholine
REST/DIGEST
FIGHT/FLIGHT

8. PNS: Differences Between Somatic and Autonomic Nervous Systems
Somatic Nervous System
Autonomic Nervous System
Nerves
One-neuron system; it originates in the CNS, and axons extend to the skeletal muscles served
Two-neuron system consisting of preganglionic and postganglionic neurons
Effector organ
Skeletal muscle
Smooth muscle, cardiac muscle, glands
Subdivisions
None
Sympathetic and parasympathetic
Neurotransmitter
Acetylcholine
Acetylcholine, epinephrine (adrenaline), norepinephrine
© 2015 Pearson Education, Inc.